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

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2010/8/15 Gleb Natapov <gleb@xxxxxxxxxx>:
> 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@xxxxxxxxxx> 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.
True. Can we do it for real mode in general (i.e. X86EMUL_MODE_REAL)?
>
>> >
>> >> Signed-off-by: Mohammed Gamal <m.gamal005@xxxxxxxxx>
>> >> ---
>> >>  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
>> >>
>> >> --
>> >> To unsubscribe from this list: send the line "unsubscribe kvm" in
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>> >
>> > --
>> >                        Gleb.
>> >
>
> --
>                        Gleb.
>
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