Re: [PATCH v3 16/30] KVM: x86 emulator: If LOCK prefix is used dest arg should be memory.

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Gleb Natapov wrote:
If LOCK prefix is used dest arg should be memory, otherwise instruction
should generate #UD.
Well, there is one exception:
There is an AMD specific "lock mov cr0 = mov cr8" equivalence, where there is no memory involved (and we intercept this). I am not sure if anyone actually uses this code sequence, but it is definitely legal.

Regards,
Andre.


Signed-off-by: Gleb Natapov <gleb@xxxxxxxxxx>
---
 arch/x86/kvm/emulate.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

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;
 	}


--
Andre Przywara
AMD-OSRC (Dresden)
Tel: x29712

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