[COMMIT master] KVM: x86 emulator: If LOCK prefix is used dest arg should be memory.

[Avi Kivity]

From: Gleb Natapov <g...@redhat.com>

If LOCK prefix is used dest arg should be memory, otherwise instruction
should generate #UD.

Signed-off-by: Gleb Natapov <g...@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosa...@redhat.com>

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index b89a8f2..46a7ee3 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -1842,7 +1842,7 @@ x86_emulate_insn(struct x86_emulate_ctxt *ctxt, struct 
x86_emulate_ops *ops)
        }
 
        /* LOCK prefix is allowed only with some instructions */
-       if (c->lock_prefix && !(c->d & Lock)) {
+       if (c->lock_prefix && (!(c->d & Lock) || c->dst.type != OP_MEM)) {
                kvm_queue_exception(ctxt->vcpu, UD_VECTOR);
                goto done;
        }
--
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