From mboxrd@z Thu Jan  1 00:00:00 1970
From: Gleb Natapov <gleb@redhat.com>
Subject: Re: [PATCH 2/2] x86: Bail out on unemulated instructions
Date: Sun, 15 Aug 2010 15:41:12 +0300
Message-ID: <20100815124112.GR10499@redhat.com>
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To: Mohammed Gamal <m.gamal005@gmail.com>
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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> wrot=
e:
> > 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 exe=
cute 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 r=
eal
> > 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
>=20
That doesn't makes the patch right. So we will have to figure something
out.

> >
> >> Signed-off-by: Mohammed Gamal <m.gamal005@gmail.com>
> >> ---
> >> =9Aarch/x86/kvm/x86.c | =9A =9A6 ++++++
> >> =9A1 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 *vcp=
u,
> >> =9A =9A =9A =9A =9A =9A =9A }
> >>
> >> =9A =9A =9A =9A =9A =9A =9A ++vcpu->stat.insn_emulation;
> >> + =9A =9A =9A =9A =9A =9A if (r =3D=3D X86EMUL_UNHANDLEABLE)
> >> + =9A =9A =9A =9A =9A =9A =9A =9A =9A =9A return handle_emulation_=
failure(vcpu);
> >> +
> >> =9A =9A =9A =9A =9A =9A =9A if (r) =9A{
> >> =9A =9A =9A =9A =9A =9A =9A =9A =9A =9A =9A if (reexecute_instruct=
ion(vcpu, cr2))
> >> =9A =9A =9A =9A =9A =9A =9A =9A =9A =9A =9A =9A =9A =9A =9A return=
 EMULATE_DONE;
> >> @@ -4057,6 +4060,9 @@ int emulate_instruction(struct kvm_vcpu *vcp=
u,
> >> =9Arestart:
> >> =9A =9A =9A r =3D x86_emulate_insn(&vcpu->arch.emulate_ctxt);
> >>
> >> + =9A =9A if (r =3D=3D X86EMUL_UNHANDLEABLE)
> >> + =9A =9A =9A =9A =9A =9A return handle_emulation_failure(vcpu);
> >> +
> >> =9A =9A =9A if (r) { /* emulation failed */
> >> =9A =9A =9A =9A =9A =9A =9A if (reexecute_instruction(vcpu, cr2))
> >> =9A =9A =9A =9A =9A =9A =9A =9A =9A =9A =9A return EMULATE_DONE;
> >> --
> >> 1.7.0.4
> >>
> >> --
> >> To unsubscribe from this list: send the line "unsubscribe kvm" in
> >> the body of a message to majordomo@vger.kernel.org
> >> More majordomo info at =9Ahttp://vger.kernel.org/majordomo-info.ht=
ml
> >
> > --
> > =9A =9A =9A =9A =9A =9A =9A =9A =9A =9A =9A =9AGleb.
> >

--
			Gleb.