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target/i386/mshv: Integrate x86 instruction decoder/emulator

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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 <magnuskulke@linux.microsoft.com>
Link: https://lore.kernel.org/r/20250916164847.77883-21-magnuskulke@linux.microsoft.com
[mshv.h/mshv_int.h split. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Magnus Kulke 2025-09-16 18:48:40 +02:00 • committed by Paolo Bonzini
parent f38e2a63e5
commit 9bc6a1d296
3 changed files with 204 additions and 0 deletions
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65
accel/mshv/mem.c
View file

@ -59,6 +59,71 @@ static int map_or_unmap(int vm_fd, const MshvMemoryRegion *mr, bool map)
return set_guest_memory(vm_fd, &region);
}
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;