Merge branch 'linux-next' of git://git.kernel.org/pub/scm/linux/kernel/git/konrad...

[linux-2.6-microblaze.git] / drivers / pci / controller / pci-hyperv.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (c) Microsoft Corporation.
 *
 * Author:
 *   Jake Oshins <jakeo@microsoft.com>
 *
 * This driver acts as a paravirtual front-end for PCI Express root buses.
 * When a PCI Express function (either an entire device or an SR-IOV
 * Virtual Function) is being passed through to the VM, this driver exposes
 * a new bus to the guest VM.  This is modeled as a root PCI bus because
 * no bridges are being exposed to the VM.  In fact, with a "Generation 2"
 * VM within Hyper-V, there may seem to be no PCI bus at all in the VM
 * until a device as been exposed using this driver.
 *
 * Each root PCI bus has its own PCI domain, which is called "Segment" in
 * the PCI Firmware Specifications.  Thus while each device passed through
 * to the VM using this front-end will appear at "device 0", the domain will
 * be unique.  Typically, each bus will have one PCI function on it, though
 * this driver does support more than one.
 *
 * In order to map the interrupts from the device through to the guest VM,
 * this driver also implements an IRQ Domain, which handles interrupts (either
 * MSI or MSI-X) associated with the functions on the bus.  As interrupts are
 * set up, torn down, or reaffined, this driver communicates with the
 * underlying hypervisor to adjust the mappings in the I/O MMU so that each
 * interrupt will be delivered to the correct virtual processor at the right
 * vector.  This driver does not support level-triggered (line-based)
 * interrupts, and will report that the Interrupt Line register in the
 * function's configuration space is zero.
 *
 * The rest of this driver mostly maps PCI concepts onto underlying Hyper-V
 * facilities.  For instance, the configuration space of a function exposed
 * by Hyper-V is mapped into a single page of memory space, and the
 * read and write handlers for config space must be aware of this mechanism.
 * Similarly, device setup and teardown involves messages sent to and from
 * the PCI back-end driver in Hyper-V.
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/pci.h>
#include <linux/delay.h>
#include <linux/semaphore.h>
#include <linux/irqdomain.h>
#include <asm/irqdomain.h>
#include <asm/apic.h>
#include <linux/irq.h>
#include <linux/msi.h>
#include <linux/hyperv.h>
#include <linux/refcount.h>
#include <asm/mshyperv.h>

/*
 * Protocol versions. The low word is the minor version, the high word the
 * major version.
 */

#define PCI_MAKE_VERSION(major, minor) ((u32)(((major) << 16) | (minor)))
#define PCI_MAJOR_VERSION(version) ((u32)(version) >> 16)
#define PCI_MINOR_VERSION(version) ((u32)(version) & 0xff)

enum pci_protocol_version_t {
        PCI_PROTOCOL_VERSION_1_1 = PCI_MAKE_VERSION(1, 1),      /* Win10 */
        PCI_PROTOCOL_VERSION_1_2 = PCI_MAKE_VERSION(1, 2),      /* RS1 */
        PCI_PROTOCOL_VERSION_1_3 = PCI_MAKE_VERSION(1, 3),      /* Vibranium */
};

#define CPU_AFFINITY_ALL        -1ULL

/*
 * Supported protocol versions in the order of probing - highest go
 * first.
 */
static enum pci_protocol_version_t pci_protocol_versions[] = {
        PCI_PROTOCOL_VERSION_1_3,
        PCI_PROTOCOL_VERSION_1_2,
        PCI_PROTOCOL_VERSION_1_1,
};

#define PCI_CONFIG_MMIO_LENGTH  0x2000
#define CFG_PAGE_OFFSET 0x1000
#define CFG_PAGE_SIZE (PCI_CONFIG_MMIO_LENGTH - CFG_PAGE_OFFSET)

#define MAX_SUPPORTED_MSI_MESSAGES 0x400

#define STATUS_REVISION_MISMATCH 0xC0000059

/* space for 32bit serial number as string */
#define SLOT_NAME_SIZE 11

/*
 * Message Types
 */

enum pci_message_type {
        /*
         * Version 1.1
         */
        PCI_MESSAGE_BASE                = 0x42490000,
        PCI_BUS_RELATIONS               = PCI_MESSAGE_BASE + 0,
        PCI_QUERY_BUS_RELATIONS         = PCI_MESSAGE_BASE + 1,
        PCI_POWER_STATE_CHANGE          = PCI_MESSAGE_BASE + 4,
        PCI_QUERY_RESOURCE_REQUIREMENTS = PCI_MESSAGE_BASE + 5,
        PCI_QUERY_RESOURCE_RESOURCES    = PCI_MESSAGE_BASE + 6,
        PCI_BUS_D0ENTRY                 = PCI_MESSAGE_BASE + 7,
        PCI_BUS_D0EXIT                  = PCI_MESSAGE_BASE + 8,
        PCI_READ_BLOCK                  = PCI_MESSAGE_BASE + 9,
        PCI_WRITE_BLOCK                 = PCI_MESSAGE_BASE + 0xA,
        PCI_EJECT                       = PCI_MESSAGE_BASE + 0xB,
        PCI_QUERY_STOP                  = PCI_MESSAGE_BASE + 0xC,
        PCI_REENABLE                    = PCI_MESSAGE_BASE + 0xD,
        PCI_QUERY_STOP_FAILED           = PCI_MESSAGE_BASE + 0xE,
        PCI_EJECTION_COMPLETE           = PCI_MESSAGE_BASE + 0xF,
        PCI_RESOURCES_ASSIGNED          = PCI_MESSAGE_BASE + 0x10,
        PCI_RESOURCES_RELEASED          = PCI_MESSAGE_BASE + 0x11,
        PCI_INVALIDATE_BLOCK            = PCI_MESSAGE_BASE + 0x12,
        PCI_QUERY_PROTOCOL_VERSION      = PCI_MESSAGE_BASE + 0x13,
        PCI_CREATE_INTERRUPT_MESSAGE    = PCI_MESSAGE_BASE + 0x14,
        PCI_DELETE_INTERRUPT_MESSAGE    = PCI_MESSAGE_BASE + 0x15,
        PCI_RESOURCES_ASSIGNED2         = PCI_MESSAGE_BASE + 0x16,
        PCI_CREATE_INTERRUPT_MESSAGE2   = PCI_MESSAGE_BASE + 0x17,
        PCI_DELETE_INTERRUPT_MESSAGE2   = PCI_MESSAGE_BASE + 0x18, /* unused */
        PCI_BUS_RELATIONS2              = PCI_MESSAGE_BASE + 0x19,
        PCI_MESSAGE_MAXIMUM
};

/*
 * Structures defining the virtual PCI Express protocol.
 */

union pci_version {
        struct {
                u16 minor_version;
                u16 major_version;
        } parts;
        u32 version;
} __packed;

/*
 * Function numbers are 8-bits wide on Express, as interpreted through ARI,
 * which is all this driver does.  This representation is the one used in
 * Windows, which is what is expected when sending this back and forth with
 * the Hyper-V parent partition.
 */
union win_slot_encoding {
        struct {
                u32     dev:5;
                u32     func:3;
                u32     reserved:24;
        } bits;
        u32 slot;
} __packed;

/*
 * Pretty much as defined in the PCI Specifications.
 */
struct pci_function_description {
        u16     v_id;   /* vendor ID */
        u16     d_id;   /* device ID */
        u8      rev;
        u8      prog_intf;
        u8      subclass;
        u8      base_class;
        u32     subsystem_id;
        union win_slot_encoding win_slot;
        u32     ser;    /* serial number */
} __packed;

enum pci_device_description_flags {
        HV_PCI_DEVICE_FLAG_NONE                 = 0x0,
        HV_PCI_DEVICE_FLAG_NUMA_AFFINITY        = 0x1,
};

struct pci_function_description2 {
        u16     v_id;   /* vendor ID */
        u16     d_id;   /* device ID */
        u8      rev;
        u8      prog_intf;
        u8      subclass;
        u8      base_class;
        u32     subsystem_id;
        union   win_slot_encoding win_slot;
        u32     ser;    /* serial number */
        u32     flags;
        u16     virtual_numa_node;
        u16     reserved;
} __packed;

/**
 * struct hv_msi_desc
 * @vector:             IDT entry
 * @delivery_mode:      As defined in Intel's Programmer's
 *                      Reference Manual, Volume 3, Chapter 8.
 * @vector_count:       Number of contiguous entries in the
 *                      Interrupt Descriptor Table that are
 *                      occupied by this Message-Signaled
 *                      Interrupt. For "MSI", as first defined
 *                      in PCI 2.2, this can be between 1 and
 *                      32. For "MSI-X," as first defined in PCI
 *                      3.0, this must be 1, as each MSI-X table
 *                      entry would have its own descriptor.
 * @reserved:           Empty space
 * @cpu_mask:           All the target virtual processors.
 */
struct hv_msi_desc {
        u8      vector;
        u8      delivery_mode;
        u16     vector_count;
        u32     reserved;
        u64     cpu_mask;
} __packed;

/**
 * struct hv_msi_desc2 - 1.2 version of hv_msi_desc
 * @vector:             IDT entry
 * @delivery_mode:      As defined in Intel's Programmer's
 *                      Reference Manual, Volume 3, Chapter 8.
 * @vector_count:       Number of contiguous entries in the
 *                      Interrupt Descriptor Table that are
 *                      occupied by this Message-Signaled
 *                      Interrupt. For "MSI", as first defined
 *                      in PCI 2.2, this can be between 1 and
 *                      32. For "MSI-X," as first defined in PCI
 *                      3.0, this must be 1, as each MSI-X table
 *                      entry would have its own descriptor.
 * @processor_count:    number of bits enabled in array.
 * @processor_array:    All the target virtual processors.
 */
struct hv_msi_desc2 {
        u8      vector;
        u8      delivery_mode;
        u16     vector_count;
        u16     processor_count;
        u16     processor_array[32];
} __packed;

/**
 * struct tran_int_desc
 * @reserved:           unused, padding
 * @vector_count:       same as in hv_msi_desc
 * @data:               This is the "data payload" value that is
 *                      written by the device when it generates
 *                      a message-signaled interrupt, either MSI
 *                      or MSI-X.
 * @address:            This is the address to which the data
 *                      payload is written on interrupt
 *                      generation.
 */
struct tran_int_desc {
        u16     reserved;
        u16     vector_count;
        u32     data;
        u64     address;
} __packed;

/*
 * A generic message format for virtual PCI.
 * Specific message formats are defined later in the file.
 */

struct pci_message {
        u32 type;
} __packed;

struct pci_child_message {
        struct pci_message message_type;
        union win_slot_encoding wslot;
} __packed;

struct pci_incoming_message {
        struct vmpacket_descriptor hdr;
        struct pci_message message_type;
} __packed;

struct pci_response {
        struct vmpacket_descriptor hdr;
        s32 status;                     /* negative values are failures */
} __packed;

struct pci_packet {
        void (*completion_func)(void *context, struct pci_response *resp,
                                int resp_packet_size);
        void *compl_ctxt;

        struct pci_message message[];
};

/*
 * Specific message types supporting the PCI protocol.
 */

/*
 * Version negotiation message. Sent from the guest to the host.
 * The guest is free to try different versions until the host
 * accepts the version.
 *
 * pci_version: The protocol version requested.
 * is_last_attempt: If TRUE, this is the last version guest will request.
 * reservedz: Reserved field, set to zero.
 */

struct pci_version_request {
        struct pci_message message_type;
        u32 protocol_version;
} __packed;

/*
 * Bus D0 Entry.  This is sent from the guest to the host when the virtual
 * bus (PCI Express port) is ready for action.
 */

struct pci_bus_d0_entry {
        struct pci_message message_type;
        u32 reserved;
        u64 mmio_base;
} __packed;

struct pci_bus_relations {
        struct pci_incoming_message incoming;
        u32 device_count;
        struct pci_function_description func[];
} __packed;

struct pci_bus_relations2 {
        struct pci_incoming_message incoming;
        u32 device_count;
        struct pci_function_description2 func[];
} __packed;

struct pci_q_res_req_response {
        struct vmpacket_descriptor hdr;
        s32 status;                     /* negative values are failures */
        u32 probed_bar[PCI_STD_NUM_BARS];
} __packed;

struct pci_set_power {
        struct pci_message message_type;
        union win_slot_encoding wslot;
        u32 power_state;                /* In Windows terms */
        u32 reserved;
} __packed;

struct pci_set_power_response {
        struct vmpacket_descriptor hdr;
        s32 status;                     /* negative values are failures */
        union win_slot_encoding wslot;
        u32 resultant_state;            /* In Windows terms */
        u32 reserved;
} __packed;

struct pci_resources_assigned {
        struct pci_message message_type;
        union win_slot_encoding wslot;
        u8 memory_range[0x14][6];       /* not used here */
        u32 msi_descriptors;
        u32 reserved[4];
} __packed;

struct pci_resources_assigned2 {
        struct pci_message message_type;
        union win_slot_encoding wslot;
        u8 memory_range[0x14][6];       /* not used here */
        u32 msi_descriptor_count;
        u8 reserved[70];
} __packed;

struct pci_create_interrupt {
        struct pci_message message_type;
        union win_slot_encoding wslot;
        struct hv_msi_desc int_desc;
} __packed;

struct pci_create_int_response {
        struct pci_response response;
        u32 reserved;
        struct tran_int_desc int_desc;
} __packed;

struct pci_create_interrupt2 {
        struct pci_message message_type;
        union win_slot_encoding wslot;
        struct hv_msi_desc2 int_desc;
} __packed;

struct pci_delete_interrupt {
        struct pci_message message_type;
        union win_slot_encoding wslot;
        struct tran_int_desc int_desc;
} __packed;

/*
 * Note: the VM must pass a valid block id, wslot and bytes_requested.
 */
struct pci_read_block {
        struct pci_message message_type;
        u32 block_id;
        union win_slot_encoding wslot;
        u32 bytes_requested;
} __packed;

struct pci_read_block_response {
        struct vmpacket_descriptor hdr;
        u32 status;
        u8 bytes[HV_CONFIG_BLOCK_SIZE_MAX];
} __packed;

/*
 * Note: the VM must pass a valid block id, wslot and byte_count.
 */
struct pci_write_block {
        struct pci_message message_type;
        u32 block_id;
        union win_slot_encoding wslot;
        u32 byte_count;
        u8 bytes[HV_CONFIG_BLOCK_SIZE_MAX];
} __packed;

struct pci_dev_inval_block {
        struct pci_incoming_message incoming;
        union win_slot_encoding wslot;
        u64 block_mask;
} __packed;

struct pci_dev_incoming {
        struct pci_incoming_message incoming;
        union win_slot_encoding wslot;
} __packed;

struct pci_eject_response {
        struct pci_message message_type;
        union win_slot_encoding wslot;
        u32 status;
} __packed;

static int pci_ring_size = (4 * PAGE_SIZE);

/*
 * Driver specific state.
 */

enum hv_pcibus_state {
        hv_pcibus_init = 0,
        hv_pcibus_probed,
        hv_pcibus_installed,
        hv_pcibus_removing,
        hv_pcibus_maximum
};

struct hv_pcibus_device {
        struct pci_sysdata sysdata;
        /* Protocol version negotiated with the host */
        enum pci_protocol_version_t protocol_version;
        enum hv_pcibus_state state;
        struct hv_device *hdev;
        resource_size_t low_mmio_space;
        resource_size_t high_mmio_space;
        struct resource *mem_config;
        struct resource *low_mmio_res;
        struct resource *high_mmio_res;
        struct completion *survey_event;
        struct pci_bus *pci_bus;
        spinlock_t config_lock; /* Avoid two threads writing index page */
        spinlock_t device_list_lock;    /* Protect lists below */
        void __iomem *cfg_addr;

        struct list_head resources_for_children;

        struct list_head children;
        struct list_head dr_list;

        struct msi_domain_info msi_info;
        struct irq_domain *irq_domain;

        spinlock_t retarget_msi_interrupt_lock;

        struct workqueue_struct *wq;

        /* Highest slot of child device with resources allocated */
        int wslot_res_allocated;

        /* hypercall arg, must not cross page boundary */
        struct hv_retarget_device_interrupt retarget_msi_interrupt_params;

        /*
         * Don't put anything here: retarget_msi_interrupt_params must be last
         */
};

/*
 * Tracks "Device Relations" messages from the host, which must be both
 * processed in order and deferred so that they don't run in the context
 * of the incoming packet callback.
 */
struct hv_dr_work {
        struct work_struct wrk;
        struct hv_pcibus_device *bus;
};

struct hv_pcidev_description {
        u16     v_id;   /* vendor ID */
        u16     d_id;   /* device ID */
        u8      rev;
        u8      prog_intf;
        u8      subclass;
        u8      base_class;
        u32     subsystem_id;
        union   win_slot_encoding win_slot;
        u32     ser;    /* serial number */
        u32     flags;
        u16     virtual_numa_node;
};

struct hv_dr_state {
        struct list_head list_entry;
        u32 device_count;
        struct hv_pcidev_description func[];
};

enum hv_pcichild_state {
        hv_pcichild_init = 0,
        hv_pcichild_requirements,
        hv_pcichild_resourced,
        hv_pcichild_ejecting,
        hv_pcichild_maximum
};

struct hv_pci_dev {
        /* List protected by pci_rescan_remove_lock */
        struct list_head list_entry;
        refcount_t refs;
        enum hv_pcichild_state state;
        struct pci_slot *pci_slot;
        struct hv_pcidev_description desc;
        bool reported_missing;
        struct hv_pcibus_device *hbus;
        struct work_struct wrk;

        void (*block_invalidate)(void *context, u64 block_mask);
        void *invalidate_context;

        /*
         * What would be observed if one wrote 0xFFFFFFFF to a BAR and then
         * read it back, for each of the BAR offsets within config space.
         */
        u32 probed_bar[PCI_STD_NUM_BARS];
};

struct hv_pci_compl {
        struct completion host_event;
        s32 completion_status;
};

static void hv_pci_onchannelcallback(void *context);

/**
 * hv_pci_generic_compl() - Invoked for a completion packet
 * @context:            Set up by the sender of the packet.
 * @resp:               The response packet
 * @resp_packet_size:   Size in bytes of the packet
 *
 * This function is used to trigger an event and report status
 * for any message for which the completion packet contains a
 * status and nothing else.
 */
static void hv_pci_generic_compl(void *context, struct pci_response *resp,
                                 int resp_packet_size)
{
        struct hv_pci_compl *comp_pkt = context;

        if (resp_packet_size >= offsetofend(struct pci_response, status))
                comp_pkt->completion_status = resp->status;
        else
                comp_pkt->completion_status = -1;

        complete(&comp_pkt->host_event);
}

static struct hv_pci_dev *get_pcichild_wslot(struct hv_pcibus_device *hbus,
                                                u32 wslot);

static void get_pcichild(struct hv_pci_dev *hpdev)
{
        refcount_inc(&hpdev->refs);
}

static void put_pcichild(struct hv_pci_dev *hpdev)
{
        if (refcount_dec_and_test(&hpdev->refs))
                kfree(hpdev);
}

/*
 * There is no good way to get notified from vmbus_onoffer_rescind(),
 * so let's use polling here, since this is not a hot path.
 */
static int wait_for_response(struct hv_device *hdev,
                             struct completion *comp)
{
        while (true) {
                if (hdev->channel->rescind) {
                        dev_warn_once(&hdev->device, "The device is gone.\n");
                        return -ENODEV;
                }

                if (wait_for_completion_timeout(comp, HZ / 10))
                        break;
        }

        return 0;
}

/**
 * devfn_to_wslot() - Convert from Linux PCI slot to Windows
 * @devfn:      The Linux representation of PCI slot
 *
 * Windows uses a slightly different representation of PCI slot.
 *
 * Return: The Windows representation
 */
static u32 devfn_to_wslot(int devfn)
{
        union win_slot_encoding wslot;

        wslot.slot = 0;
        wslot.bits.dev = PCI_SLOT(devfn);
        wslot.bits.func = PCI_FUNC(devfn);

        return wslot.slot;
}

/**
 * wslot_to_devfn() - Convert from Windows PCI slot to Linux
 * @wslot:      The Windows representation of PCI slot
 *
 * Windows uses a slightly different representation of PCI slot.
 *
 * Return: The Linux representation
 */
static int wslot_to_devfn(u32 wslot)
{
        union win_slot_encoding slot_no;

        slot_no.slot = wslot;
        return PCI_DEVFN(slot_no.bits.dev, slot_no.bits.func);
}

/*
 * PCI Configuration Space for these root PCI buses is implemented as a pair
 * of pages in memory-mapped I/O space.  Writing to the first page chooses
 * the PCI function being written or read.  Once the first page has been
 * written to, the following page maps in the entire configuration space of
 * the function.
 */

/**
 * _hv_pcifront_read_config() - Internal PCI config read
 * @hpdev:      The PCI driver's representation of the device
 * @where:      Offset within config space
 * @size:       Size of the transfer
 * @val:        Pointer to the buffer receiving the data
 */
static void _hv_pcifront_read_config(struct hv_pci_dev *hpdev, int where,
                                     int size, u32 *val)
{
        unsigned long flags;
        void __iomem *addr = hpdev->hbus->cfg_addr + CFG_PAGE_OFFSET + where;

        /*
         * If the attempt is to read the IDs or the ROM BAR, simulate that.
         */
        if (where + size <= PCI_COMMAND) {
                memcpy(val, ((u8 *)&hpdev->desc.v_id) + where, size);
        } else if (where >= PCI_CLASS_REVISION && where + size <=
                   PCI_CACHE_LINE_SIZE) {
                memcpy(val, ((u8 *)&hpdev->desc.rev) + where -
                       PCI_CLASS_REVISION, size);
        } else if (where >= PCI_SUBSYSTEM_VENDOR_ID && where + size <=
                   PCI_ROM_ADDRESS) {
                memcpy(val, (u8 *)&hpdev->desc.subsystem_id + where -
                       PCI_SUBSYSTEM_VENDOR_ID, size);
        } else if (where >= PCI_ROM_ADDRESS && where + size <=
                   PCI_CAPABILITY_LIST) {
                /* ROM BARs are unimplemented */
                *val = 0;
        } else if (where >= PCI_INTERRUPT_LINE && where + size <=
                   PCI_INTERRUPT_PIN) {
                /*
                 * Interrupt Line and Interrupt PIN are hard-wired to zero
                 * because this front-end only supports message-signaled
                 * interrupts.
                 */
                *val = 0;
        } else if (where + size <= CFG_PAGE_SIZE) {
                spin_lock_irqsave(&hpdev->hbus->config_lock, flags);
                /* Choose the function to be read. (See comment above) */
                writel(hpdev->desc.win_slot.slot, hpdev->hbus->cfg_addr);
                /* Make sure the function was chosen before we start reading. */
                mb();
                /* Read from that function's config space. */
                switch (size) {
                case 1:
                        *val = readb(addr);
                        break;
                case 2:
                        *val = readw(addr);
                        break;
                default:
                        *val = readl(addr);
                        break;
                }
                /*
                 * Make sure the read was done before we release the spinlock
                 * allowing consecutive reads/writes.
                 */
                mb();
                spin_unlock_irqrestore(&hpdev->hbus->config_lock, flags);
        } else {
                dev_err(&hpdev->hbus->hdev->device,
                        "Attempt to read beyond a function's config space.\n");
        }
}

static u16 hv_pcifront_get_vendor_id(struct hv_pci_dev *hpdev)
{
        u16 ret;
        unsigned long flags;
        void __iomem *addr = hpdev->hbus->cfg_addr + CFG_PAGE_OFFSET +
                             PCI_VENDOR_ID;

        spin_lock_irqsave(&hpdev->hbus->config_lock, flags);

        /* Choose the function to be read. (See comment above) */
        writel(hpdev->desc.win_slot.slot, hpdev->hbus->cfg_addr);
        /* Make sure the function was chosen before we start reading. */
        mb();
        /* Read from that function's config space. */
        ret = readw(addr);
        /*
         * mb() is not required here, because the spin_unlock_irqrestore()
         * is a barrier.
         */

        spin_unlock_irqrestore(&hpdev->hbus->config_lock, flags);

        return ret;
}

/**
 * _hv_pcifront_write_config() - Internal PCI config write
 * @hpdev:      The PCI driver's representation of the device
 * @where:      Offset within config space
 * @size:       Size of the transfer
 * @val:        The data being transferred
 */
static void _hv_pcifront_write_config(struct hv_pci_dev *hpdev, int where,
                                      int size, u32 val)
{
        unsigned long flags;
        void __iomem *addr = hpdev->hbus->cfg_addr + CFG_PAGE_OFFSET + where;

        if (where >= PCI_SUBSYSTEM_VENDOR_ID &&
            where + size <= PCI_CAPABILITY_LIST) {
                /* SSIDs and ROM BARs are read-only */
        } else if (where >= PCI_COMMAND && where + size <= CFG_PAGE_SIZE) {
                spin_lock_irqsave(&hpdev->hbus->config_lock, flags);
                /* Choose the function to be written. (See comment above) */
                writel(hpdev->desc.win_slot.slot, hpdev->hbus->cfg_addr);
                /* Make sure the function was chosen before we start writing. */
                wmb();
                /* Write to that function's config space. */
                switch (size) {
                case 1:
                        writeb(val, addr);
                        break;
                case 2:
                        writew(val, addr);
                        break;
                default:
                        writel(val, addr);
                        break;
                }
                /*
                 * Make sure the write was done before we release the spinlock
                 * allowing consecutive reads/writes.
                 */
                mb();
                spin_unlock_irqrestore(&hpdev->hbus->config_lock, flags);
        } else {
                dev_err(&hpdev->hbus->hdev->device,
                        "Attempt to write beyond a function's config space.\n");
        }
}

/**
 * hv_pcifront_read_config() - Read configuration space
 * @bus: PCI Bus structure
 * @devfn: Device/function
 * @where: Offset from base
 * @size: Byte/word/dword
 * @val: Value to be read
 *
 * Return: PCIBIOS_SUCCESSFUL on success
 *         PCIBIOS_DEVICE_NOT_FOUND on failure
 */
static int hv_pcifront_read_config(struct pci_bus *bus, unsigned int devfn,
                                   int where, int size, u32 *val)
{
        struct hv_pcibus_device *hbus =
                container_of(bus->sysdata, struct hv_pcibus_device, sysdata);
        struct hv_pci_dev *hpdev;

        hpdev = get_pcichild_wslot(hbus, devfn_to_wslot(devfn));
        if (!hpdev)
                return PCIBIOS_DEVICE_NOT_FOUND;

        _hv_pcifront_read_config(hpdev, where, size, val);

        put_pcichild(hpdev);
        return PCIBIOS_SUCCESSFUL;
}

/**
 * hv_pcifront_write_config() - Write configuration space
 * @bus: PCI Bus structure
 * @devfn: Device/function
 * @where: Offset from base
 * @size: Byte/word/dword
 * @val: Value to be written to device
 *
 * Return: PCIBIOS_SUCCESSFUL on success
 *         PCIBIOS_DEVICE_NOT_FOUND on failure
 */
static int hv_pcifront_write_config(struct pci_bus *bus, unsigned int devfn,
                                    int where, int size, u32 val)
{
        struct hv_pcibus_device *hbus =
            container_of(bus->sysdata, struct hv_pcibus_device, sysdata);
        struct hv_pci_dev *hpdev;

        hpdev = get_pcichild_wslot(hbus, devfn_to_wslot(devfn));
        if (!hpdev)
                return PCIBIOS_DEVICE_NOT_FOUND;

        _hv_pcifront_write_config(hpdev, where, size, val);

        put_pcichild(hpdev);
        return PCIBIOS_SUCCESSFUL;
}

/* PCIe operations */
static struct pci_ops hv_pcifront_ops = {
        .read  = hv_pcifront_read_config,
        .write = hv_pcifront_write_config,
};

/*
 * Paravirtual backchannel
 *
 * Hyper-V SR-IOV provides a backchannel mechanism in software for
 * communication between a VF driver and a PF driver.  These
 * "configuration blocks" are similar in concept to PCI configuration space,
 * but instead of doing reads and writes in 32-bit chunks through a very slow
 * path, packets of up to 128 bytes can be sent or received asynchronously.
 *
 * Nearly every SR-IOV device contains just such a communications channel in
 * hardware, so using this one in software is usually optional.  Using the
 * software channel, however, allows driver implementers to leverage software
 * tools that fuzz the communications channel looking for vulnerabilities.
 *
 * The usage model for these packets puts the responsibility for reading or
 * writing on the VF driver.  The VF driver sends a read or a write packet,
 * indicating which "block" is being referred to by number.
 *
 * If the PF driver wishes to initiate communication, it can "invalidate" one or
 * more of the first 64 blocks.  This invalidation is delivered via a callback
 * supplied by the VF driver by this driver.
 *
 * No protocol is implied, except that supplied by the PF and VF drivers.
 */

struct hv_read_config_compl {
        struct hv_pci_compl comp_pkt;
        void *buf;
        unsigned int len;
        unsigned int bytes_returned;
};

/**
 * hv_pci_read_config_compl() - Invoked when a response packet
 * for a read config block operation arrives.
 * @context:            Identifies the read config operation
 * @resp:               The response packet itself
 * @resp_packet_size:   Size in bytes of the response packet
 */
static void hv_pci_read_config_compl(void *context, struct pci_response *resp,
                                     int resp_packet_size)
{
        struct hv_read_config_compl *comp = context;
        struct pci_read_block_response *read_resp =
                (struct pci_read_block_response *)resp;
        unsigned int data_len, hdr_len;

        hdr_len = offsetof(struct pci_read_block_response, bytes);
        if (resp_packet_size < hdr_len) {
                comp->comp_pkt.completion_status = -1;
                goto out;
        }

        data_len = resp_packet_size - hdr_len;
        if (data_len > 0 && read_resp->status == 0) {
                comp->bytes_returned = min(comp->len, data_len);
                memcpy(comp->buf, read_resp->bytes, comp->bytes_returned);
        } else {
                comp->bytes_returned = 0;
        }

        comp->comp_pkt.completion_status = read_resp->status;
out:
        complete(&comp->comp_pkt.host_event);
}

/**
 * hv_read_config_block() - Sends a read config block request to
 * the back-end driver running in the Hyper-V parent partition.
 * @pdev:               The PCI driver's representation for this device.
 * @buf:                Buffer into which the config block will be copied.
 * @len:                Size in bytes of buf.
 * @block_id:           Identifies the config block which has been requested.
 * @bytes_returned:     Size which came back from the back-end driver.
 *
 * Return: 0 on success, -errno on failure
 */
static int hv_read_config_block(struct pci_dev *pdev, void *buf,
                                unsigned int len, unsigned int block_id,
                                unsigned int *bytes_returned)
{
        struct hv_pcibus_device *hbus =
                container_of(pdev->bus->sysdata, struct hv_pcibus_device,
                             sysdata);
        struct {
                struct pci_packet pkt;
                char buf[sizeof(struct pci_read_block)];
        } pkt;
        struct hv_read_config_compl comp_pkt;
        struct pci_read_block *read_blk;
        int ret;

        if (len == 0 || len > HV_CONFIG_BLOCK_SIZE_MAX)
                return -EINVAL;

        init_completion(&comp_pkt.comp_pkt.host_event);
        comp_pkt.buf = buf;
        comp_pkt.len = len;

        memset(&pkt, 0, sizeof(pkt));
        pkt.pkt.completion_func = hv_pci_read_config_compl;
        pkt.pkt.compl_ctxt = &comp_pkt;
        read_blk = (struct pci_read_block *)&pkt.pkt.message;
        read_blk->message_type.type = PCI_READ_BLOCK;
        read_blk->wslot.slot = devfn_to_wslot(pdev->devfn);
        read_blk->block_id = block_id;
        read_blk->bytes_requested = len;

        ret = vmbus_sendpacket(hbus->hdev->channel, read_blk,
                               sizeof(*read_blk), (unsigned long)&pkt.pkt,
                               VM_PKT_DATA_INBAND,
                               VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED);
        if (ret)
                return ret;

        ret = wait_for_response(hbus->hdev, &comp_pkt.comp_pkt.host_event);
        if (ret)
                return ret;

        if (comp_pkt.comp_pkt.completion_status != 0 ||
            comp_pkt.bytes_returned == 0) {
                dev_err(&hbus->hdev->device,
                        "Read Config Block failed: 0x%x, bytes_returned=%d\n",
                        comp_pkt.comp_pkt.completion_status,
                        comp_pkt.bytes_returned);
                return -EIO;
        }

        *bytes_returned = comp_pkt.bytes_returned;
        return 0;
}

/**
 * hv_pci_write_config_compl() - Invoked when a response packet for a write
 * config block operation arrives.
 * @context:            Identifies the write config operation
 * @resp:               The response packet itself
 * @resp_packet_size:   Size in bytes of the response packet
 */
static void hv_pci_write_config_compl(void *context, struct pci_response *resp,
                                      int resp_packet_size)
{
        struct hv_pci_compl *comp_pkt = context;

        comp_pkt->completion_status = resp->status;
        complete(&comp_pkt->host_event);
}

/**
 * hv_write_config_block() - Sends a write config block request to the
 * back-end driver running in the Hyper-V parent partition.
 * @pdev:               The PCI driver's representation for this device.
 * @buf:                Buffer from which the config block will be copied.
 * @len:                Size in bytes of buf.
 * @block_id:           Identifies the config block which is being written.
 *
 * Return: 0 on success, -errno on failure
 */
static int hv_write_config_block(struct pci_dev *pdev, void *buf,
                                unsigned int len, unsigned int block_id)
{
        struct hv_pcibus_device *hbus =
                container_of(pdev->bus->sysdata, struct hv_pcibus_device,
                             sysdata);
        struct {
                struct pci_packet pkt;
                char buf[sizeof(struct pci_write_block)];
                u32 reserved;
        } pkt;
        struct hv_pci_compl comp_pkt;
        struct pci_write_block *write_blk;
        u32 pkt_size;
        int ret;

        if (len == 0 || len > HV_CONFIG_BLOCK_SIZE_MAX)
                return -EINVAL;

        init_completion(&comp_pkt.host_event);

        memset(&pkt, 0, sizeof(pkt));
        pkt.pkt.completion_func = hv_pci_write_config_compl;
        pkt.pkt.compl_ctxt = &comp_pkt;
        write_blk = (struct pci_write_block *)&pkt.pkt.message;
        write_blk->message_type.type = PCI_WRITE_BLOCK;
        write_blk->wslot.slot = devfn_to_wslot(pdev->devfn);
        write_blk->block_id = block_id;
        write_blk->byte_count = len;
        memcpy(write_blk->bytes, buf, len);
        pkt_size = offsetof(struct pci_write_block, bytes) + len;
        /*
         * This quirk is required on some hosts shipped around 2018, because
         * these hosts don't check the pkt_size correctly (new hosts have been
         * fixed since early 2019). The quirk is also safe on very old hosts
         * and new hosts, because, on them, what really matters is the length
         * specified in write_blk->byte_count.
         */
        pkt_size += sizeof(pkt.reserved);

        ret = vmbus_sendpacket(hbus->hdev->channel, write_blk, pkt_size,
                               (unsigned long)&pkt.pkt, VM_PKT_DATA_INBAND,
                               VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED);
        if (ret)
                return ret;

        ret = wait_for_response(hbus->hdev, &comp_pkt.host_event);
        if (ret)
                return ret;

        if (comp_pkt.completion_status != 0) {
                dev_err(&hbus->hdev->device,
                        "Write Config Block failed: 0x%x\n",
                        comp_pkt.completion_status);
                return -EIO;
        }

        return 0;
}

/**
 * hv_register_block_invalidate() - Invoked when a config block invalidation
 * arrives from the back-end driver.
 * @pdev:               The PCI driver's representation for this device.
 * @context:            Identifies the device.
 * @block_invalidate:   Identifies all of the blocks being invalidated.
 *
 * Return: 0 on success, -errno on failure
 */
static int hv_register_block_invalidate(struct pci_dev *pdev, void *context,
                                        void (*block_invalidate)(void *context,
                                                                 u64 block_mask))
{
        struct hv_pcibus_device *hbus =
                container_of(pdev->bus->sysdata, struct hv_pcibus_device,
                             sysdata);
        struct hv_pci_dev *hpdev;

        hpdev = get_pcichild_wslot(hbus, devfn_to_wslot(pdev->devfn));
        if (!hpdev)
                return -ENODEV;

        hpdev->block_invalidate = block_invalidate;
        hpdev->invalidate_context = context;

        put_pcichild(hpdev);
        return 0;

}

/* Interrupt management hooks */
static void hv_int_desc_free(struct hv_pci_dev *hpdev,
                             struct tran_int_desc *int_desc)
{
        struct pci_delete_interrupt *int_pkt;
        struct {
                struct pci_packet pkt;
                u8 buffer[sizeof(struct pci_delete_interrupt)];
        } ctxt;

        memset(&ctxt, 0, sizeof(ctxt));
        int_pkt = (struct pci_delete_interrupt *)&ctxt.pkt.message;
        int_pkt->message_type.type =
                PCI_DELETE_INTERRUPT_MESSAGE;
        int_pkt->wslot.slot = hpdev->desc.win_slot.slot;
        int_pkt->int_desc = *int_desc;
        vmbus_sendpacket(hpdev->hbus->hdev->channel, int_pkt, sizeof(*int_pkt),
                         (unsigned long)&ctxt.pkt, VM_PKT_DATA_INBAND, 0);
        kfree(int_desc);
}

/**
 * hv_msi_free() - Free the MSI.
 * @domain:     The interrupt domain pointer
 * @info:       Extra MSI-related context
 * @irq:        Identifies the IRQ.
 *
 * The Hyper-V parent partition and hypervisor are tracking the
 * messages that are in use, keeping the interrupt redirection
 * table up to date.  This callback sends a message that frees
 * the IRT entry and related tracking nonsense.
 */
static void hv_msi_free(struct irq_domain *domain, struct msi_domain_info *info,
                        unsigned int irq)
{
        struct hv_pcibus_device *hbus;
        struct hv_pci_dev *hpdev;
        struct pci_dev *pdev;
        struct tran_int_desc *int_desc;
        struct irq_data *irq_data = irq_domain_get_irq_data(domain, irq);
        struct msi_desc *msi = irq_data_get_msi_desc(irq_data);

        pdev = msi_desc_to_pci_dev(msi);
        hbus = info->data;
        int_desc = irq_data_get_irq_chip_data(irq_data);
        if (!int_desc)
                return;

        irq_data->chip_data = NULL;
        hpdev = get_pcichild_wslot(hbus, devfn_to_wslot(pdev->devfn));
        if (!hpdev) {
                kfree(int_desc);
                return;
        }

        hv_int_desc_free(hpdev, int_desc);
        put_pcichild(hpdev);
}

static int hv_set_affinity(struct irq_data *data, const struct cpumask *dest,
                           bool force)
{
        struct irq_data *parent = data->parent_data;

        return parent->chip->irq_set_affinity(parent, dest, force);
}

static void hv_irq_mask(struct irq_data *data)
{
        pci_msi_mask_irq(data);
}

/**
 * hv_irq_unmask() - "Unmask" the IRQ by setting its current
 * affinity.
 * @data:       Describes the IRQ
 *
 * Build new a destination for the MSI and make a hypercall to
 * update the Interrupt Redirection Table. "Device Logical ID"
 * is built out of this PCI bus's instance GUID and the function
 * number of the device.
 */
static void hv_irq_unmask(struct irq_data *data)
{
        struct msi_desc *msi_desc = irq_data_get_msi_desc(data);
        struct irq_cfg *cfg = irqd_cfg(data);
        struct hv_retarget_device_interrupt *params;
        struct hv_pcibus_device *hbus;
        struct cpumask *dest;
        cpumask_var_t tmp;
        struct pci_bus *pbus;
        struct pci_dev *pdev;
        unsigned long flags;
        u32 var_size = 0;
        int cpu, nr_bank;
        u64 res;

        dest = irq_data_get_effective_affinity_mask(data);
        pdev = msi_desc_to_pci_dev(msi_desc);
        pbus = pdev->bus;
        hbus = container_of(pbus->sysdata, struct hv_pcibus_device, sysdata);

        spin_lock_irqsave(&hbus->retarget_msi_interrupt_lock, flags);

        params = &hbus->retarget_msi_interrupt_params;
        memset(params, 0, sizeof(*params));
        params->partition_id = HV_PARTITION_ID_SELF;
        params->int_entry.source = HV_INTERRUPT_SOURCE_MSI;
        hv_set_msi_entry_from_desc(&params->int_entry.msi_entry, msi_desc);
        params->device_id = (hbus->hdev->dev_instance.b[5] << 24) |
                           (hbus->hdev->dev_instance.b[4] << 16) |
                           (hbus->hdev->dev_instance.b[7] << 8) |
                           (hbus->hdev->dev_instance.b[6] & 0xf8) |
                           PCI_FUNC(pdev->devfn);
        params->int_target.vector = cfg->vector;

        /*
         * Honoring apic->delivery_mode set to APIC_DELIVERY_MODE_FIXED by
         * setting the HV_DEVICE_INTERRUPT_TARGET_MULTICAST flag results in a
         * spurious interrupt storm. Not doing so does not seem to have a
         * negative effect (yet?).
         */

        if (hbus->protocol_version >= PCI_PROTOCOL_VERSION_1_2) {
                /*
                 * PCI_PROTOCOL_VERSION_1_2 supports the VP_SET version of the
                 * HVCALL_RETARGET_INTERRUPT hypercall, which also coincides
                 * with >64 VP support.
                 * ms_hyperv.hints & HV_X64_EX_PROCESSOR_MASKS_RECOMMENDED
                 * is not sufficient for this hypercall.
                 */
                params->int_target.flags |=
                        HV_DEVICE_INTERRUPT_TARGET_PROCESSOR_SET;

                if (!alloc_cpumask_var(&tmp, GFP_ATOMIC)) {
                        res = 1;
                        goto exit_unlock;
                }

                cpumask_and(tmp, dest, cpu_online_mask);
                nr_bank = cpumask_to_vpset(&params->int_target.vp_set, tmp);
                free_cpumask_var(tmp);

                if (nr_bank <= 0) {
                        res = 1;
                        goto exit_unlock;
                }

                /*
                 * var-sized hypercall, var-size starts after vp_mask (thus
                 * vp_set.format does not count, but vp_set.valid_bank_mask
                 * does).
                 */
                var_size = 1 + nr_bank;
        } else {
                for_each_cpu_and(cpu, dest, cpu_online_mask) {
                        params->int_target.vp_mask |=
                                (1ULL << hv_cpu_number_to_vp_number(cpu));
                }
        }

        res = hv_do_hypercall(HVCALL_RETARGET_INTERRUPT | (var_size << 17),
                              params, NULL);

exit_unlock:
        spin_unlock_irqrestore(&hbus->retarget_msi_interrupt_lock, flags);

        /*
         * During hibernation, when a CPU is offlined, the kernel tries
         * to move the interrupt to the remaining CPUs that haven't
         * been offlined yet. In this case, the below hv_do_hypercall()
         * always fails since the vmbus channel has been closed:
         * refer to cpu_disable_common() -> fixup_irqs() ->
         * irq_migrate_all_off_this_cpu() -> migrate_one_irq().
         *
         * Suppress the error message for hibernation because the failure
         * during hibernation does not matter (at this time all the devices
         * have been frozen). Note: the correct affinity info is still updated
         * into the irqdata data structure in migrate_one_irq() ->
         * irq_do_set_affinity() -> hv_set_affinity(), so later when the VM
         * resumes, hv_pci_restore_msi_state() is able to correctly restore
         * the interrupt with the correct affinity.
         */
        if (!hv_result_success(res) && hbus->state != hv_pcibus_removing)
                dev_err(&hbus->hdev->device,
                        "%s() failed: %#llx", __func__, res);

        pci_msi_unmask_irq(data);
}

struct compose_comp_ctxt {
        struct hv_pci_compl comp_pkt;
        struct tran_int_desc int_desc;
};

static void hv_pci_compose_compl(void *context, struct pci_response *resp,
                                 int resp_packet_size)
{
        struct compose_comp_ctxt *comp_pkt = context;
        struct pci_create_int_response *int_resp =
                (struct pci_create_int_response *)resp;

        comp_pkt->comp_pkt.completion_status = resp->status;
        comp_pkt->int_desc = int_resp->int_desc;
        complete(&comp_pkt->comp_pkt.host_event);
}

static u32 hv_compose_msi_req_v1(
        struct pci_create_interrupt *int_pkt, struct cpumask *affinity,
        u32 slot, u8 vector)
{
        int_pkt->message_type.type = PCI_CREATE_INTERRUPT_MESSAGE;
        int_pkt->wslot.slot = slot;
        int_pkt->int_desc.vector = vector;
        int_pkt->int_desc.vector_count = 1;
        int_pkt->int_desc.delivery_mode = APIC_DELIVERY_MODE_FIXED;

        /*
         * Create MSI w/ dummy vCPU set, overwritten by subsequent retarget in
         * hv_irq_unmask().
         */
        int_pkt->int_desc.cpu_mask = CPU_AFFINITY_ALL;

        return sizeof(*int_pkt);
}

static u32 hv_compose_msi_req_v2(
        struct pci_create_interrupt2 *int_pkt, struct cpumask *affinity,
        u32 slot, u8 vector)
{
        int cpu;

        int_pkt->message_type.type = PCI_CREATE_INTERRUPT_MESSAGE2;
        int_pkt->wslot.slot = slot;
        int_pkt->int_desc.vector = vector;
        int_pkt->int_desc.vector_count = 1;
        int_pkt->int_desc.delivery_mode = APIC_DELIVERY_MODE_FIXED;

        /*
         * Create MSI w/ dummy vCPU set targeting just one vCPU, overwritten
         * by subsequent retarget in hv_irq_unmask().
         */
        cpu = cpumask_first_and(affinity, cpu_online_mask);
        int_pkt->int_desc.processor_array[0] =
                hv_cpu_number_to_vp_number(cpu);
        int_pkt->int_desc.processor_count = 1;

        return sizeof(*int_pkt);
}

/**
 * hv_compose_msi_msg() - Supplies a valid MSI address/data
 * @data:       Everything about this MSI
 * @msg:        Buffer that is filled in by this function
 *
 * This function unpacks the IRQ looking for target CPU set, IDT
 * vector and mode and sends a message to the parent partition
 * asking for a mapping for that tuple in this partition.  The
 * response supplies a data value and address to which that data
 * should be written to trigger that interrupt.
 */
static void hv_compose_msi_msg(struct irq_data *data, struct msi_msg *msg)
{
        struct irq_cfg *cfg = irqd_cfg(data);
        struct hv_pcibus_device *hbus;
        struct vmbus_channel *channel;
        struct hv_pci_dev *hpdev;
        struct pci_bus *pbus;
        struct pci_dev *pdev;
        struct cpumask *dest;
        struct compose_comp_ctxt comp;
        struct tran_int_desc *int_desc;
        struct {
                struct pci_packet pci_pkt;
                union {
                        struct pci_create_interrupt v1;
                        struct pci_create_interrupt2 v2;
                } int_pkts;
        } __packed ctxt;

        u32 size;
        int ret;

        pdev = msi_desc_to_pci_dev(irq_data_get_msi_desc(data));
        dest = irq_data_get_effective_affinity_mask(data);
        pbus = pdev->bus;
        hbus = container_of(pbus->sysdata, struct hv_pcibus_device, sysdata);
        channel = hbus->hdev->channel;
        hpdev = get_pcichild_wslot(hbus, devfn_to_wslot(pdev->devfn));
        if (!hpdev)
                goto return_null_message;

        /* Free any previous message that might have already been composed. */
        if (data->chip_data) {
                int_desc = data->chip_data;
                data->chip_data = NULL;
                hv_int_desc_free(hpdev, int_desc);
        }

        int_desc = kzalloc(sizeof(*int_desc), GFP_ATOMIC);
        if (!int_desc)
                goto drop_reference;

        memset(&ctxt, 0, sizeof(ctxt));
        init_completion(&comp.comp_pkt.host_event);
        ctxt.pci_pkt.completion_func = hv_pci_compose_compl;
        ctxt.pci_pkt.compl_ctxt = &comp;

        switch (hbus->protocol_version) {
        case PCI_PROTOCOL_VERSION_1_1:
                size = hv_compose_msi_req_v1(&ctxt.int_pkts.v1,
                                        dest,
                                        hpdev->desc.win_slot.slot,
                                        cfg->vector);
                break;

        case PCI_PROTOCOL_VERSION_1_2:
        case PCI_PROTOCOL_VERSION_1_3:
                size = hv_compose_msi_req_v2(&ctxt.int_pkts.v2,
                                        dest,
                                        hpdev->desc.win_slot.slot,
                                        cfg->vector);
                break;

        default:
                /* As we only negotiate protocol versions known to this driver,
                 * this path should never hit. However, this is it not a hot
                 * path so we print a message to aid future updates.
                 */
                dev_err(&hbus->hdev->device,
                        "Unexpected vPCI protocol, update driver.");
                goto free_int_desc;
        }

        ret = vmbus_sendpacket(hpdev->hbus->hdev->channel, &ctxt.int_pkts,
                               size, (unsigned long)&ctxt.pci_pkt,
                               VM_PKT_DATA_INBAND,
                               VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED);
        if (ret) {
                dev_err(&hbus->hdev->device,
                        "Sending request for interrupt failed: 0x%x",
                        comp.comp_pkt.completion_status);
                goto free_int_desc;
        }

        /*
         * Prevents hv_pci_onchannelcallback() from running concurrently
         * in the tasklet.
         */
        tasklet_disable_in_atomic(&channel->callback_event);

        /*
         * Since this function is called with IRQ locks held, can't
         * do normal wait for completion; instead poll.
         */
        while (!try_wait_for_completion(&comp.comp_pkt.host_event)) {
                unsigned long flags;

                /* 0xFFFF means an invalid PCI VENDOR ID. */
                if (hv_pcifront_get_vendor_id(hpdev) == 0xFFFF) {
                        dev_err_once(&hbus->hdev->device,
                                     "the device has gone\n");
                        goto enable_tasklet;
                }

                /*
                 * Make sure that the ring buffer data structure doesn't get
                 * freed while we dereference the ring buffer pointer.  Test
                 * for the channel's onchannel_callback being NULL within a
                 * sched_lock critical section.  See also the inline comments
                 * in vmbus_reset_channel_cb().
                 */
                spin_lock_irqsave(&channel->sched_lock, flags);
                if (unlikely(channel->onchannel_callback == NULL)) {
                        spin_unlock_irqrestore(&channel->sched_lock, flags);
                        goto enable_tasklet;
                }
                hv_pci_onchannelcallback(hbus);
                spin_unlock_irqrestore(&channel->sched_lock, flags);

                if (hpdev->state == hv_pcichild_ejecting) {
                        dev_err_once(&hbus->hdev->device,
                                     "the device is being ejected\n");
                        goto enable_tasklet;
                }

                udelay(100);
        }

        tasklet_enable(&channel->callback_event);

        if (comp.comp_pkt.completion_status < 0) {
                dev_err(&hbus->hdev->device,
                        "Request for interrupt failed: 0x%x",
                        comp.comp_pkt.completion_status);
                goto free_int_desc;
        }

        /*
         * Record the assignment so that this can be unwound later. Using
         * irq_set_chip_data() here would be appropriate, but the lock it takes
         * is already held.
         */
        *int_desc = comp.int_desc;
        data->chip_data = int_desc;

        /* Pass up the result. */
        msg->address_hi = comp.int_desc.address >> 32;
        msg->address_lo = comp.int_desc.address & 0xffffffff;
        msg->data = comp.int_desc.data;

        put_pcichild(hpdev);
        return;

enable_tasklet:
        tasklet_enable(&channel->callback_event);
free_int_desc:
        kfree(int_desc);
drop_reference:
        put_pcichild(hpdev);
return_null_message:
        msg->address_hi = 0;
        msg->address_lo = 0;
        msg->data = 0;
}

/* HW Interrupt Chip Descriptor */
static struct irq_chip hv_msi_irq_chip = {
        .name                   = "Hyper-V PCIe MSI",
        .irq_compose_msi_msg    = hv_compose_msi_msg,
        .irq_set_affinity       = hv_set_affinity,
        .irq_ack                = irq_chip_ack_parent,
        .irq_mask               = hv_irq_mask,
        .irq_unmask             = hv_irq_unmask,
};

static struct msi_domain_ops hv_msi_ops = {
        .msi_prepare    = pci_msi_prepare,
        .msi_free       = hv_msi_free,
};

/**
 * hv_pcie_init_irq_domain() - Initialize IRQ domain
 * @hbus:       The root PCI bus
 *
 * This function creates an IRQ domain which will be used for
 * interrupts from devices that have been passed through.  These
 * devices only support MSI and MSI-X, not line-based interrupts
 * or simulations of line-based interrupts through PCIe's
 * fabric-layer messages.  Because interrupts are remapped, we
 * can support multi-message MSI here.
 *
 * Return: '0' on success and error value on failure
 */
static int hv_pcie_init_irq_domain(struct hv_pcibus_device *hbus)
{
        hbus->msi_info.chip = &hv_msi_irq_chip;
        hbus->msi_info.ops = &hv_msi_ops;
        hbus->msi_info.flags = (MSI_FLAG_USE_DEF_DOM_OPS |
                MSI_FLAG_USE_DEF_CHIP_OPS | MSI_FLAG_MULTI_PCI_MSI |
                MSI_FLAG_PCI_MSIX);
        hbus->msi_info.handler = handle_edge_irq;
        hbus->msi_info.handler_name = "edge";
        hbus->msi_info.data = hbus;
        hbus->irq_domain = pci_msi_create_irq_domain(hbus->sysdata.fwnode,
                                                     &hbus->msi_info,
                                                     x86_vector_domain);
        if (!hbus->irq_domain) {
                dev_err(&hbus->hdev->device,
                        "Failed to build an MSI IRQ domain\n");
                return -ENODEV;
        }

        return 0;
}

/**
 * get_bar_size() - Get the address space consumed by a BAR
 * @bar_val:    Value that a BAR returned after -1 was written
 *              to it.
 *
 * This function returns the size of the BAR, rounded up to 1
 * page.  It has to be rounded up because the hypervisor's page
 * table entry that maps the BAR into the VM can't specify an
 * offset within a page.  The invariant is that the hypervisor
 * must place any BARs of smaller than page length at the
 * beginning of a page.
 *
 * Return:      Size in bytes of the consumed MMIO space.
 */
static u64 get_bar_size(u64 bar_val)
{
        return round_up((1 + ~(bar_val & PCI_BASE_ADDRESS_MEM_MASK)),
                        PAGE_SIZE);
}

/**
 * survey_child_resources() - Total all MMIO requirements
 * @hbus:       Root PCI bus, as understood by this driver
 */
static void survey_child_resources(struct hv_pcibus_device *hbus)
{
        struct hv_pci_dev *hpdev;
        resource_size_t bar_size = 0;
        unsigned long flags;
        struct completion *event;
        u64 bar_val;
        int i;

        /* If nobody is waiting on the answer, don't compute it. */
        event = xchg(&hbus->survey_event, NULL);
        if (!event)
                return;

        /* If the answer has already been computed, go with it. */
        if (hbus->low_mmio_space || hbus->high_mmio_space) {
                complete(event);
                return;
        }

        spin_lock_irqsave(&hbus->device_list_lock, flags);

        /*
         * Due to an interesting quirk of the PCI spec, all memory regions
         * for a child device are a power of 2 in size and aligned in memory,
         * so it's sufficient to just add them up without tracking alignment.
         */
        list_for_each_entry(hpdev, &hbus->children, list_entry) {
                for (i = 0; i < PCI_STD_NUM_BARS; i++) {
                        if (hpdev->probed_bar[i] & PCI_BASE_ADDRESS_SPACE_IO)
                                dev_err(&hbus->hdev->device,
                                        "There's an I/O BAR in this list!\n");

                        if (hpdev->probed_bar[i] != 0) {
                                /*
                                 * A probed BAR has all the upper bits set that
                                 * can be changed.
                                 */

                                bar_val = hpdev->probed_bar[i];
                                if (bar_val & PCI_BASE_ADDRESS_MEM_TYPE_64)
                                        bar_val |=
                                        ((u64)hpdev->probed_bar[++i] << 32);
                                else
                                        bar_val |= 0xffffffff00000000ULL;

                                bar_size = get_bar_size(bar_val);

                                if (bar_val & PCI_BASE_ADDRESS_MEM_TYPE_64)
                                        hbus->high_mmio_space += bar_size;
                                else
                                        hbus->low_mmio_space += bar_size;
                        }
                }
        }

        spin_unlock_irqrestore(&hbus->device_list_lock, flags);
        complete(event);
}

/**
 * prepopulate_bars() - Fill in BARs with defaults
 * @hbus:       Root PCI bus, as understood by this driver
 *
 * The core PCI driver code seems much, much happier if the BARs
 * for a device have values upon first scan. So fill them in.
 * The algorithm below works down from large sizes to small,
 * attempting to pack the assignments optimally. The assumption,
 * enforced in other parts of the code, is that the beginning of
 * the memory-mapped I/O space will be aligned on the largest
 * BAR size.
 */
static void prepopulate_bars(struct hv_pcibus_device *hbus)
{
        resource_size_t high_size = 0;
        resource_size_t low_size = 0;
        resource_size_t high_base = 0;
        resource_size_t low_base = 0;
        resource_size_t bar_size;
        struct hv_pci_dev *hpdev;
        unsigned long flags;
        u64 bar_val;
        u32 command;
        bool high;
        int i;

        if (hbus->low_mmio_space) {
                low_size = 1ULL << (63 - __builtin_clzll(hbus->low_mmio_space));
                low_base = hbus->low_mmio_res->start;
        }

        if (hbus->high_mmio_space) {
                high_size = 1ULL <<
                        (63 - __builtin_clzll(hbus->high_mmio_space));
                high_base = hbus->high_mmio_res->start;
        }

        spin_lock_irqsave(&hbus->device_list_lock, flags);

        /*
         * Clear the memory enable bit, in case it's already set. This occurs
         * in the suspend path of hibernation, where the device is suspended,
         * resumed and suspended again: see hibernation_snapshot() and
         * hibernation_platform_enter().
         *
         * If the memory enable bit is already set, Hyper-V silently ignores
         * the below BAR updates, and the related PCI device driver can not
         * work, because reading from the device register(s) always returns
         * 0xFFFFFFFF.
         */
        list_for_each_entry(hpdev, &hbus->children, list_entry) {
                _hv_pcifront_read_config(hpdev, PCI_COMMAND, 2, &command);
                command &= ~PCI_COMMAND_MEMORY;
                _hv_pcifront_write_config(hpdev, PCI_COMMAND, 2, command);
        }

        /* Pick addresses for the BARs. */
        do {
                list_for_each_entry(hpdev, &hbus->children, list_entry) {
                        for (i = 0; i < PCI_STD_NUM_BARS; i++) {
                                bar_val = hpdev->probed_bar[i];
                                if (bar_val == 0)
                                        continue;
                                high = bar_val & PCI_BASE_ADDRESS_MEM_TYPE_64;
                                if (high) {
                                        bar_val |=
                                                ((u64)hpdev->probed_bar[i + 1]
                                                 << 32);
                                } else {
                                        bar_val |= 0xffffffffULL << 32;
                                }
                                bar_size = get_bar_size(bar_val);
                                if (high) {
                                        if (high_size != bar_size) {
                                                i++;
                                                continue;
                                        }
                                        _hv_pcifront_write_config(hpdev,
                                                PCI_BASE_ADDRESS_0 + (4 * i),
                                                4,
                                                (u32)(high_base & 0xffffff00));
                                        i++;
                                        _hv_pcifront_write_config(hpdev,
                                                PCI_BASE_ADDRESS_0 + (4 * i),
                                                4, (u32)(high_base >> 32));
                                        high_base += bar_size;
                                } else {
                                        if (low_size != bar_size)
                                                continue;
                                        _hv_pcifront_write_config(hpdev,
                                                PCI_BASE_ADDRESS_0 + (4 * i),
                                                4,
                                                (u32)(low_base & 0xffffff00));
                                        low_base += bar_size;
                                }
                        }
                        if (high_size <= 1 && low_size <= 1) {
                                /* Set the memory enable bit. */
                                _hv_pcifront_read_config(hpdev, PCI_COMMAND, 2,
                                                         &command);
                                command |= PCI_COMMAND_MEMORY;
                                _hv_pcifront_write_config(hpdev, PCI_COMMAND, 2,
                                                          command);
                                break;
                        }
                }

                high_size >>= 1;
                low_size >>= 1;
        }  while (high_size || low_size);

        spin_unlock_irqrestore(&hbus->device_list_lock, flags);
}

/*
 * Assign entries in sysfs pci slot directory.
 *
 * Note that this function does not need to lock the children list
 * because it is called from pci_devices_present_work which
 * is serialized with hv_eject_device_work because they are on the
 * same ordered workqueue. Therefore hbus->children list will not change
 * even when pci_create_slot sleeps.
 */
static void hv_pci_assign_slots(struct hv_pcibus_device *hbus)
{
        struct hv_pci_dev *hpdev;
        char name[SLOT_NAME_SIZE];
        int slot_nr;

        list_for_each_entry(hpdev, &hbus->children, list_entry) {
                if (hpdev->pci_slot)
                        continue;

                slot_nr = PCI_SLOT(wslot_to_devfn(hpdev->desc.win_slot.slot));
                snprintf(name, SLOT_NAME_SIZE, "%u", hpdev->desc.ser);
                hpdev->pci_slot = pci_create_slot(hbus->pci_bus, slot_nr,
                                          name, NULL);
                if (IS_ERR(hpdev->pci_slot)) {
                        pr_warn("pci_create slot %s failed\n", name);
                        hpdev->pci_slot = NULL;
                }
        }
}

/*
 * Remove entries in sysfs pci slot directory.
 */
static void hv_pci_remove_slots(struct hv_pcibus_device *hbus)
{
        struct hv_pci_dev *hpdev;

        list_for_each_entry(hpdev, &hbus->children, list_entry) {
                if (!hpdev->pci_slot)
                        continue;
                pci_destroy_slot(hpdev->pci_slot);
                hpdev->pci_slot = NULL;
        }
}

/*
 * Set NUMA node for the devices on the bus
 */
static void hv_pci_assign_numa_node(struct hv_pcibus_device *hbus)
{
        struct pci_dev *dev;
        struct pci_bus *bus = hbus->pci_bus;
        struct hv_pci_dev *hv_dev;

        list_for_each_entry(dev, &bus->devices, bus_list) {
                hv_dev = get_pcichild_wslot(hbus, devfn_to_wslot(dev->devfn));
                if (!hv_dev)
                        continue;

                if (hv_dev->desc.flags & HV_PCI_DEVICE_FLAG_NUMA_AFFINITY)
                        set_dev_node(&dev->dev, hv_dev->desc.virtual_numa_node);

                put_pcichild(hv_dev);
        }
}

/**
 * create_root_hv_pci_bus() - Expose a new root PCI bus
 * @hbus:       Root PCI bus, as understood by this driver
 *
 * Return: 0 on success, -errno on failure
 */
static int create_root_hv_pci_bus(struct hv_pcibus_device *hbus)
{
        /* Register the device */
        hbus->pci_bus = pci_create_root_bus(&hbus->hdev->device,
                                            0, /* bus number is always zero */
                                            &hv_pcifront_ops,
                                            &hbus->sysdata,
                                            &hbus->resources_for_children);
        if (!hbus->pci_bus)
                return -ENODEV;

        pci_lock_rescan_remove();
        pci_scan_child_bus(hbus->pci_bus);
        hv_pci_assign_numa_node(hbus);
        pci_bus_assign_resources(hbus->pci_bus);
        hv_pci_assign_slots(hbus);
        pci_bus_add_devices(hbus->pci_bus);
        pci_unlock_rescan_remove();
        hbus->state = hv_pcibus_installed;
        return 0;
}

struct q_res_req_compl {
        struct completion host_event;
        struct hv_pci_dev *hpdev;
};

/**
 * q_resource_requirements() - Query Resource Requirements
 * @context:            The completion context.
 * @resp:               The response that came from the host.
 * @resp_packet_size:   The size in bytes of resp.
 *
 * This function is invoked on completion of a Query Resource
 * Requirements packet.
 */
static void q_resource_requirements(void *context, struct pci_response *resp,
                                    int resp_packet_size)
{
        struct q_res_req_compl *completion = context;
        struct pci_q_res_req_response *q_res_req =
                (struct pci_q_res_req_response *)resp;
        int i;

        if (resp->status < 0) {
                dev_err(&completion->hpdev->hbus->hdev->device,
                        "query resource requirements failed: %x\n",
                        resp->status);
        } else {
                for (i = 0; i < PCI_STD_NUM_BARS; i++) {
                        completion->hpdev->probed_bar[i] =
                                q_res_req->probed_bar[i];
                }
        }

        complete(&completion->host_event);
}

/**
 * new_pcichild_device() - Create a new child device
 * @hbus:       The internal struct tracking this root PCI bus.
 * @desc:       The information supplied so far from the host
 *              about the device.
 *
 * This function creates the tracking structure for a new child
 * device and kicks off the process of figuring out what it is.
 *
 * Return: Pointer to the new tracking struct
 */
static struct hv_pci_dev *new_pcichild_device(struct hv_pcibus_device *hbus,
                struct hv_pcidev_description *desc)
{
        struct hv_pci_dev *hpdev;
        struct pci_child_message *res_req;
        struct q_res_req_compl comp_pkt;
        struct {
                struct pci_packet init_packet;
                u8 buffer[sizeof(struct pci_child_message)];
        } pkt;
        unsigned long flags;
        int ret;

        hpdev = kzalloc(sizeof(*hpdev), GFP_KERNEL);
        if (!hpdev)
                return NULL;

        hpdev->hbus = hbus;

        memset(&pkt, 0, sizeof(pkt));
        init_completion(&comp_pkt.host_event);
        comp_pkt.hpdev = hpdev;
        pkt.init_packet.compl_ctxt = &comp_pkt;
        pkt.init_packet.completion_func = q_resource_requirements;
        res_req = (struct pci_child_message *)&pkt.init_packet.message;
        res_req->message_type.type = PCI_QUERY_RESOURCE_REQUIREMENTS;
        res_req->wslot.slot = desc->win_slot.slot;

        ret = vmbus_sendpacket(hbus->hdev->channel, res_req,
                               sizeof(struct pci_child_message),
                               (unsigned long)&pkt.init_packet,
                               VM_PKT_DATA_INBAND,
                               VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED);
        if (ret)
                goto error;

        if (wait_for_response(hbus->hdev, &comp_pkt.host_event))
                goto error;

        hpdev->desc = *desc;
        refcount_set(&hpdev->refs, 1);
        get_pcichild(hpdev);
        spin_lock_irqsave(&hbus->device_list_lock, flags);

        list_add_tail(&hpdev->list_entry, &hbus->children);
        spin_unlock_irqrestore(&hbus->device_list_lock, flags);
        return hpdev;

error:
        kfree(hpdev);
        return NULL;
}

/**
 * get_pcichild_wslot() - Find device from slot
 * @hbus:       Root PCI bus, as understood by this driver
 * @wslot:      Location on the bus
 *
 * This function looks up a PCI device and returns the internal
 * representation of it.  It acquires a reference on it, so that
 * the device won't be deleted while somebody is using it.  The
 * caller is responsible for calling put_pcichild() to release
 * this reference.
 *
 * Return:      Internal representation of a PCI device
 */
static struct hv_pci_dev *get_pcichild_wslot(struct hv_pcibus_device *hbus,
                                             u32 wslot)
{
        unsigned long flags;
        struct hv_pci_dev *iter, *hpdev = NULL;

        spin_lock_irqsave(&hbus->device_list_lock, flags);
        list_for_each_entry(iter, &hbus->children, list_entry) {
                if (iter->desc.win_slot.slot == wslot) {
                        hpdev = iter;
                        get_pcichild(hpdev);
                        break;
                }
        }
        spin_unlock_irqrestore(&hbus->device_list_lock, flags);

        return hpdev;
}

/**
 * pci_devices_present_work() - Handle new list of child devices
 * @work:       Work struct embedded in struct hv_dr_work
 *
 * "Bus Relations" is the Windows term for "children of this
 * bus."  The terminology is preserved here for people trying to
 * debug the interaction between Hyper-V and Linux.  This
 * function is called when the parent partition reports a list
 * of functions that should be observed under this PCI Express
 * port (bus).
 *
 * This function updates the list, and must tolerate being
 * called multiple times with the same information.  The typical
 * number of child devices is one, with very atypical cases
 * involving three or four, so the algorithms used here can be
 * simple and inefficient.
 *
 * It must also treat the omission of a previously observed device as
 * notification that the device no longer exists.
 *
 * Note that this function is serialized with hv_eject_device_work(),
 * because both are pushed to the ordered workqueue hbus->wq.
 */
static void pci_devices_present_work(struct work_struct *work)
{
        u32 child_no;
        bool found;
        struct hv_pcidev_description *new_desc;
        struct hv_pci_dev *hpdev;
        struct hv_pcibus_device *hbus;
        struct list_head removed;
        struct hv_dr_work *dr_wrk;
        struct hv_dr_state *dr = NULL;
        unsigned long flags;

        dr_wrk = container_of(work, struct hv_dr_work, wrk);
        hbus = dr_wrk->bus;
        kfree(dr_wrk);

        INIT_LIST_HEAD(&removed);

        /* Pull this off the queue and process it if it was the last one. */
        spin_lock_irqsave(&hbus->device_list_lock, flags);
        while (!list_empty(&hbus->dr_list)) {
                dr = list_first_entry(&hbus->dr_list, struct hv_dr_state,
                                      list_entry);
                list_del(&dr->list_entry);

                /* Throw this away if the list still has stuff in it. */
                if (!list_empty(&hbus->dr_list)) {
                        kfree(dr);
                        continue;
                }
        }
        spin_unlock_irqrestore(&hbus->device_list_lock, flags);

        if (!dr)
                return;

        /* First, mark all existing children as reported missing. */
        spin_lock_irqsave(&hbus->device_list_lock, flags);
        list_for_each_entry(hpdev, &hbus->children, list_entry) {
                hpdev->reported_missing = true;
        }
        spin_unlock_irqrestore(&hbus->device_list_lock, flags);

        /* Next, add back any reported devices. */
        for (child_no = 0; child_no < dr->device_count; child_no++) {
                found = false;
                new_desc = &dr->func[child_no];

                spin_lock_irqsave(&hbus->device_list_lock, flags);
                list_for_each_entry(hpdev, &hbus->children, list_entry) {
                        if ((hpdev->desc.win_slot.slot == new_desc->win_slot.slot) &&
                            (hpdev->desc.v_id == new_desc->v_id) &&
                            (hpdev->desc.d_id == new_desc->d_id) &&
                            (hpdev->desc.ser == new_desc->ser)) {
                                hpdev->reported_missing = false;
                                found = true;
                        }
                }
                spin_unlock_irqrestore(&hbus->device_list_lock, flags);

                if (!found) {
                        hpdev = new_pcichild_device(hbus, new_desc);
                        if (!hpdev)
                                dev_err(&hbus->hdev->device,
                                        "couldn't record a child device.\n");
                }
        }

        /* Move missing children to a list on the stack. */
        spin_lock_irqsave(&hbus->device_list_lock, flags);
        do {
                found = false;
                list_for_each_entry(hpdev, &hbus->children, list_entry) {
                        if (hpdev->reported_missing) {
                                found = true;
                                put_pcichild(hpdev);
                                list_move_tail(&hpdev->list_entry, &removed);
                                break;
                        }
                }
        } while (found);
        spin_unlock_irqrestore(&hbus->device_list_lock, flags);

        /* Delete everything that should no longer exist. */
        while (!list_empty(&removed)) {
                hpdev = list_first_entry(&removed, struct hv_pci_dev,
                                         list_entry);
                list_del(&hpdev->list_entry);

                if (hpdev->pci_slot)
                        pci_destroy_slot(hpdev->pci_slot);

                put_pcichild(hpdev);
        }

        switch (hbus->state) {
        case hv_pcibus_installed:
                /*
                 * Tell the core to rescan bus
                 * because there may have been changes.
                 */
                pci_lock_rescan_remove();
                pci_scan_child_bus(hbus->pci_bus);
                hv_pci_assign_numa_node(hbus);
                hv_pci_assign_slots(hbus);
                pci_unlock_rescan_remove();
                break;

        case hv_pcibus_init:
        case hv_pcibus_probed:
                survey_child_resources(hbus);
                break;

        default:
                break;
        }

        kfree(dr);
}

/**
 * hv_pci_start_relations_work() - Queue work to start device discovery
 * @hbus:       Root PCI bus, as understood by this driver
 * @dr:         The list of children returned from host
 *
 * Return:  0 on success, -errno on failure
 */
static int hv_pci_start_relations_work(struct hv_pcibus_device *hbus,
                                       struct hv_dr_state *dr)
{
        struct hv_dr_work *dr_wrk;
        unsigned long flags;
        bool pending_dr;

        if (hbus->state == hv_pcibus_removing) {
                dev_info(&hbus->hdev->device,
                         "PCI VMBus BUS_RELATIONS: ignored\n");
                return -ENOENT;
        }

        dr_wrk = kzalloc(sizeof(*dr_wrk), GFP_NOWAIT);
        if (!dr_wrk)
                return -ENOMEM;

        INIT_WORK(&dr_wrk->wrk, pci_devices_present_work);
        dr_wrk->bus = hbus;

        spin_lock_irqsave(&hbus->device_list_lock, flags);
        /*
         * If pending_dr is true, we have already queued a work,
         * which will see the new dr. Otherwise, we need to
         * queue a new work.
         */
        pending_dr = !list_empty(&hbus->dr_list);
        list_add_tail(&dr->list_entry, &hbus->dr_list);
        spin_unlock_irqrestore(&hbus->device_list_lock, flags);

        if (pending_dr)
                kfree(dr_wrk);
        else
                queue_work(hbus->wq, &dr_wrk->wrk);

        return 0;
}

/**
 * hv_pci_devices_present() - Handle list of new children
 * @hbus:      Root PCI bus, as understood by this driver
 * @relations: Packet from host listing children
 *
 * Process a new list of devices on the bus. The list of devices is
 * discovered by VSP and sent to us via VSP message PCI_BUS_RELATIONS,
 * whenever a new list of devices for this bus appears.
 */
static void hv_pci_devices_present(struct hv_pcibus_device *hbus,
                                   struct pci_bus_relations *relations)
{
        struct hv_dr_state *dr;
        int i;

        dr = kzalloc(struct_size(dr, func, relations->device_count),
                     GFP_NOWAIT);
        if (!dr)
                return;

        dr->device_count = relations->device_count;
        for (i = 0; i < dr->device_count; i++) {
                dr->func[i].v_id = relations->func[i].v_id;
                dr->func[i].d_id = relations->func[i].d_id;
                dr->func[i].rev = relations->func[i].rev;
                dr->func[i].prog_intf = relations->func[i].prog_intf;
                dr->func[i].subclass = relations->func[i].subclass;
                dr->func[i].base_class = relations->func[i].base_class;
                dr->func[i].subsystem_id = relations->func[i].subsystem_id;
                dr->func[i].win_slot = relations->func[i].win_slot;
                dr->func[i].ser = relations->func[i].ser;
        }

        if (hv_pci_start_relations_work(hbus, dr))
                kfree(dr);
}

/**
 * hv_pci_devices_present2() - Handle list of new children
 * @hbus:       Root PCI bus, as understood by this driver
 * @relations:  Packet from host listing children
 *
 * This function is the v2 version of hv_pci_devices_present()
 */
static void hv_pci_devices_present2(struct hv_pcibus_device *hbus,
                                    struct pci_bus_relations2 *relations)
{
        struct hv_dr_state *dr;
        int i;

        dr = kzalloc(struct_size(dr, func, relations->device_count),
                     GFP_NOWAIT);
        if (!dr)
                return;

        dr->device_count = relations->device_count;
        for (i = 0; i < dr->device_count; i++) {
                dr->func[i].v_id = relations->func[i].v_id;
                dr->func[i].d_id = relations->func[i].d_id;
                dr->func[i].rev = relations->func[i].rev;
                dr->func[i].prog_intf = relations->func[i].prog_intf;
                dr->func[i].subclass = relations->func[i].subclass;
                dr->func[i].base_class = relations->func[i].base_class;
                dr->func[i].subsystem_id = relations->func[i].subsystem_id;
                dr->func[i].win_slot = relations->func[i].win_slot;
                dr->func[i].ser = relations->func[i].ser;
                dr->func[i].flags = relations->func[i].flags;
                dr->func[i].virtual_numa_node =
                        relations->func[i].virtual_numa_node;
        }

        if (hv_pci_start_relations_work(hbus, dr))
                kfree(dr);
}

/**
 * hv_eject_device_work() - Asynchronously handles ejection
 * @work:       Work struct embedded in internal device struct
 *
 * This function handles ejecting a device.  Windows will
 * attempt to gracefully eject a device, waiting 60 seconds to
 * hear back from the guest OS that this completed successfully.
 * If this timer expires, the device will be forcibly removed.
 */
static void hv_eject_device_work(struct work_struct *work)
{
        struct pci_eject_response *ejct_pkt;
        struct hv_pcibus_device *hbus;
        struct hv_pci_dev *hpdev;
        struct pci_dev *pdev;
        unsigned long flags;
        int wslot;
        struct {
                struct pci_packet pkt;
                u8 buffer[sizeof(struct pci_eject_response)];
        } ctxt;

        hpdev = container_of(work, struct hv_pci_dev, wrk);
        hbus = hpdev->hbus;

        WARN_ON(hpdev->state != hv_pcichild_ejecting);

        /*
         * Ejection can come before or after the PCI bus has been set up, so
         * attempt to find it and tear down the bus state, if it exists.  This
         * must be done without constructs like pci_domain_nr(hbus->pci_bus)
         * because hbus->pci_bus may not exist yet.
         */
        wslot = wslot_to_devfn(hpdev->desc.win_slot.slot);
        pdev = pci_get_domain_bus_and_slot(hbus->sysdata.domain, 0, wslot);
        if (pdev) {
                pci_lock_rescan_remove();
                pci_stop_and_remove_bus_device(pdev);
                pci_dev_put(pdev);
                pci_unlock_rescan_remove();
        }

        spin_lock_irqsave(&hbus->device_list_lock, flags);
        list_del(&hpdev->list_entry);
        spin_unlock_irqrestore(&hbus->device_list_lock, flags);

        if (hpdev->pci_slot)
                pci_destroy_slot(hpdev->pci_slot);

        memset(&ctxt, 0, sizeof(ctxt));
        ejct_pkt = (struct pci_eject_response *)&ctxt.pkt.message;
        ejct_pkt->message_type.type = PCI_EJECTION_COMPLETE;
        ejct_pkt->wslot.slot = hpdev->desc.win_slot.slot;
        vmbus_sendpacket(hbus->hdev->channel, ejct_pkt,
                         sizeof(*ejct_pkt), (unsigned long)&ctxt.pkt,
                         VM_PKT_DATA_INBAND, 0);

        /* For the get_pcichild() in hv_pci_eject_device() */
        put_pcichild(hpdev);
        /* For the two refs got in new_pcichild_device() */
        put_pcichild(hpdev);
        put_pcichild(hpdev);
        /* hpdev has been freed. Do not use it any more. */
}

/**
 * hv_pci_eject_device() - Handles device ejection
 * @hpdev:      Internal device tracking struct
 *
 * This function is invoked when an ejection packet arrives.  It
 * just schedules work so that we don't re-enter the packet
 * delivery code handling the ejection.
 */
static void hv_pci_eject_device(struct hv_pci_dev *hpdev)
{
        struct hv_pcibus_device *hbus = hpdev->hbus;
        struct hv_device *hdev = hbus->hdev;

        if (hbus->state == hv_pcibus_removing) {
                dev_info(&hdev->device, "PCI VMBus EJECT: ignored\n");
                return;
        }

        hpdev->state = hv_pcichild_ejecting;
        get_pcichild(hpdev);
        INIT_WORK(&hpdev->wrk, hv_eject_device_work);
        queue_work(hbus->wq, &hpdev->wrk);
}

/**
 * hv_pci_onchannelcallback() - Handles incoming packets
 * @context:    Internal bus tracking struct
 *
 * This function is invoked whenever the host sends a packet to
 * this channel (which is private to this root PCI bus).
 */
static void hv_pci_onchannelcallback(void *context)
{
        const int packet_size = 0x100;
        int ret;
        struct hv_pcibus_device *hbus = context;
        u32 bytes_recvd;
        u64 req_id;
        struct vmpacket_descriptor *desc;
        unsigned char *buffer;
        int bufferlen = packet_size;
        struct pci_packet *comp_packet;
        struct pci_response *response;
        struct pci_incoming_message *new_message;
        struct pci_bus_relations *bus_rel;
        struct pci_bus_relations2 *bus_rel2;
        struct pci_dev_inval_block *inval;
        struct pci_dev_incoming *dev_message;
        struct hv_pci_dev *hpdev;

        buffer = kmalloc(bufferlen, GFP_ATOMIC);
        if (!buffer)
                return;

        while (1) {
                ret = vmbus_recvpacket_raw(hbus->hdev->channel, buffer,
                                           bufferlen, &bytes_recvd, &req_id);

                if (ret == -ENOBUFS) {
                        kfree(buffer);
                        /* Handle large packet */
                        bufferlen = bytes_recvd;
                        buffer = kmalloc(bytes_recvd, GFP_ATOMIC);
                        if (!buffer)
                                return;
                        continue;
                }

                /* Zero length indicates there are no more packets. */
                if (ret || !bytes_recvd)
                        break;

                /*
                 * All incoming packets must be at least as large as a
                 * response.
                 */
                if (bytes_recvd <= sizeof(struct pci_response))
                        continue;
                desc = (struct vmpacket_descriptor *)buffer;

                switch (desc->type) {
                case VM_PKT_COMP:

                        /*
                         * The host is trusted, and thus it's safe to interpret
                         * this transaction ID as a pointer.
                         */
                        comp_packet = (struct pci_packet *)req_id;
                        response = (struct pci_response *)buffer;
                        comp_packet->completion_func(comp_packet->compl_ctxt,
                                                     response,
                                                     bytes_recvd);
                        break;

                case VM_PKT_DATA_INBAND:

                        new_message = (struct pci_incoming_message *)buffer;
                        switch (new_message->message_type.type) {
                        case PCI_BUS_RELATIONS:

                                bus_rel = (struct pci_bus_relations *)buffer;
                                if (bytes_recvd <
                                        struct_size(bus_rel, func,
                                                    bus_rel->device_count)) {
                                        dev_err(&hbus->hdev->device,
                                                "bus relations too small\n");
                                        break;
                                }

                                hv_pci_devices_present(hbus, bus_rel);
                                break;

                        case PCI_BUS_RELATIONS2:

                                bus_rel2 = (struct pci_bus_relations2 *)buffer;
                                if (bytes_recvd <
                                        struct_size(bus_rel2, func,
                                                    bus_rel2->device_count)) {
                                        dev_err(&hbus->hdev->device,
                                                "bus relations v2 too small\n");
                                        break;
                                }

                                hv_pci_devices_present2(hbus, bus_rel2);
                                break;

                        case PCI_EJECT:

                                dev_message = (struct pci_dev_incoming *)buffer;
                                hpdev = get_pcichild_wslot(hbus,
                                                      dev_message->wslot.slot);
                                if (hpdev) {
                                        hv_pci_eject_device(hpdev);
                                        put_pcichild(hpdev);
                                }
                                break;

                        case PCI_INVALIDATE_BLOCK:

                                inval = (struct pci_dev_inval_block *)buffer;
                                hpdev = get_pcichild_wslot(hbus,
                                                           inval->wslot.slot);
                                if (hpdev) {
                                        if (hpdev->block_invalidate) {
                                                hpdev->block_invalidate(
                                                    hpdev->invalidate_context,
                                                    inval->block_mask);
                                        }
                                        put_pcichild(hpdev);
                                }
                                break;

                        default:
                                dev_warn(&hbus->hdev->device,
                                        "Unimplemented protocol message %x\n",
                                        new_message->message_type.type);
                                break;
                        }
                        break;

                default:
                        dev_err(&hbus->hdev->device,
                                "unhandled packet type %d, tid %llx len %d\n",
                                desc->type, req_id, bytes_recvd);
                        break;
                }
        }

        kfree(buffer);
}

/**
 * hv_pci_protocol_negotiation() - Set up protocol
 * @hdev:               VMBus's tracking struct for this root PCI bus.
 * @version:            Array of supported channel protocol versions in
 *                      the order of probing - highest go first.
 * @num_version:        Number of elements in the version array.
 *
 * This driver is intended to support running on Windows 10
 * (server) and later versions. It will not run on earlier
 * versions, as they assume that many of the operations which
 * Linux needs accomplished with a spinlock held were done via
 * asynchronous messaging via VMBus.  Windows 10 increases the
 * surface area of PCI emulation so that these actions can take
 * place by suspending a virtual processor for their duration.
 *
 * This function negotiates the channel protocol version,
 * failing if the host doesn't support the necessary protocol
 * level.
 */
static int hv_pci_protocol_negotiation(struct hv_device *hdev,
                                       enum pci_protocol_version_t version[],
                                       int num_version)
{
        struct hv_pcibus_device *hbus = hv_get_drvdata(hdev);
        struct pci_version_request *version_req;
        struct hv_pci_compl comp_pkt;
        struct pci_packet *pkt;
        int ret;
        int i;

        /*
         * Initiate the handshake with the host and negotiate
         * a version that the host can support. We start with the
         * highest version number and go down if the host cannot
         * support it.
         */
        pkt = kzalloc(sizeof(*pkt) + sizeof(*version_req), GFP_KERNEL);
        if (!pkt)
                return -ENOMEM;

        init_completion(&comp_pkt.host_event);
        pkt->completion_func = hv_pci_generic_compl;
        pkt->compl_ctxt = &comp_pkt;
        version_req = (struct pci_version_request *)&pkt->message;
        version_req->message_type.type = PCI_QUERY_PROTOCOL_VERSION;

        for (i = 0; i < num_version; i++) {
                version_req->protocol_version = version[i];
                ret = vmbus_sendpacket(hdev->channel, version_req,
                                sizeof(struct pci_version_request),
                                (unsigned long)pkt, VM_PKT_DATA_INBAND,
                                VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED);
                if (!ret)
                        ret = wait_for_response(hdev, &comp_pkt.host_event);

                if (ret) {
                        dev_err(&hdev->device,
                                "PCI Pass-through VSP failed to request version: %d",
                                ret);
                        goto exit;
                }

                if (comp_pkt.completion_status >= 0) {
                        hbus->protocol_version = version[i];
                        dev_info(&hdev->device,
                                "PCI VMBus probing: Using version %#x\n",
                                hbus->protocol_version);
                        goto exit;
                }

                if (comp_pkt.completion_status != STATUS_REVISION_MISMATCH) {
                        dev_err(&hdev->device,
                                "PCI Pass-through VSP failed version request: %#x",
                                comp_pkt.completion_status);
                        ret = -EPROTO;
                        goto exit;
                }

                reinit_completion(&comp_pkt.host_event);
        }

        dev_err(&hdev->device,
                "PCI pass-through VSP failed to find supported version");
        ret = -EPROTO;

exit:
        kfree(pkt);
        return ret;
}

/**
 * hv_pci_free_bridge_windows() - Release memory regions for the
 * bus
 * @hbus:       Root PCI bus, as understood by this driver
 */
static void hv_pci_free_bridge_windows(struct hv_pcibus_device *hbus)
{
        /*
         * Set the resources back to the way they looked when they
         * were allocated by setting IORESOURCE_BUSY again.
         */

        if (hbus->low_mmio_space && hbus->low_mmio_res) {
                hbus->low_mmio_res->flags |= IORESOURCE_BUSY;
                vmbus_free_mmio(hbus->low_mmio_res->start,
                                resource_size(hbus->low_mmio_res));
        }

        if (hbus->high_mmio_space && hbus->high_mmio_res) {
                hbus->high_mmio_res->flags |= IORESOURCE_BUSY;
                vmbus_free_mmio(hbus->high_mmio_res->start,
                                resource_size(hbus->high_mmio_res));
        }
}

/**
 * hv_pci_allocate_bridge_windows() - Allocate memory regions
 * for the bus
 * @hbus:       Root PCI bus, as understood by this driver
 *
 * This function calls vmbus_allocate_mmio(), which is itself a
 * bit of a compromise.  Ideally, we might change the pnp layer
 * in the kernel such that it comprehends either PCI devices
 * which are "grandchildren of ACPI," with some intermediate bus
 * node (in this case, VMBus) or change it such that it
 * understands VMBus.  The pnp layer, however, has been declared
 * deprecated, and not subject to change.
 *
 * The workaround, implemented here, is to ask VMBus to allocate
 * MMIO space for this bus.  VMBus itself knows which ranges are
 * appropriate by looking at its own ACPI objects.  Then, after
 * these ranges are claimed, they're modified to look like they
 * would have looked if the ACPI and pnp code had allocated
 * bridge windows.  These descriptors have to exist in this form
 * in order to satisfy the code which will get invoked when the
 * endpoint PCI function driver calls request_mem_region() or
 * request_mem_region_exclusive().
 *
 * Return: 0 on success, -errno on failure
 */
static int hv_pci_allocate_bridge_windows(struct hv_pcibus_device *hbus)
{
        resource_size_t align;
        int ret;

        if (hbus->low_mmio_space) {
                align = 1ULL << (63 - __builtin_clzll(hbus->low_mmio_space));
                ret = vmbus_allocate_mmio(&hbus->low_mmio_res, hbus->hdev, 0,
                                          (u64)(u32)0xffffffff,
                                          hbus->low_mmio_space,
                                          align, false);
                if (ret) {
                        dev_err(&hbus->hdev->device,
                                "Need %#llx of low MMIO space. Consider reconfiguring the VM.\n",
                                hbus->low_mmio_space);
                        return ret;
                }

                /* Modify this resource to become a bridge window. */
                hbus->low_mmio_res->flags |= IORESOURCE_WINDOW;
                hbus->low_mmio_res->flags &= ~IORESOURCE_BUSY;
                pci_add_resource(&hbus->resources_for_children,
                                 hbus->low_mmio_res);
        }

        if (hbus->high_mmio_space) {
                align = 1ULL << (63 - __builtin_clzll(hbus->high_mmio_space));
                ret = vmbus_allocate_mmio(&hbus->high_mmio_res, hbus->hdev,
                                          0x100000000, -1,
                                          hbus->high_mmio_space, align,
                                          false);
                if (ret) {
                        dev_err(&hbus->hdev->device,
                                "Need %#llx of high MMIO space. Consider reconfiguring the VM.\n",
                                hbus->high_mmio_space);
                        goto release_low_mmio;
                }

                /* Modify this resource to become a bridge window. */
                hbus->high_mmio_res->flags |= IORESOURCE_WINDOW;
                hbus->high_mmio_res->flags &= ~IORESOURCE_BUSY;
                pci_add_resource(&hbus->resources_for_children,
                                 hbus->high_mmio_res);
        }

        return 0;

release_low_mmio:
        if (hbus->low_mmio_res) {
                vmbus_free_mmio(hbus->low_mmio_res->start,
                                resource_size(hbus->low_mmio_res));
        }

        return ret;
}

/**
 * hv_allocate_config_window() - Find MMIO space for PCI Config
 * @hbus:       Root PCI bus, as understood by this driver
 *
 * This function claims memory-mapped I/O space for accessing
 * configuration space for the functions on this bus.
 *
 * Return: 0 on success, -errno on failure
 */
static int hv_allocate_config_window(struct hv_pcibus_device *hbus)
{
        int ret;

        /*
         * Set up a region of MMIO space to use for accessing configuration
         * space.
         */
        ret = vmbus_allocate_mmio(&hbus->mem_config, hbus->hdev, 0, -1,
                                  PCI_CONFIG_MMIO_LENGTH, 0x1000, false);
        if (ret)
                return ret;

        /*
         * vmbus_allocate_mmio() gets used for allocating both device endpoint
         * resource claims (those which cannot be overlapped) and the ranges
         * which are valid for the children of this bus, which are intended
         * to be overlapped by those children.  Set the flag on this claim
         * meaning that this region can't be overlapped.
         */

        hbus->mem_config->flags |= IORESOURCE_BUSY;

        return 0;
}

static void hv_free_config_window(struct hv_pcibus_device *hbus)
{
        vmbus_free_mmio(hbus->mem_config->start, PCI_CONFIG_MMIO_LENGTH);
}

static int hv_pci_bus_exit(struct hv_device *hdev, bool keep_devs);

/**
 * hv_pci_enter_d0() - Bring the "bus" into the D0 power state
 * @hdev:       VMBus's tracking struct for this root PCI bus
 *
 * Return: 0 on success, -errno on failure
 */
static int hv_pci_enter_d0(struct hv_device *hdev)
{
        struct hv_pcibus_device *hbus = hv_get_drvdata(hdev);
        struct pci_bus_d0_entry *d0_entry;
        struct hv_pci_compl comp_pkt;
        struct pci_packet *pkt;
        int ret;

        /*
         * Tell the host that the bus is ready to use, and moved into the
         * powered-on state.  This includes telling the host which region
         * of memory-mapped I/O space has been chosen for configuration space
         * access.
         */
        pkt = kzalloc(sizeof(*pkt) + sizeof(*d0_entry), GFP_KERNEL);
        if (!pkt)
                return -ENOMEM;

        init_completion(&comp_pkt.host_event);
        pkt->completion_func = hv_pci_generic_compl;
        pkt->compl_ctxt = &comp_pkt;
        d0_entry = (struct pci_bus_d0_entry *)&pkt->message;
        d0_entry->message_type.type = PCI_BUS_D0ENTRY;
        d0_entry->mmio_base = hbus->mem_config->start;

        ret = vmbus_sendpacket(hdev->channel, d0_entry, sizeof(*d0_entry),
                               (unsigned long)pkt, VM_PKT_DATA_INBAND,
                               VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED);
        if (!ret)
                ret = wait_for_response(hdev, &comp_pkt.host_event);

        if (ret)
                goto exit;

        if (comp_pkt.completion_status < 0) {
                dev_err(&hdev->device,
                        "PCI Pass-through VSP failed D0 Entry with status %x\n",
                        comp_pkt.completion_status);
                ret = -EPROTO;
                goto exit;
        }

        ret = 0;

exit:
        kfree(pkt);
        return ret;
}

/**
 * hv_pci_query_relations() - Ask host to send list of child
 * devices
 * @hdev:       VMBus's tracking struct for this root PCI bus
 *
 * Return: 0 on success, -errno on failure
 */
static int hv_pci_query_relations(struct hv_device *hdev)
{
        struct hv_pcibus_device *hbus = hv_get_drvdata(hdev);
        struct pci_message message;
        struct completion comp;
        int ret;

        /* Ask the host to send along the list of child devices */
        init_completion(&comp);
        if (cmpxchg(&hbus->survey_event, NULL, &comp))
                return -ENOTEMPTY;

        memset(&message, 0, sizeof(message));
        message.type = PCI_QUERY_BUS_RELATIONS;

        ret = vmbus_sendpacket(hdev->channel, &message, sizeof(message),
                               0, VM_PKT_DATA_INBAND, 0);
        if (!ret)
                ret = wait_for_response(hdev, &comp);

        return ret;
}

/**
 * hv_send_resources_allocated() - Report local resource choices
 * @hdev:       VMBus's tracking struct for this root PCI bus
 *
 * The host OS is expecting to be sent a request as a message
 * which contains all the resources that the device will use.
 * The response contains those same resources, "translated"
 * which is to say, the values which should be used by the
 * hardware, when it delivers an interrupt.  (MMIO resources are
 * used in local terms.)  This is nice for Windows, and lines up
 * with the FDO/PDO split, which doesn't exist in Linux.  Linux
 * is deeply expecting to scan an emulated PCI configuration
 * space.  So this message is sent here only to drive the state
 * machine on the host forward.
 *
 * Return: 0 on success, -errno on failure
 */
static int hv_send_resources_allocated(struct hv_device *hdev)
{
        struct hv_pcibus_device *hbus = hv_get_drvdata(hdev);
        struct pci_resources_assigned *res_assigned;
        struct pci_resources_assigned2 *res_assigned2;
        struct hv_pci_compl comp_pkt;
        struct hv_pci_dev *hpdev;
        struct pci_packet *pkt;
        size_t size_res;
        int wslot;
        int ret;

        size_res = (hbus->protocol_version < PCI_PROTOCOL_VERSION_1_2)
                        ? sizeof(*res_assigned) : sizeof(*res_assigned2);

        pkt = kmalloc(sizeof(*pkt) + size_res, GFP_KERNEL);
        if (!pkt)
                return -ENOMEM;

        ret = 0;

        for (wslot = 0; wslot < 256; wslot++) {
                hpdev = get_pcichild_wslot(hbus, wslot);
                if (!hpdev)
                        continue;

                memset(pkt, 0, sizeof(*pkt) + size_res);
                init_completion(&comp_pkt.host_event);
                pkt->completion_func = hv_pci_generic_compl;
                pkt->compl_ctxt = &comp_pkt;

                if (hbus->protocol_version < PCI_PROTOCOL_VERSION_1_2) {
                        res_assigned =
                                (struct pci_resources_assigned *)&pkt->message;
                        res_assigned->message_type.type =
                                PCI_RESOURCES_ASSIGNED;
                        res_assigned->wslot.slot = hpdev->desc.win_slot.slot;
                } else {
                        res_assigned2 =
                                (struct pci_resources_assigned2 *)&pkt->message;
                        res_assigned2->message_type.type =
                                PCI_RESOURCES_ASSIGNED2;
                        res_assigned2->wslot.slot = hpdev->desc.win_slot.slot;
                }
                put_pcichild(hpdev);

                ret = vmbus_sendpacket(hdev->channel, &pkt->message,
                                size_res, (unsigned long)pkt,
                                VM_PKT_DATA_INBAND,
                                VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED);
                if (!ret)
                        ret = wait_for_response(hdev, &comp_pkt.host_event);
                if (ret)
                        break;

                if (comp_pkt.completion_status < 0) {
                        ret = -EPROTO;
                        dev_err(&hdev->device,
                                "resource allocated returned 0x%x",
                                comp_pkt.completion_status);
                        break;
                }

                hbus->wslot_res_allocated = wslot;
        }

        kfree(pkt);
        return ret;
}

/**
 * hv_send_resources_released() - Report local resources
 * released
 * @hdev:       VMBus's tracking struct for this root PCI bus
 *
 * Return: 0 on success, -errno on failure
 */
static int hv_send_resources_released(struct hv_device *hdev)
{
        struct hv_pcibus_device *hbus = hv_get_drvdata(hdev);
        struct pci_child_message pkt;
        struct hv_pci_dev *hpdev;
        int wslot;
        int ret;

        for (wslot = hbus->wslot_res_allocated; wslot >= 0; wslot--) {
                hpdev = get_pcichild_wslot(hbus, wslot);
                if (!hpdev)
                        continue;

                memset(&pkt, 0, sizeof(pkt));
                pkt.message_type.type = PCI_RESOURCES_RELEASED;
                pkt.wslot.slot = hpdev->desc.win_slot.slot;

                put_pcichild(hpdev);

                ret = vmbus_sendpacket(hdev->channel, &pkt, sizeof(pkt), 0,
                                       VM_PKT_DATA_INBAND, 0);
                if (ret)
                        return ret;

                hbus->wslot_res_allocated = wslot - 1;
        }

        hbus->wslot_res_allocated = -1;

        return 0;
}

#define HVPCI_DOM_MAP_SIZE (64 * 1024)
static DECLARE_BITMAP(hvpci_dom_map, HVPCI_DOM_MAP_SIZE);

/*
 * PCI domain number 0 is used by emulated devices on Gen1 VMs, so define 0
 * as invalid for passthrough PCI devices of this driver.
 */
#define HVPCI_DOM_INVALID 0

/**
 * hv_get_dom_num() - Get a valid PCI domain number
 * Check if the PCI domain number is in use, and return another number if
 * it is in use.
 *
 * @dom: Requested domain number
 *
 * return: domain number on success, HVPCI_DOM_INVALID on failure
 */
static u16 hv_get_dom_num(u16 dom)
{
        unsigned int i;

        if (test_and_set_bit(dom, hvpci_dom_map) == 0)
                return dom;

        for_each_clear_bit(i, hvpci_dom_map, HVPCI_DOM_MAP_SIZE) {
                if (test_and_set_bit(i, hvpci_dom_map) == 0)
                        return i;
        }

        return HVPCI_DOM_INVALID;
}

/**
 * hv_put_dom_num() - Mark the PCI domain number as free
 * @dom: Domain number to be freed
 */
static void hv_put_dom_num(u16 dom)
{
        clear_bit(dom, hvpci_dom_map);
}

/**
 * hv_pci_probe() - New VMBus channel probe, for a root PCI bus
 * @hdev:       VMBus's tracking struct for this root PCI bus
 * @dev_id:     Identifies the device itself
 *
 * Return: 0 on success, -errno on failure
 */
static int hv_pci_probe(struct hv_device *hdev,
                        const struct hv_vmbus_device_id *dev_id)
{
        struct hv_pcibus_device *hbus;
        u16 dom_req, dom;
        char *name;
        bool enter_d0_retry = true;
        int ret;

        /*
         * hv_pcibus_device contains the hypercall arguments for retargeting in
         * hv_irq_unmask(). Those must not cross a page boundary.
         */
        BUILD_BUG_ON(sizeof(*hbus) > HV_HYP_PAGE_SIZE);

        /*
         * With the recent 59bb47985c1d ("mm, sl[aou]b: guarantee natural
         * alignment for kmalloc(power-of-two)"), kzalloc() is able to allocate
         * a 4KB buffer that is guaranteed to be 4KB-aligned. Here the size and
         * alignment of hbus is important because hbus's field
         * retarget_msi_interrupt_params must not cross a 4KB page boundary.
         *
         * Here we prefer kzalloc to get_zeroed_page(), because a buffer
         * allocated by the latter is not tracked and scanned by kmemleak, and
         * hence kmemleak reports the pointer contained in the hbus buffer
         * (i.e. the hpdev struct, which is created in new_pcichild_device() and
         * is tracked by hbus->children) as memory leak (false positive).
         *
         * If the kernel doesn't have 59bb47985c1d, get_zeroed_page() *must* be
         * used to allocate the hbus buffer and we can avoid the kmemleak false
         * positive by using kmemleak_alloc() and kmemleak_free() to ask
         * kmemleak to track and scan the hbus buffer.
         */
        hbus = kzalloc(HV_HYP_PAGE_SIZE, GFP_KERNEL);
        if (!hbus)
                return -ENOMEM;
        hbus->state = hv_pcibus_init;
        hbus->wslot_res_allocated = -1;

        /*
         * The PCI bus "domain" is what is called "segment" in ACPI and other
         * specs. Pull it from the instance ID, to get something usually
         * unique. In rare cases of collision, we will find out another number
         * not in use.
         *
         * Note that, since this code only runs in a Hyper-V VM, Hyper-V
         * together with this guest driver can guarantee that (1) The only
         * domain used by Gen1 VMs for something that looks like a physical
         * PCI bus (which is actually emulated by the hypervisor) is domain 0.
         * (2) There will be no overlap between domains (after fixing possible
         * collisions) in the same VM.
         */
        dom_req = hdev->dev_instance.b[5] << 8 | hdev->dev_instance.b[4];
        dom = hv_get_dom_num(dom_req);

        if (dom == HVPCI_DOM_INVALID) {
                dev_err(&hdev->device,
                        "Unable to use dom# 0x%hx or other numbers", dom_req);
                ret = -EINVAL;
                goto free_bus;
        }

        if (dom != dom_req)
                dev_info(&hdev->device,
                         "PCI dom# 0x%hx has collision, using 0x%hx",
                         dom_req, dom);

        hbus->sysdata.domain = dom;

        hbus->hdev = hdev;
        INIT_LIST_HEAD(&hbus->children);
        INIT_LIST_HEAD(&hbus->dr_list);
        INIT_LIST_HEAD(&hbus->resources_for_children);
        spin_lock_init(&hbus->config_lock);
        spin_lock_init(&hbus->device_list_lock);
        spin_lock_init(&hbus->retarget_msi_interrupt_lock);
        hbus->wq = alloc_ordered_workqueue("hv_pci_%x", 0,
                                           hbus->sysdata.domain);
        if (!hbus->wq) {
                ret = -ENOMEM;
                goto free_dom;
        }

        ret = vmbus_open(hdev->channel, pci_ring_size, pci_ring_size, NULL, 0,
                         hv_pci_onchannelcallback, hbus);
        if (ret)
                goto destroy_wq;

        hv_set_drvdata(hdev, hbus);

        ret = hv_pci_protocol_negotiation(hdev, pci_protocol_versions,
                                          ARRAY_SIZE(pci_protocol_versions));
        if (ret)
                goto close;

        ret = hv_allocate_config_window(hbus);
        if (ret)
                goto close;

        hbus->cfg_addr = ioremap(hbus->mem_config->start,
                                 PCI_CONFIG_MMIO_LENGTH);
        if (!hbus->cfg_addr) {
                dev_err(&hdev->device,
                        "Unable to map a virtual address for config space\n");
                ret = -ENOMEM;
                goto free_config;
        }

        name = kasprintf(GFP_KERNEL, "%pUL", &hdev->dev_instance);
        if (!name) {
                ret = -ENOMEM;
                goto unmap;
        }

        hbus->sysdata.fwnode = irq_domain_alloc_named_fwnode(name);
        kfree(name);
        if (!hbus->sysdata.fwnode) {
                ret = -ENOMEM;
                goto unmap;
        }

        ret = hv_pcie_init_irq_domain(hbus);
        if (ret)
                goto free_fwnode;

retry:
        ret = hv_pci_query_relations(hdev);
        if (ret)
                goto free_irq_domain;

        ret = hv_pci_enter_d0(hdev);
        /*
         * In certain case (Kdump) the pci device of interest was
         * not cleanly shut down and resource is still held on host
         * side, the host could return invalid device status.
         * We need to explicitly request host to release the resource
         * and try to enter D0 again.
         * Since the hv_pci_bus_exit() call releases structures
         * of all its child devices, we need to start the retry from
         * hv_pci_query_relations() call, requesting host to send
         * the synchronous child device relations message before this
         * information is needed in hv_send_resources_allocated()
         * call later.
         */
        if (ret == -EPROTO && enter_d0_retry) {
                enter_d0_retry = false;

                dev_err(&hdev->device, "Retrying D0 Entry\n");

                /*
                 * Hv_pci_bus_exit() calls hv_send_resources_released()
                 * to free up resources of its child devices.
                 * In the kdump kernel we need to set the
                 * wslot_res_allocated to 255 so it scans all child
                 * devices to release resources allocated in the
                 * normal kernel before panic happened.
                 */
                hbus->wslot_res_allocated = 255;
                ret = hv_pci_bus_exit(hdev, true);

                if (ret == 0)
                        goto retry;

                dev_err(&hdev->device,
                        "Retrying D0 failed with ret %d\n", ret);
        }
        if (ret)
                goto free_irq_domain;

        ret = hv_pci_allocate_bridge_windows(hbus);
        if (ret)
                goto exit_d0;

        ret = hv_send_resources_allocated(hdev);
        if (ret)
                goto free_windows;

        prepopulate_bars(hbus);

        hbus->state = hv_pcibus_probed;

        ret = create_root_hv_pci_bus(hbus);
        if (ret)
                goto free_windows;

        return 0;

free_windows:
        hv_pci_free_bridge_windows(hbus);
exit_d0:
        (void) hv_pci_bus_exit(hdev, true);
free_irq_domain:
        irq_domain_remove(hbus->irq_domain);
free_fwnode:
        irq_domain_free_fwnode(hbus->sysdata.fwnode);
unmap:
        iounmap(hbus->cfg_addr);
free_config:
        hv_free_config_window(hbus);
close:
        vmbus_close(hdev->channel);
destroy_wq:
        destroy_workqueue(hbus->wq);
free_dom:
        hv_put_dom_num(hbus->sysdata.domain);
free_bus:
        kfree(hbus);
        return ret;
}

static int hv_pci_bus_exit(struct hv_device *hdev, bool keep_devs)
{
        struct hv_pcibus_device *hbus = hv_get_drvdata(hdev);
        struct {
                struct pci_packet teardown_packet;
                u8 buffer[sizeof(struct pci_message)];
        } pkt;
        struct hv_pci_compl comp_pkt;
        struct hv_pci_dev *hpdev, *tmp;
        unsigned long flags;
        int ret;

        /*
         * After the host sends the RESCIND_CHANNEL message, it doesn't
         * access the per-channel ringbuffer any longer.
         */
        if (hdev->channel->rescind)
                return 0;

        if (!keep_devs) {
                /* Delete any children which might still exist. */
                spin_lock_irqsave(&hbus->device_list_lock, flags);
                list_for_each_entry_safe(hpdev, tmp, &hbus->children, list_entry) {
                        list_del(&hpdev->list_entry);
                        if (hpdev->pci_slot)
                                pci_destroy_slot(hpdev->pci_slot);
                        /* For the two refs got in new_pcichild_device() */
                        put_pcichild(hpdev);
                        put_pcichild(hpdev);
                }
                spin_unlock_irqrestore(&hbus->device_list_lock, flags);
        }

        ret = hv_send_resources_released(hdev);
        if (ret) {
                dev_err(&hdev->device,
                        "Couldn't send resources released packet(s)\n");
                return ret;
        }

        memset(&pkt.teardown_packet, 0, sizeof(pkt.teardown_packet));
        init_completion(&comp_pkt.host_event);
        pkt.teardown_packet.completion_func = hv_pci_generic_compl;
        pkt.teardown_packet.compl_ctxt = &comp_pkt;
        pkt.teardown_packet.message[0].type = PCI_BUS_D0EXIT;

        ret = vmbus_sendpacket(hdev->channel, &pkt.teardown_packet.message,
                               sizeof(struct pci_message),
                               (unsigned long)&pkt.teardown_packet,
                               VM_PKT_DATA_INBAND,
                               VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED);
        if (ret)
                return ret;

        if (wait_for_completion_timeout(&comp_pkt.host_event, 10 * HZ) == 0)
                return -ETIMEDOUT;

        return 0;
}

/**
 * hv_pci_remove() - Remove routine for this VMBus channel
 * @hdev:       VMBus's tracking struct for this root PCI bus
 *
 * Return: 0 on success, -errno on failure
 */
static int hv_pci_remove(struct hv_device *hdev)
{
        struct hv_pcibus_device *hbus;
        int ret;

        hbus = hv_get_drvdata(hdev);
        if (hbus->state == hv_pcibus_installed) {
                tasklet_disable(&hdev->channel->callback_event);
                hbus->state = hv_pcibus_removing;
                tasklet_enable(&hdev->channel->callback_event);
                destroy_workqueue(hbus->wq);
                hbus->wq = NULL;
                /*
                 * At this point, no work is running or can be scheduled
                 * on hbus-wq. We can't race with hv_pci_devices_present()
                 * or hv_pci_eject_device(), it's safe to proceed.
                 */

                /* Remove the bus from PCI's point of view. */
                pci_lock_rescan_remove();
                pci_stop_root_bus(hbus->pci_bus);
                hv_pci_remove_slots(hbus);
                pci_remove_root_bus(hbus->pci_bus);
                pci_unlock_rescan_remove();
        }

        ret = hv_pci_bus_exit(hdev, false);

        vmbus_close(hdev->channel);

        iounmap(hbus->cfg_addr);
        hv_free_config_window(hbus);
        pci_free_resource_list(&hbus->resources_for_children);
        hv_pci_free_bridge_windows(hbus);
        irq_domain_remove(hbus->irq_domain);
        irq_domain_free_fwnode(hbus->sysdata.fwnode);

        hv_put_dom_num(hbus->sysdata.domain);

        kfree(hbus);
        return ret;
}

static int hv_pci_suspend(struct hv_device *hdev)
{
        struct hv_pcibus_device *hbus = hv_get_drvdata(hdev);
        enum hv_pcibus_state old_state;
        int ret;

        /*
         * hv_pci_suspend() must make sure there are no pending work items
         * before calling vmbus_close(), since it runs in a process context
         * as a callback in dpm_suspend().  When it starts to run, the channel
         * callback hv_pci_onchannelcallback(), which runs in a tasklet
         * context, can be still running concurrently and scheduling new work
         * items onto hbus->wq in hv_pci_devices_present() and
         * hv_pci_eject_device(), and the work item handlers can access the
         * vmbus channel, which can be being closed by hv_pci_suspend(), e.g.
         * the work item handler pci_devices_present_work() ->
         * new_pcichild_device() writes to the vmbus channel.
         *
         * To eliminate the race, hv_pci_suspend() disables the channel
         * callback tasklet, sets hbus->state to hv_pcibus_removing, and
         * re-enables the tasklet. This way, when hv_pci_suspend() proceeds,
         * it knows that no new work item can be scheduled, and then it flushes
         * hbus->wq and safely closes the vmbus channel.
         */
        tasklet_disable(&hdev->channel->callback_event);

        /* Change the hbus state to prevent new work items. */
        old_state = hbus->state;
        if (hbus->state == hv_pcibus_installed)
                hbus->state = hv_pcibus_removing;

        tasklet_enable(&hdev->channel->callback_event);

        if (old_state != hv_pcibus_installed)
                return -EINVAL;

        flush_workqueue(hbus->wq);

        ret = hv_pci_bus_exit(hdev, true);
        if (ret)
                return ret;

        vmbus_close(hdev->channel);

        return 0;
}

static int hv_pci_restore_msi_msg(struct pci_dev *pdev, void *arg)
{
        struct msi_desc *entry;
        struct irq_data *irq_data;

        for_each_pci_msi_entry(entry, pdev) {
                irq_data = irq_get_irq_data(entry->irq);
                if (WARN_ON_ONCE(!irq_data))
                        return -EINVAL;

                hv_compose_msi_msg(irq_data, &entry->msg);
        }

        return 0;
}

/*
 * Upon resume, pci_restore_msi_state() -> ... ->  __pci_write_msi_msg()
 * directly writes the MSI/MSI-X registers via MMIO, but since Hyper-V
 * doesn't trap and emulate the MMIO accesses, here hv_compose_msi_msg()
 * must be used to ask Hyper-V to re-create the IOMMU Interrupt Remapping
 * Table entries.
 */
static void hv_pci_restore_msi_state(struct hv_pcibus_device *hbus)
{
        pci_walk_bus(hbus->pci_bus, hv_pci_restore_msi_msg, NULL);
}

static int hv_pci_resume(struct hv_device *hdev)
{
        struct hv_pcibus_device *hbus = hv_get_drvdata(hdev);
        enum pci_protocol_version_t version[1];
        int ret;

        hbus->state = hv_pcibus_init;

        ret = vmbus_open(hdev->channel, pci_ring_size, pci_ring_size, NULL, 0,
                         hv_pci_onchannelcallback, hbus);
        if (ret)
                return ret;

        /* Only use the version that was in use before hibernation. */
        version[0] = hbus->protocol_version;
        ret = hv_pci_protocol_negotiation(hdev, version, 1);
        if (ret)
                goto out;

        ret = hv_pci_query_relations(hdev);
        if (ret)
                goto out;

        ret = hv_pci_enter_d0(hdev);
        if (ret)
                goto out;

        ret = hv_send_resources_allocated(hdev);
        if (ret)
                goto out;

        prepopulate_bars(hbus);

        hv_pci_restore_msi_state(hbus);

        hbus->state = hv_pcibus_installed;
        return 0;
out:
        vmbus_close(hdev->channel);
        return ret;
}

static const struct hv_vmbus_device_id hv_pci_id_table[] = {
        /* PCI Pass-through Class ID */
        /* 44C4F61D-4444-4400-9D52-802E27EDE19F */
        { HV_PCIE_GUID, },
        { },
};

MODULE_DEVICE_TABLE(vmbus, hv_pci_id_table);

static struct hv_driver hv_pci_drv = {
        .name           = "hv_pci",
        .id_table       = hv_pci_id_table,
        .probe          = hv_pci_probe,
        .remove         = hv_pci_remove,
        .suspend        = hv_pci_suspend,
        .resume         = hv_pci_resume,
};

static void __exit exit_hv_pci_drv(void)
{
        vmbus_driver_unregister(&hv_pci_drv);

        hvpci_block_ops.read_block = NULL;
        hvpci_block_ops.write_block = NULL;
        hvpci_block_ops.reg_blk_invalidate = NULL;
}

static int __init init_hv_pci_drv(void)
{
        if (!hv_is_hyperv_initialized())
                return -ENODEV;

        /* Set the invalid domain number's bit, so it will not be used */
        set_bit(HVPCI_DOM_INVALID, hvpci_dom_map);

        /* Initialize PCI block r/w interface */
        hvpci_block_ops.read_block = hv_read_config_block;
        hvpci_block_ops.write_block = hv_write_config_block;
        hvpci_block_ops.reg_blk_invalidate = hv_register_block_invalidate;

        return vmbus_driver_register(&hv_pci_drv);
}

module_init(init_hv_pci_drv);
module_exit(exit_hv_pci_drv);

MODULE_DESCRIPTION("Hyper-V PCI");
MODULE_LICENSE("GPL v2");