KVM: x86: Return error on cmpxchg16b emulation

cmpxchg16b is currently unimplemented in the emulator. The least we can do is
return error upon the emulation of this instruction.

Signed-off-by: Nadav Amit <namit@cs.technion.ac.il>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 4 insertions, 1 deletions

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 3da8d82acb31..a151f8d24a1d 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -1999,6 +1999,9 @@ static int em_cmpxchg8b(struct x86_emulate_ctxt *ctxt)
 {
         u64 old = ctxt->dst.orig_val64;
 
+        if (ctxt->dst.bytes == 16)
+                return X86EMUL_UNHANDLEABLE;
+
         if (((u32) (old >> 0) != (u32) reg_read(ctxt, VCPU_REGS_RAX)) ||
             ((u32) (old >> 32) != (u32) reg_read(ctxt, VCPU_REGS_RDX))) {
                 *reg_write(ctxt, VCPU_REGS_RAX) = (u32) (old >> 0);
@@ -4077,7 +4080,7 @@ static int decode_operand(struct x86_emulate_ctxt *ctxt, struct operand *op,
                 op->orig_val = op->val;
                 break;
         case OpMem64:
-                ctxt->memop.bytes = 8;
+                ctxt->memop.bytes = (ctxt->op_bytes == 8) ? 16 : 8;
                 goto mem_common;
         case OpAcc:
                 op->type = OP_REG;