Connect the x86 instruction decoder and emulator to the MSHV backend
to handle intercepted instructions. This enables software emulation
of MMIO operations in MSHV guests. MSHV has a translate_gva hypercall
that is used to accessing the physical guest memory.
A guest might read from unmapped memory regions (e.g. OVMF will probe
0xfed40000 for a vTPM). In those cases 0xFF bytes is returned instead of
aborting the execution.
Signed-off-by: Magnus Kulke <magnusku...@linux.microsoft.com>
---
accel/mshv/mem.c | 65 +++++++++++++++++++
accel/mshv/mshv-all.c | 2 +-
include/system/mshv.h | 6 +-
target/i386/mshv/mshv-cpu.c | 126 +++++++++++++++++++++++++++++++++++-
4 files changed, 196 insertions(+), 3 deletions(-)
diff --git a/accel/mshv/mem.c b/accel/mshv/mem.c
index 8039f35680..150fb723af 100644
--- a/accel/mshv/mem.c
+++ b/accel/mshv/mem.c
@@ -58,6 +58,71 @@ static int map_or_unmap(int vm_fd, const MshvMemoryRegion
*mr, bool map)
return set_guest_memory(vm_fd, ®ion);
}
+static int handle_unmapped_mmio_region_read(uint64_t gpa, uint64_t size,
+ uint8_t *data)
+{
+ warn_report("read from unmapped mmio region gpa=0x%lx size=%lu", gpa,
size);
+
+ if (size == 0 || size > 8) {
+ error_report("invalid size %lu for reading from unmapped mmio region",
+ size);
+ return -1;
+ }
+
+ memset(data, 0xFF, size);
+
+ return 0;
+}
+
+int mshv_guest_mem_read(uint64_t gpa, uint8_t *data, uintptr_t size,
+ bool is_secure_mode, bool instruction_fetch)
+{
+ int ret;
+ MemTxAttrs memattr = { .secure = is_secure_mode };
+
+ if (instruction_fetch) {
+ trace_mshv_insn_fetch(gpa, size);
+ } else {
+ trace_mshv_mem_read(gpa, size);
+ }
+
+ ret = address_space_rw(&address_space_memory, gpa, memattr, (void *)data,
+ size, false);
+ if (ret == MEMTX_OK) {
+ return 0;
+ }
+
+ if (ret == MEMTX_DECODE_ERROR) {
+ return handle_unmapped_mmio_region_read(gpa, size, data);
+ }
+
+ error_report("failed to read guest memory at 0x%lx", gpa);
+ return -1;
+}
+
+int mshv_guest_mem_write(uint64_t gpa, const uint8_t *data, uintptr_t size,
+ bool is_secure_mode)
+{
+ int ret;
+ MemTxAttrs memattr = { .secure = is_secure_mode };
+
+ trace_mshv_mem_write(gpa, size);
+ ret = address_space_rw(&address_space_memory, gpa, memattr, (void *)data,
+ size, true);
+ if (ret == MEMTX_OK) {
+ return 0;
+ }
+
+ if (ret == MEMTX_DECODE_ERROR) {
+ warn_report("write to unmapped mmio region gpa=0x%lx size=%lu", gpa,
+ size);
+ return 0;
+ }
+
+ error_report("Failed to write guest memory");
+ return -1;
+}
+
static int set_memory(const MshvMemoryRegion *mshv_mr, bool add)
{
int ret = 0;
diff --git a/accel/mshv/mshv-all.c b/accel/mshv/mshv-all.c
index 65166e82b0..4f4c4b9639 100644
--- a/accel/mshv/mshv-all.c
+++ b/accel/mshv/mshv-all.c
@@ -431,7 +431,7 @@ static int mshv_init(AccelState *as, MachineState *ms)
return -1;
}
- mshv_init_cpu_logic();
+ mshv_init_mmio_emu();
mshv_init_msicontrol();
diff --git a/include/system/mshv.h b/include/system/mshv.h
index 7f2a7dcb8a..c527acc08c 100644
--- a/include/system/mshv.h
+++ b/include/system/mshv.h
@@ -103,7 +103,7 @@ typedef enum MshvVmExit {
MshvVmExitSpecial = 2,
} MshvVmExit;
-void mshv_init_cpu_logic(void);
+void mshv_init_mmio_emu(void);
int mshv_create_vcpu(int vm_fd, uint8_t vp_index, int *cpu_fd);
void mshv_remove_vcpu(int vm_fd, int cpu_fd);
int mshv_configure_vcpu(const CPUState *cpu, const MshvFPU *fpu, uint64_t
xcr0);
@@ -154,6 +154,10 @@ typedef struct MshvMemoryRegion {
int mshv_add_mem(int vm_fd, const MshvMemoryRegion *mr);
int mshv_remove_mem(int vm_fd, const MshvMemoryRegion *mr);
+int mshv_guest_mem_read(uint64_t gpa, uint8_t *data, uintptr_t size,
+ bool is_secure_mode, bool instruction_fetch);
+int mshv_guest_mem_write(uint64_t gpa, const uint8_t *data, uintptr_t size,
+ bool is_secure_mode);
void mshv_set_phys_mem(MshvMemoryListener *mml, MemoryRegionSection *section,
bool add);
diff --git a/target/i386/mshv/mshv-cpu.c b/target/i386/mshv/mshv-cpu.c
index c2c7934343..673c90f865 100644
--- a/target/i386/mshv/mshv-cpu.c
+++ b/target/i386/mshv/mshv-cpu.c
@@ -103,6 +103,34 @@ static enum hv_register_name FPU_REGISTER_NAMES[26] = {
HV_X64_REGISTER_XMM_CONTROL_STATUS,
};
+static int translate_gva(int cpu_fd, uint64_t gva, uint64_t *gpa,
+ uint64_t flags)
+{
+ int ret;
+ union hv_translate_gva_result result = { 0 };
+
+ *gpa = 0;
+ mshv_translate_gva args = {
+ .gva = gva,
+ .flags = flags,
+ .gpa = gpa,
+ .result = &result,
+ };
+
+ ret = ioctl(cpu_fd, MSHV_TRANSLATE_GVA, &args);
+ if (ret < 0) {
+ error_report("failed to invoke gpa->gva translation");
+ return -errno;
+ }
+ if (result.result_code != HV_TRANSLATE_GVA_SUCCESS) {
+ error_report("failed to translate gva (" TARGET_FMT_lx ") to gpa",
gva);
+ return -1;
+
+ }
+
+ return 0;
+}
+
int mshv_set_generic_regs(int cpu_fd, hv_register_assoc *assocs, size_t n_regs)
{
struct mshv_vp_registers input = {
@@ -922,8 +950,104 @@ int mshv_create_vcpu(int vm_fd, uint8_t vp_index, int
*cpu_fd)
return 0;
}
-void mshv_init_cpu_logic(void)
+static int guest_mem_read_with_gva(const CPUState *cpu, uint64_t gva,
+ uint8_t *data, uintptr_t size,
+ bool fetch_instruction)
+{
+ int ret;
+ uint64_t gpa, flags;
+ int cpu_fd = mshv_vcpufd(cpu);
+
+ flags = HV_TRANSLATE_GVA_VALIDATE_READ;
+ ret = translate_gva(cpu_fd, gva, &gpa, flags);
+ if (ret < 0) {
+ error_report("failed to translate gva to gpa");
+ return -1;
+ }
+
+ ret = mshv_guest_mem_read(gpa, data, size, false, fetch_instruction);
+ if (ret < 0) {
+ error_report("failed to read from guest memory");
+ return -1;
+ }
+
+ return 0;
+}
+
+static int guest_mem_write_with_gva(const CPUState *cpu, uint64_t gva,
+ const uint8_t *data, uintptr_t size)
+{
+ int ret;
+ uint64_t gpa, flags;
+ int cpu_fd = mshv_vcpufd(cpu);
+
+ flags = HV_TRANSLATE_GVA_VALIDATE_WRITE;
+ ret = translate_gva(cpu_fd, gva, &gpa, flags);
+ if (ret < 0) {
+ error_report("failed to translate gva to gpa");
+ return -1;
+ }
+ ret = mshv_guest_mem_write(gpa, data, size, false);
+ if (ret < 0) {
+ error_report("failed to write to guest memory");
+ return -1;
+ }
+ return 0;
+}
+
+static void write_mem(CPUState *cpu, void *data, target_ulong addr, int bytes)
+{
+ if (guest_mem_write_with_gva(cpu, addr, data, bytes) < 0) {
+ error_report("failed to write memory");
+ abort();
+ }
+}
+
+static void read_mem(CPUState *cpu, void *data, target_ulong addr, int bytes)
+{
+ if (guest_mem_read_with_gva(cpu, addr, data, bytes, false) < 0) {
+ error_report("failed to read memory");
+ abort();
+ }
+}
+
+static void fetch_instruction(CPUState *cpu, void *data,
+ target_ulong addr, int bytes)
+{
+ if (guest_mem_read_with_gva(cpu, addr, data, bytes, true) < 0) {
+ error_report("failed to fetch instruction");
+ abort();
+ }
+}
+
+static void read_segment_descriptor(CPUState *cpu,
+ struct x86_segment_descriptor *desc,
+ enum X86Seg seg_idx)
+{
+ bool ret;
+ X86CPU *x86_cpu = X86_CPU(cpu);
+ CPUX86State *env = &x86_cpu->env;
+ SegmentCache *seg = &env->segs[seg_idx];
+ x86_segment_selector sel = { .sel = seg->selector & 0xFFFF };
+
+ ret = x86_read_segment_descriptor(cpu, desc, sel);
+ if (ret == false) {
+ error_report("failed to read segment descriptor");
+ abort();
+ }
+}
+
+static const struct x86_emul_ops mshv_x86_emul_ops = {
+ .fetch_instruction = fetch_instruction,
+ .read_mem = read_mem,
+ .write_mem = write_mem,
+ .read_segment_descriptor = read_segment_descriptor,
+};
+
+void mshv_init_mmio_emu(void)
{
+ init_decoder();
+ init_emu(&mshv_x86_emul_ops);
}
void mshv_arch_init_vcpu(CPUState *cpu)
--
2.34.1
