virt/kvm/arm/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_mmio.h>
   9 #include <asm/kvm_emulate.h>
  10 #include <trace/events/kvm.h>
  11
  12 #include "trace.h"
  13
  14 void kvm_mmio_write_buf(void *buf, unsigned int len, unsigned long data)
  15 {
  16         void *datap = NULL;
  17         union {
  18                 u8      byte;
  19                 u16     hword;
  20                 u32     word;
  21                 u64     dword;
  22         } tmp;
  23
  24         switch (len) {
  25         case 1:
  26                 tmp.byte        = data;
  27                 datap           = &tmp.byte;
  28                 break;
  29         case 2:
  30                 tmp.hword       = data;
  31                 datap           = &tmp.hword;
  32                 break;
  33         case 4:
  34                 tmp.word        = data;
  35                 datap           = &tmp.word;
  36                 break;
  37         case 8:
  38                 tmp.dword       = data;
  39                 datap           = &tmp.dword;
  40                 break;
  41         }
  42
  43         memcpy(buf, datap, len);
  44 }
  45
  46 unsigned long kvm_mmio_read_buf(const void *buf, unsigned int len)
  47 {
  48         unsigned long data = 0;
  49         union {
  50                 u16     hword;
  51                 u32     word;
  52                 u64     dword;
  53         } tmp;
  54
  55         switch (len) {
  56         case 1:
  57                 data = *(u8 *)buf;
  58                 break;
  59         case 2:
  60                 memcpy(&tmp.hword, buf, len);
  61                 data = tmp.hword;
  62                 break;
  63         case 4:
  64                 memcpy(&tmp.word, buf, len);
  65                 data = tmp.word;
  66                 break;
  67         case 8:
  68                 memcpy(&tmp.dword, buf, len);
  69                 data = tmp.dword;
  70                 break;
  71         }
  72
  73         return data;
  74 }
  75
  76 /**
  77  * kvm_handle_mmio_return -- Handle MMIO loads after user space emulation
  78  *                           or in-kernel IO emulation
  79  *
  80  * @vcpu: The VCPU pointer
  81  * @run:  The VCPU run struct containing the mmio data
  82  */
  83 int kvm_handle_mmio_return(struct kvm_vcpu *vcpu, struct kvm_run *run)
  84 {
  85         unsigned long data;
  86         unsigned int len;
  87         int mask;
  88
  89         if (!run->mmio.is_write) {
  90                 len = run->mmio.len;
  91                 if (len > sizeof(unsigned long))
  92                         return -EINVAL;
  93
  94                 data = kvm_mmio_read_buf(run->mmio.data, len);
  95
  96                 if (vcpu->arch.mmio_decode.sign_extend &&
  97                     len < sizeof(unsigned long)) {
  98                         mask = 1U << ((len * 8) - 1);
  99                         data = (data ^ mask) - mask;
 100                 }
 101
 102                 trace_kvm_mmio(KVM_TRACE_MMIO_READ, len, run->mmio.phys_addr,
 103                                &data);
 104                 data = vcpu_data_host_to_guest(vcpu, data, len);
 105                 vcpu_set_reg(vcpu, vcpu->arch.mmio_decode.rt, data);
 106         }
 107
 108         /*
 109          * The MMIO instruction is emulated and should not be re-executed
 110          * in the guest.
 111          */
 112         kvm_skip_instr(vcpu, kvm_vcpu_trap_il_is32bit(vcpu));
 113
 114         return 0;
 115 }
 116
 117 static int decode_hsr(struct kvm_vcpu *vcpu, bool *is_write, int *len)
 118 {
 119         unsigned long rt;
 120         int access_size;
 121         bool sign_extend;
 122
 123         if (kvm_vcpu_dabt_iss1tw(vcpu)) {
 124                 /* page table accesses IO mem: tell guest to fix its TTBR */
 125                 kvm_inject_dabt(vcpu, kvm_vcpu_get_hfar(vcpu));
 126                 return 1;
 127         }
 128
 129         access_size = kvm_vcpu_dabt_get_as(vcpu);
 130         if (unlikely(access_size < 0))
 131                 return access_size;
 132
 133         *is_write = kvm_vcpu_dabt_iswrite(vcpu);
 134         sign_extend = kvm_vcpu_dabt_issext(vcpu);
 135         rt = kvm_vcpu_dabt_get_rd(vcpu);
 136
 137         *len = access_size;
 138         vcpu->arch.mmio_decode.sign_extend = sign_extend;
 139         vcpu->arch.mmio_decode.rt = rt;
 140
 141         return 0;
 142 }
 143
 144 int io_mem_abort(struct kvm_vcpu *vcpu, struct kvm_run *run,
 145                  phys_addr_t fault_ipa)
 146 {
 147         unsigned long data;
 148         unsigned long rt;
 149         int ret;
 150         bool is_write;
 151         int len;
 152         u8 data_buf[8];
 153
 154         /*
 155          * Prepare MMIO operation. First decode the syndrome data we get
 156          * from the CPU. Then try if some in-kernel emulation feels
 157          * responsible, otherwise let user space do its magic.
 158          */
 159         if (kvm_vcpu_dabt_isvalid(vcpu)) {
 160                 ret = decode_hsr(vcpu, &is_write, &len);
 161                 if (ret)
 162                         return ret;
 163         } else {
 164                 kvm_err("load/store instruction decoding not implemented\n");
 165                 return -ENOSYS;
 166         }
 167
 168         rt = vcpu->arch.mmio_decode.rt;
 169
 170         if (is_write) {
 171                 data = vcpu_data_guest_to_host(vcpu, vcpu_get_reg(vcpu, rt),
 172                                                len);
 173
 174                 trace_kvm_mmio(KVM_TRACE_MMIO_WRITE, len, fault_ipa, &data);
 175                 kvm_mmio_write_buf(data_buf, len, data);
 176
 177                 ret = kvm_io_bus_write(vcpu, KVM_MMIO_BUS, fault_ipa, len,
 178                                        data_buf);
 179         } else {
 180                 trace_kvm_mmio(KVM_TRACE_MMIO_READ_UNSATISFIED, len,
 181                                fault_ipa, NULL);
 182
 183                 ret = kvm_io_bus_read(vcpu, KVM_MMIO_BUS, fault_ipa, len,
 184                                       data_buf);
 185         }
 186
 187         /* Now prepare kvm_run for the potential return to userland. */
 188         run->mmio.is_write      = is_write;
 189         run->mmio.phys_addr     = fault_ipa;
 190         run->mmio.len           = len;
 191
 192         if (!ret) {
 193                 /* We handled the access successfully in the kernel. */
 194                 if (!is_write)
 195                         memcpy(run->mmio.data, data_buf, len);
 196                 vcpu->stat.mmio_exit_kernel++;
 197                 kvm_handle_mmio_return(vcpu, run);
 198                 return 1;
 199         }
 200
 201         if (is_write)
 202                 memcpy(run->mmio.data, data_buf, len);
 203         vcpu->stat.mmio_exit_user++;
 204         run->exit_reason        = KVM_EXIT_MMIO;
 205         return 0;
 206 }