Re: [PATCH 07/24] KVM: x86 emulator: fix 0f 01 /5 emulation

[Gleb Natapov <gleb@redhat.com>]

On Tue, Mar 09, 2010 at 04:27:39PM +0200, Avi Kivity wrote:
> On 03/09/2010 04:09 PM, Gleb Natapov wrote:
> >It is undefined and should generate #UD.
> >
> >Signed-off-by: Gleb Natapov<gleb@redhat.com>
> >---
> >  arch/x86/kvm/emulate.c |    3 +++
> >  1 files changed, 3 insertions(+), 0 deletions(-)
> >
> >diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
> >index 2df510b..1a32b78 100644
> >--- a/arch/x86/kvm/emulate.c
> >+++ b/arch/x86/kvm/emulate.c
> >@@ -2486,6 +2486,9 @@ twobyte_insn:
> >  				    (c->src.val&  0x0f), ctxt->vcpu);
> >  			c->dst.type = OP_NONE;
> >  			break;
> >+		case 5: /* not defined */
> >+			kvm_queue_exception(ctxt->vcpu, UD_VECTOR);
> >+			goto done;
> >  		case 7: /* invlpg*/
> >  			emulate_invlpg(ctxt->vcpu, memop);
> >  			/* Disable writeback. */
> 
> Why is this needed?  We can only get here if the guest tricks us
> (otherwise the #UD would go back to the guest, or rather, we'd trap
> it to see if it's a hypercall instruction, but not pass it on to the
> emulator).
> 
For completes. A lot of code we added recently is there only because guest
can trick us to enter emulator. Unfortunately we have to take suck tricks
into account. Without this patch if emulator gets here it will report failed
emulation.

--
			Gleb.