Re: [PATCH 2/2] x86: Bail out on unemulated instructions

[Gleb Natapov <gleb@redhat.com>]

On Sun, Aug 15, 2010 at 03:40:00PM +0300, Mohammed Gamal wrote:
> On Sun, Aug 15, 2010 at 10:32 AM, Gleb Natapov <gleb@redhat.com> wrote:
> > On Sat, Aug 14, 2010 at 06:51:34PM +0300, Mohammed Gamal wrote:
> >> If emulation fails due to the instruction being unemulated. Return immediately
> >> instead of restarting the instruction and infinitely trying to execute it.
> >>
> > This is already handled correctly as far as I can see. Sometimes
> > instruction should be retried and reexecute_instruction() checks
> > for that case. If instruction emulation fails in big real mode
> > re-executing instruction will be useless though, so what should be done
> > is to make reexecute_instruction() return false if vcpu is in big real
> > mode and cpu relies on emulation to handle it.
> We don't have a separate mode for big real mode. The emulation modes
> we have are real and vm86
> 
That doesn't makes the patch right. So we will have to figure something
out.

> >
> >> Signed-off-by: Mohammed Gamal <m.gamal005@gmail.com>
> >> ---
> >>  arch/x86/kvm/x86.c |    6 ++++++
> >>  1 files changed, 6 insertions(+), 0 deletions(-)
> >>
> >> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> >> index 416aa0e..a31db44 100644
> >> --- a/arch/x86/kvm/x86.c
> >> +++ b/arch/x86/kvm/x86.c
> >> @@ -4036,6 +4036,9 @@ int emulate_instruction(struct kvm_vcpu *vcpu,
> >>               }
> >>
> >>               ++vcpu->stat.insn_emulation;
> >> +             if (r == X86EMUL_UNHANDLEABLE)
> >> +                     return handle_emulation_failure(vcpu);
> >> +
> >>               if (r)  {
> >>                       if (reexecute_instruction(vcpu, cr2))
> >>                               return EMULATE_DONE;
> >> @@ -4057,6 +4060,9 @@ int emulate_instruction(struct kvm_vcpu *vcpu,
> >>  restart:
> >>       r = x86_emulate_insn(&vcpu->arch.emulate_ctxt);
> >>
> >> +     if (r == X86EMUL_UNHANDLEABLE)
> >> +             return handle_emulation_failure(vcpu);
> >> +
> >>       if (r) { /* emulation failed */
> >>               if (reexecute_instruction(vcpu, cr2))
> >>                       return EMULATE_DONE;
> >> --
> >> 1.7.0.4
> >>
> >> --
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> >
> > --
> >                        Gleb.
> >

--
			Gleb.