[PATCH] KVM: x86 emulator: fix handling for unemulated instructions

[PATCH] KVM: x86 emulator: fix handling for unemulated instructions

[Avi Kivity]

If an instruction is present in the decode tables but not in the execution
switch, it will be emulated as a NOP.  An example is IRET (0xcf).

Fix by adding default: labels to the execution switches.

Signed-off-by: Avi Kivity <avi@redhat.com>
---
 arch/x86/kvm/emulate.c |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index b38bd8b..a12512d 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -3029,6 +3029,8 @@ special_insn:
 		if (c->modrm_reg == 5)
 			goto jump_far;
 		goto grp45;
+	default:
+		goto cannot_emulate;
 	}
 
 writeback:
@@ -3354,6 +3356,8 @@ twobyte_insn:
 		if (rc != X86EMUL_CONTINUE)
 			goto done;
 		break;
+	default:
+		goto cannot_emulate;
 	}
 	goto writeback;
 
-- 
1.7.1

Re: [PATCH] KVM: x86 emulator: fix handling for unemulated instructions

[Marcelo Tosatti]

On Sun, Jul 25, 2010 at 02:51:16PM +0300, Avi Kivity wrote:
> If an instruction is present in the decode tables but not in the execution
> switch, it will be emulated as a NOP.  An example is IRET (0xcf).
> 
> Fix by adding default: labels to the execution switches.
> 
> Signed-off-by: Avi Kivity <avi@redhat.com>
> ---
>  arch/x86/kvm/emulate.c |    4 ++++
>  1 files changed, 4 insertions(+), 0 deletions(-)

Applied, thanks.