Commit 3a6095a0 authored Aug 13, 2014 by Nadav Amit Committed by Paolo Bonzini Aug 19, 2014

KVM: x86: Avoid emulating instructions on #UD mistakenly



Commit d40a6898 mistakenly caused instructions which are not marked as
EmulateOnUD to be emulated upon #UD exception. The commit caused the check of
whether the instruction flags include EmulateOnUD to never be evaluated. As a
result instructions whose emulation is broken may be emulated.  This fix moves
the evaluation of EmulateOnUD so it would be evaluated.

Signed-off-by: Nadav Amit <namit@cs.technion.ac.il>
[Tweak operand order in &&, remove EmulateOnUD where it's now superfluous.
 - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

parent c04fa583

arch/x86/kvm/emulate.c

+4 −4

Original line number	Diff line number	Diff line
		@@ -4394,8 +4394,11 @@ done_prefixes:

		ctxt->execute = opcode.u.execute;

		if (unlikely(ctxt->ud) && likely(!(ctxt->d & EmulateOnUD)))
		return EMULATION_FAILED;

		if (unlikely(ctxt->d &
		(NotImpl\|EmulateOnUD\|Stack\|Op3264\|Sse\|Mmx\|Intercept\|CheckPerm))) {
		(NotImpl\|Stack\|Op3264\|Sse\|Mmx\|Intercept\|CheckPerm))) {
		/*
		* These are copied unconditionally here, and checked unconditionally
		* in x86_emulate_insn.
		@@ -4406,9 +4409,6 @@ done_prefixes:
		if (ctxt->d & NotImpl)
		return EMULATION_FAILED;

		if (!(ctxt->d & EmulateOnUD) && ctxt->ud)
		return EMULATION_FAILED;

		if (mode == X86EMUL_MODE_PROT64 && (ctxt->d & Stack))
		ctxt->op_bytes = 8;