arch/arm64/kvm/mmio.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Copyright (C) 2012 - Virtual Open Systems and Columbia University
   4  * Author: Christoffer Dall <c.dall@virtualopensystems.com>
   5  */
   6
   7 #include <linux/kvm_host.h>
   8 #include <asm/kvm_emulate.h>
   9 #include <trace/events/kvm.h>
  10
  11 #include "trace.h"
  12
  13 void kvm_mmio_write_buf(void *buf, unsigned int len, unsigned long data)
  14 {
  15         void *datap = NULL;
  16         union {
  17                 u8      byte;
  18                 u16     hword;
  19                 u32     word;
  20                 u64     dword;
  21         } tmp;
  22
  23         switch (len) {
  24         case 1:
  25                 tmp.byte        = data;
  26                 datap           = &tmp.byte;
  27                 break;
  28         case 2:
  29                 tmp.hword       = data;
  30                 datap           = &tmp.hword;
  31                 break;
  32         case 4:
  33                 tmp.word        = data;
  34                 datap           = &tmp.word;
  35                 break;
  36         case 8:
  37                 tmp.dword       = data;
  38                 datap           = &tmp.dword;
  39                 break;
  40         }
  41
  42         memcpy(buf, datap, len);
  43 }
  44
  45 unsigned long kvm_mmio_read_buf(const void *buf, unsigned int len)
  46 {
  47         unsigned long data = 0;
  48         union {
  49                 u16     hword;
  50                 u32     word;
  51                 u64     dword;
  52         } tmp;
  53
  54         switch (len) {
  55         case 1:
  56                 data = *(u8 *)buf;
  57                 break;
  58         case 2:
  59                 memcpy(&tmp.hword, buf, len);
  60                 data = tmp.hword;
  61                 break;
  62         case 4:
  63                 memcpy(&tmp.word, buf, len);
  64                 data = tmp.word;
  65                 break;
  66         case 8:
  67                 memcpy(&tmp.dword, buf, len);
  68                 data = tmp.dword;
  69                 break;
  70         }
  71
  72         return data;
  73 }
  74
  75 /**
  76  * kvm_handle_mmio_return -- Handle MMIO loads after user space emulation
  77  *                           or in-kernel IO emulation
  78  *
  79  * @vcpu: The VCPU pointer
  80  */
  81 int kvm_handle_mmio_return(struct kvm_vcpu *vcpu)
  82 {
  83         unsigned long data;
  84         unsigned int len;
  85         int mask;
  86
  87         /* Detect an already handled MMIO return */
  88         if (unlikely(!vcpu->mmio_needed))
  89                 return 0;
  90
  91         vcpu->mmio_needed = 0;
  92
  93         if (!kvm_vcpu_dabt_iswrite(vcpu)) {
  94                 struct kvm_run *run = vcpu->run;
  95
  96                 len = kvm_vcpu_dabt_get_as(vcpu);
  97                 data = kvm_mmio_read_buf(run->mmio.data, len);
  98
  99                 if (kvm_vcpu_dabt_issext(vcpu) &&
 100                     len < sizeof(unsigned long)) {
 101                         mask = 1U << ((len * 8) - 1);
 102                         data = (data ^ mask) - mask;
 103                 }
 104
 105                 if (!kvm_vcpu_dabt_issf(vcpu))
 106                         data = data & 0xffffffff;
 107
 108                 trace_kvm_mmio(KVM_TRACE_MMIO_READ, len, run->mmio.phys_addr,
 109                                &data);
 110                 data = vcpu_data_host_to_guest(vcpu, data, len);
 111                 vcpu_set_reg(vcpu, kvm_vcpu_dabt_get_rd(vcpu), data);
 112         }
 113
 114         /*
 115          * The MMIO instruction is emulated and should not be re-executed
 116          * in the guest.
 117          */
 118         kvm_incr_pc(vcpu);
 119
 120         return 0;
 121 }
 122
 123 int io_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa)
 124 {
 125         struct kvm_run *run = vcpu->run;
 126         unsigned long data;
 127         unsigned long rt;
 128         int ret;
 129         bool is_write;
 130         int len;
 131         u8 data_buf[8];
 132
 133         /*
 134          * No valid syndrome? Ask userspace for help if it has
 135          * volunteered to do so, and bail out otherwise.
 136          */
 137         if (!kvm_vcpu_dabt_isvalid(vcpu)) {
 138                 if (test_bit(KVM_ARCH_FLAG_RETURN_NISV_IO_ABORT_TO_USER,
 139                              &vcpu->kvm->arch.flags)) {
 140                         run->exit_reason = KVM_EXIT_ARM_NISV;
 141                         run->arm_nisv.esr_iss = kvm_vcpu_dabt_iss_nisv_sanitized(vcpu);
 142                         run->arm_nisv.fault_ipa = fault_ipa;
 143                         return 0;
 144                 }
 145
 146                 kvm_pr_unimpl("Data abort outside memslots with no valid syndrome info\n");
 147                 return -ENOSYS;
 148         }
 149
 150         /*
 151          * Prepare MMIO operation. First decode the syndrome data we get
 152          * from the CPU. Then try if some in-kernel emulation feels
 153          * responsible, otherwise let user space do its magic.
 154          */
 155         is_write = kvm_vcpu_dabt_iswrite(vcpu);
 156         len = kvm_vcpu_dabt_get_as(vcpu);
 157         rt = kvm_vcpu_dabt_get_rd(vcpu);
 158
 159         if (is_write) {
 160                 data = vcpu_data_guest_to_host(vcpu, vcpu_get_reg(vcpu, rt),
 161                                                len);
 162
 163                 trace_kvm_mmio(KVM_TRACE_MMIO_WRITE, len, fault_ipa, &data);
 164                 kvm_mmio_write_buf(data_buf, len, data);
 165
 166                 ret = kvm_io_bus_write(vcpu, KVM_MMIO_BUS, fault_ipa, len,
 167                                        data_buf);
 168         } else {
 169                 trace_kvm_mmio(KVM_TRACE_MMIO_READ_UNSATISFIED, len,
 170                                fault_ipa, NULL);
 171
 172                 ret = kvm_io_bus_read(vcpu, KVM_MMIO_BUS, fault_ipa, len,
 173                                       data_buf);
 174         }
 175
 176         /* Now prepare kvm_run for the potential return to userland. */
 177         run->mmio.is_write      = is_write;
 178         run->mmio.phys_addr     = fault_ipa;
 179         run->mmio.len           = len;
 180         vcpu->mmio_needed       = 1;
 181
 182         if (!ret) {
 183                 /* We handled the access successfully in the kernel. */
 184                 if (!is_write)
 185                         memcpy(run->mmio.data, data_buf, len);
 186                 vcpu->stat.mmio_exit_kernel++;
 187                 kvm_handle_mmio_return(vcpu);
 188                 return 1;
 189         }
 190
 191         if (is_write)
 192                 memcpy(run->mmio.data, data_buf, len);
 193         vcpu->stat.mmio_exit_user++;
 194         run->exit_reason        = KVM_EXIT_MMIO;
 195         return 0;
 196 }