arch/arm64/kernel/paravirt.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  *
   4  * Copyright (C) 2013 Citrix Systems
   5  *
   6  * Author: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
   7  */
   8
   9 #define pr_fmt(fmt) "arm-pv: " fmt
  10
  11 #include <linux/arm-smccc.h>
  12 #include <linux/cpuhotplug.h>
  13 #include <linux/export.h>
  14 #include <linux/io.h>
  15 #include <linux/jump_label.h>
  16 #include <linux/printk.h>
  17 #include <linux/psci.h>
  18 #include <linux/reboot.h>
  19 #include <linux/slab.h>
  20 #include <linux/types.h>
  21
  22 #include <asm/paravirt.h>
  23 #include <asm/pvclock-abi.h>
  24 #include <asm/smp_plat.h>
  25
  26 struct static_key paravirt_steal_enabled;
  27 struct static_key paravirt_steal_rq_enabled;
  28
  29 struct paravirt_patch_template pv_ops;
  30 EXPORT_SYMBOL_GPL(pv_ops);
  31
  32 struct pv_time_stolen_time_region {
  33         struct pvclock_vcpu_stolen_time *kaddr;
  34 };
  35
  36 static DEFINE_PER_CPU(struct pv_time_stolen_time_region, stolen_time_region);
  37
  38 static bool steal_acc = true;
  39 static int __init parse_no_stealacc(char *arg)
  40 {
  41         steal_acc = false;
  42         return 0;
  43 }
  44
  45 early_param("no-steal-acc", parse_no_stealacc);
  46
  47 /* return stolen time in ns by asking the hypervisor */
  48 static u64 pv_steal_clock(int cpu)
  49 {
  50         struct pv_time_stolen_time_region *reg;
  51
  52         reg = per_cpu_ptr(&stolen_time_region, cpu);
  53
  54         /*
  55          * paravirt_steal_clock() may be called before the CPU
  56          * online notification callback runs. Until the callback
  57          * has run we just return zero.
  58          */
  59         if (!reg->kaddr)
  60                 return 0;
  61
  62         return le64_to_cpu(READ_ONCE(reg->kaddr->stolen_time));
  63 }
  64
  65 static int stolen_time_cpu_down_prepare(unsigned int cpu)
  66 {
  67         struct pv_time_stolen_time_region *reg;
  68
  69         reg = this_cpu_ptr(&stolen_time_region);
  70         if (!reg->kaddr)
  71                 return 0;
  72
  73         memunmap(reg->kaddr);
  74         memset(reg, 0, sizeof(*reg));
  75
  76         return 0;
  77 }
  78
  79 static int stolen_time_cpu_online(unsigned int cpu)
  80 {
  81         struct pv_time_stolen_time_region *reg;
  82         struct arm_smccc_res res;
  83
  84         reg = this_cpu_ptr(&stolen_time_region);
  85
  86         arm_smccc_1_1_invoke(ARM_SMCCC_HV_PV_TIME_ST, &res);
  87
  88         if (res.a0 == SMCCC_RET_NOT_SUPPORTED)
  89                 return -EINVAL;
  90
  91         reg->kaddr = memremap(res.a0,
  92                               sizeof(struct pvclock_vcpu_stolen_time),
  93                               MEMREMAP_WB);
  94
  95         if (!reg->kaddr) {
  96                 pr_warn("Failed to map stolen time data structure\n");
  97                 return -ENOMEM;
  98         }
  99
 100         if (le32_to_cpu(reg->kaddr->revision) != 0 ||
 101             le32_to_cpu(reg->kaddr->attributes) != 0) {
 102                 pr_warn_once("Unexpected revision or attributes in stolen time data\n");
 103                 return -ENXIO;
 104         }
 105
 106         return 0;
 107 }
 108
 109 static int __init pv_time_init_stolen_time(void)
 110 {
 111         int ret;
 112
 113         ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN,
 114                                 "hypervisor/arm/pvtime:online",
 115                                 stolen_time_cpu_online,
 116                                 stolen_time_cpu_down_prepare);
 117         if (ret < 0)
 118                 return ret;
 119         return 0;
 120 }
 121
 122 static bool __init has_pv_steal_clock(void)
 123 {
 124         struct arm_smccc_res res;
 125
 126         /* To detect the presence of PV time support we require SMCCC 1.1+ */
 127         if (arm_smccc_1_1_get_conduit() == SMCCC_CONDUIT_NONE)
 128                 return false;
 129
 130         arm_smccc_1_1_invoke(ARM_SMCCC_ARCH_FEATURES_FUNC_ID,
 131                              ARM_SMCCC_HV_PV_TIME_FEATURES, &res);
 132
 133         if (res.a0 != SMCCC_RET_SUCCESS)
 134                 return false;
 135
 136         arm_smccc_1_1_invoke(ARM_SMCCC_HV_PV_TIME_FEATURES,
 137                              ARM_SMCCC_HV_PV_TIME_ST, &res);
 138
 139         return (res.a0 == SMCCC_RET_SUCCESS);
 140 }
 141
 142 int __init pv_time_init(void)
 143 {
 144         int ret;
 145
 146         if (!has_pv_steal_clock())
 147                 return 0;
 148
 149         ret = pv_time_init_stolen_time();
 150         if (ret)
 151                 return ret;
 152
 153         pv_ops.time.steal_clock = pv_steal_clock;
 154
 155         static_key_slow_inc(&paravirt_steal_enabled);
 156         if (steal_acc)
 157                 static_key_slow_inc(&paravirt_steal_rq_enabled);
 158
 159         pr_info("using stolen time PV\n");
 160
 161         return 0;
 162 }