KVM: x86 emulator: add decoding of CMPXCHG8B dst operand
Decode CMPXCHG8B destination operand in decoding stage. Fixes regression
introduced by "If LOCK prefix is used dest arg should be memory" commit.
This commit relies on dst operand be decoded at the beginning of an
instruction emulation.
Signed-off-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 48de4b8..b8ce538 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -52,6 +52,7 @@
#define DstMem (3<<1) /* Memory operand. */
#define DstAcc (4<<1) /* Destination Accumulator */
#define DstDI (5<<1) /* Destination is in ES:(E)DI */
+#define DstMem64 (6<<1) /* 64bit memory operand */
#define DstMask (7<<1)
/* Source operand type. */
#define SrcNone (0<<4) /* No source operand. */
@@ -360,7 +361,7 @@
DstMem | SrcImmByte | ModRM, DstMem | SrcImmByte | ModRM | Lock,
DstMem | SrcImmByte | ModRM | Lock, DstMem | SrcImmByte | ModRM | Lock,
[Group9*8] =
- 0, ImplicitOps | ModRM | Lock, 0, 0, 0, 0, 0, 0,
+ 0, DstMem64 | ModRM | Lock, 0, 0, 0, 0, 0, 0,
};
static u32 group2_table[] = {
@@ -1205,6 +1206,7 @@
c->twobyte && (c->b == 0xb6 || c->b == 0xb7));
break;
case DstMem:
+ case DstMem64:
if ((c->d & ModRM) && c->modrm_mod == 3) {
c->dst.bytes = (c->d & ByteOp) ? 1 : c->op_bytes;
c->dst.type = OP_REG;
@@ -1214,7 +1216,10 @@
}
c->dst.type = OP_MEM;
c->dst.ptr = (unsigned long *)c->modrm_ea;
- c->dst.bytes = (c->d & ByteOp) ? 1 : c->op_bytes;
+ if ((c->d & DstMask) == DstMem64)
+ c->dst.bytes = 8;
+ else
+ c->dst.bytes = (c->d & ByteOp) ? 1 : c->op_bytes;
c->dst.val = 0;
if (c->d & BitOp) {
unsigned long mask = ~(c->dst.bytes * 8 - 1);
@@ -1706,12 +1711,7 @@
struct x86_emulate_ops *ops)
{
struct decode_cache *c = &ctxt->decode;
- u64 old, new;
- int rc;
-
- rc = ops->read_emulated(c->modrm_ea, &old, 8, ctxt->vcpu);
- if (rc != X86EMUL_CONTINUE)
- return rc;
+ u64 old = c->dst.orig_val;
if (((u32) (old >> 0) != (u32) c->regs[VCPU_REGS_RAX]) ||
((u32) (old >> 32) != (u32) c->regs[VCPU_REGS_RDX])) {
@@ -1719,15 +1719,12 @@
c->regs[VCPU_REGS_RAX] = (u32) (old >> 0);
c->regs[VCPU_REGS_RDX] = (u32) (old >> 32);
ctxt->eflags &= ~EFLG_ZF;
-
} else {
- new = ((u64)c->regs[VCPU_REGS_RCX] << 32) |
+ c->dst.val = ((u64)c->regs[VCPU_REGS_RCX] << 32) |
(u32) c->regs[VCPU_REGS_RBX];
- rc = ops->cmpxchg_emulated(c->modrm_ea, &old, &new, 8, ctxt->vcpu);
- if (rc != X86EMUL_CONTINUE)
- return rc;
ctxt->eflags |= EFLG_ZF;
+ c->lock_prefix = 1;
}
return X86EMUL_CONTINUE;
}
@@ -3245,7 +3242,6 @@
rc = emulate_grp9(ctxt, ops);
if (rc != X86EMUL_CONTINUE)
goto done;
- c->dst.type = OP_NONE;
break;
}
goto writeback;