mov (%rax), %ax is a 16-bit data MOV_FROM_MEM that will emit
0x66 0x8b 0x00.
0x66 is the operand-size override prefix which we currently do not support.
We should support it, as we can find this opcode, for example, for some
mmconfig space access from Linux (e.g., pci_generic_config_read).
This also adds appropriate mmio-access tests.
Tested in QEMU virtual target.
Signed-off-by: Ralf Ramsauer <[email protected]>
---
hypervisor/arch/x86/include/asm/processor.h | 1 +
hypervisor/arch/x86/mmio.c | 37 +++++++++++++++++----
inmates/tests/x86/mmio-access-32.c | 4 +++
inmates/tests/x86/mmio-access.c | 4 +++
4 files changed, 40 insertions(+), 6 deletions(-)
diff --git a/hypervisor/arch/x86/include/asm/processor.h
b/hypervisor/arch/x86/include/asm/processor.h
index 70a6c3ff..d8111690 100644
--- a/hypervisor/arch/x86/include/asm/processor.h
+++ b/hypervisor/arch/x86/include/asm/processor.h
@@ -145,6 +145,7 @@
#define X86_REX_CODE 4
+#define X86_PREFIX_OP_SZ 0x66
#define X86_PREFIX_ADDR_SZ 0x67
#define X86_OP_MOVZX_OPC1 0x0f
diff --git a/hypervisor/arch/x86/mmio.c b/hypervisor/arch/x86/mmio.c
index b234bd79..6d9ad1c5 100644
--- a/hypervisor/arch/x86/mmio.c
+++ b/hypervisor/arch/x86/mmio.c
@@ -79,6 +79,26 @@ static unsigned int get_address_width(bool has_addrsz_prefix)
(!!(cs_attr & VCPU_CS_DB) ^ has_addrsz_prefix) ? 4 : 2;
}
+static unsigned int get_op_width(bool has_rex_w, bool has_opsz_prefix)
+{
+ u16 cs_attr;
+ bool long_mode;
+
+ /* Op size prefix is ignored if rex.w = 1 */
+ if (has_rex_w)
+ return 8;
+
+ cs_attr = vcpu_vendor_get_cs_attr();
+ long_mode = (vcpu_vendor_get_efer() & EFER_LMA) &&
+ (cs_attr & VCPU_CS_L);
+
+ if (long_mode)
+ /* CS.d is ignored in long mode */
+ return has_opsz_prefix ? 2 : 4;
+
+ return (!!(cs_attr & VCPU_CS_DB) ^ has_opsz_prefix) ? 4 : 2;
+}
+
struct mmio_instruction
x86_mmio_parse(const struct guest_paging_structures *pg_structs, bool
is_write)
{
@@ -94,6 +114,7 @@ x86_mmio_parse(const struct guest_paging_structures
*pg_structs, bool is_write)
bool has_rex_w = false;
bool has_rex_r = false;
bool has_addrsz_prefix = false;
+ bool has_opsz_prefix = false;
if (!ctx_update(&ctx, &pc, 0, pg_structs))
goto error_noinst;
@@ -114,9 +135,13 @@ restart:
}
switch (op[0].raw) {
case X86_PREFIX_ADDR_SZ:
+ case X86_PREFIX_OP_SZ:
if (!ctx_update(&ctx, &pc, 1, pg_structs))
goto error_noinst;
- has_addrsz_prefix = true;
+ if (op[0].raw == X86_PREFIX_ADDR_SZ)
+ has_addrsz_prefix = true;
+ else
+ has_opsz_prefix = true;
goto restart;
case X86_OP_MOVZX_OPC1:
if (!ctx_update(&ctx, &pc, 1, pg_structs))
@@ -134,28 +159,28 @@ restart:
does_write = true;
break;
case X86_OP_MOV_TO_MEM:
- inst.access_size = has_rex_w ? 8 : 4;
+ inst.access_size = get_op_width(has_rex_w, has_opsz_prefix);
does_write = true;
break;
case X86_OP_MOVB_FROM_MEM:
inst.access_size = 1;
break;
case X86_OP_MOV_FROM_MEM:
- inst.access_size = has_rex_w ? 8 : 4;
+ inst.access_size = get_op_width(has_rex_w, has_opsz_prefix);
break;
case X86_OP_MOV_IMMEDIATE_TO_MEM:
- inst.access_size = has_rex_w ? 8 : 4;
+ inst.access_size = get_op_width(has_rex_w, has_opsz_prefix);
has_immediate = true;
does_write = true;
break;
case X86_OP_MOV_MEM_TO_AX:
inst.inst_len += get_address_width(has_addrsz_prefix);
- inst.access_size = has_rex_w ? 8 : 4;
+ inst.access_size = get_op_width(has_rex_w, has_opsz_prefix);
inst.in_reg_num = 15;
goto final;
case X86_OP_MOV_AX_TO_MEM:
inst.inst_len += get_address_width(has_addrsz_prefix);
- inst.access_size = has_rex_w ? 8 : 4;
+ inst.access_size = get_op_width(has_rex_w, has_opsz_prefix);
inst.out_val = guest_regs->by_index[15];
does_write = true;
goto final;
diff --git a/inmates/tests/x86/mmio-access-32.c
b/inmates/tests/x86/mmio-access-32.c
index 2f47f211..b4f83850 100644
--- a/inmates/tests/x86/mmio-access-32.c
+++ b/inmates/tests/x86/mmio-access-32.c
@@ -41,6 +41,10 @@ void inmate_main(void)
mmio_write32(mmio_reg, pattern);
EXPECT_EQUAL(*comm_page_reg, pattern);
+ /* MOV_FROM_MEM (8b), 16-bit data, 32-bit address, OP size prefix */
+ asm volatile("mov (%%eax), %%ax" : "=a" (reg32) : "a" (mmio_reg));
+ EXPECT_EQUAL(reg32, (u16)pattern);
+
/* MOV_FROM_MEM (8b), 32-bit data, 32-bit address */
asm volatile("movl (%%ebx), %%eax"
: "=a" (reg32) : "a" (0), "b" (mmio_reg));
diff --git a/inmates/tests/x86/mmio-access.c b/inmates/tests/x86/mmio-access.c
index 0e6a56b1..86694353 100644
--- a/inmates/tests/x86/mmio-access.c
+++ b/inmates/tests/x86/mmio-access.c
@@ -51,6 +51,10 @@ void inmate_main(void)
mmio_write64(mmio_reg, pattern);
EXPECT_EQUAL(*comm_page_reg, pattern);
+ /* MOV_FROM_MEM (8b), 16-bit data, Ox66 OP size prefix */
+ asm volatile("mov (%%rax), %%ax" : "=a" (reg64) : "a" (mmio_reg));
+ EXPECT_EQUAL(reg64, (u16)pattern);
+
/* MOV_FROM_MEM (8b), 64-bit data, mod=0, reg=0, rm=3 */
asm volatile("movq (%%rbx), %%rax"
: "=a" (reg64) : "a" (0), "b" (mmio_reg));
