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         /* Detect an already handled MMIO return */
  90         if (unlikely(!vcpu->mmio_needed))
  91                 return 0;
  92
  93         vcpu->mmio_needed = 0;
  94
  95         if (!run->mmio.is_write) {
  96                 len = run->mmio.len;
  97                 if (len > sizeof(unsigned long))
  98                         return -EINVAL;
  99
 100                 data = kvm_mmio_read_buf(run->mmio.data, len);
 101
 102                 if (vcpu->arch.mmio_decode.sign_extend &&
 103                     len < sizeof(unsigned long)) {
 104                         mask = 1U << ((len * 8) - 1);
 105                         data = (data ^ mask) - mask;
 106                 }
 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, vcpu->arch.mmio_decode.rt, data);
 112         }
 113
 114         /*
 115          * The MMIO instruction is emulated and should not be re-executed
 116          * in the guest.
 117          */
 118         kvm_skip_instr(vcpu, kvm_vcpu_trap_il_is32bit(vcpu));
 119
 120         return 0;
 121 }
 122
 123 static int decode_hsr(struct kvm_vcpu *vcpu, bool *is_write, int *len)
 124 {
 125         unsigned long rt;
 126         int access_size;
 127         bool sign_extend;
 128
 129         if (kvm_vcpu_dabt_iss1tw(vcpu)) {
 130                 /* page table accesses IO mem: tell guest to fix its TTBR */
 131                 kvm_inject_dabt(vcpu, kvm_vcpu_get_hfar(vcpu));
 132                 return 1;
 133         }
 134
 135         access_size = kvm_vcpu_dabt_get_as(vcpu);
 136         if (unlikely(access_size < 0))
 137                 return access_size;
 138
 139         *is_write = kvm_vcpu_dabt_iswrite(vcpu);
 140         sign_extend = kvm_vcpu_dabt_issext(vcpu);
 141         rt = kvm_vcpu_dabt_get_rd(vcpu);
 142
 143         *len = access_size;
 144         vcpu->arch.mmio_decode.sign_extend = sign_extend;
 145         vcpu->arch.mmio_decode.rt = rt;
 146
 147         return 0;
 148 }
 149
 150 int io_mem_abort(struct kvm_vcpu *vcpu, struct kvm_run *run,
 151                  phys_addr_t fault_ipa)
 152 {
 153         unsigned long data;
 154         unsigned long rt;
 155         int ret;
 156         bool is_write;
 157         int len;
 158         u8 data_buf[8];
 159
 160         /*
 161          * Prepare MMIO operation. First decode the syndrome data we get
 162          * from the CPU. Then try if some in-kernel emulation feels
 163          * responsible, otherwise let user space do its magic.
 164          */
 165         if (kvm_vcpu_dabt_isvalid(vcpu)) {
 166                 ret = decode_hsr(vcpu, &is_write, &len);
 167                 if (ret)
 168                         return ret;
 169         } else {
 170                 kvm_err("load/store instruction decoding not implemented\n");
 171                 return -ENOSYS;
 172         }
 173
 174         rt = vcpu->arch.mmio_decode.rt;
 175
 176         if (is_write) {
 177                 data = vcpu_data_guest_to_host(vcpu, vcpu_get_reg(vcpu, rt),
 178                                                len);
 179
 180                 trace_kvm_mmio(KVM_TRACE_MMIO_WRITE, len, fault_ipa, &data);
 181                 kvm_mmio_write_buf(data_buf, len, data);
 182
 183                 ret = kvm_io_bus_write(vcpu, KVM_MMIO_BUS, fault_ipa, len,
 184                                        data_buf);
 185         } else {
 186                 trace_kvm_mmio(KVM_TRACE_MMIO_READ_UNSATISFIED, len,
 187                                fault_ipa, NULL);
 188
 189                 ret = kvm_io_bus_read(vcpu, KVM_MMIO_BUS, fault_ipa, len,
 190                                       data_buf);
 191         }
 192
 193         /* Now prepare kvm_run for the potential return to userland. */
 194         run->mmio.is_write      = is_write;
 195         run->mmio.phys_addr     = fault_ipa;
 196         run->mmio.len           = len;
 197         vcpu->mmio_needed       = 1;
 198
 199         if (!ret) {
 200                 /* We handled the access successfully in the kernel. */
 201                 if (!is_write)
 202                         memcpy(run->mmio.data, data_buf, len);
 203                 vcpu->stat.mmio_exit_kernel++;
 204                 kvm_handle_mmio_return(vcpu, run);
 205                 return 1;
 206         }
 207
 208         if (is_write)
 209                 memcpy(run->mmio.data, data_buf, len);
 210         vcpu->stat.mmio_exit_user++;
 211         run->exit_reason        = KVM_EXIT_MMIO;
 212         return 0;
 213 }