On Sun, Aug 01, 2010 at 01:00:11PM +0300, Avi Kivity wrote: > On 08/01/2010 12:24 PM, Gleb Natapov wrote: > >On Sun, Aug 01, 2010 at 12:14:40PM +0300, Avi Kivity wrote: > >> On 08/01/2010 12:01 PM, Gleb Natapov wrote: > >>>>>It uses rip _during_ pio. And pio emulation changes rip > >>>>>only at the end of emulation. > >>>>But non-emulated pio does a skip_emulated_instruction() immediately > >>>>(or so the code in kvm-tpr-opt.c assumes: > >>>> > >>>Indeed, this is bug in non-emulated pio. > >>But userspace depends on this bug. > >We can fix that, or make it smarter. Look for io instruction at > >rip/rip-2 and use rip accordingly for instance. > > That requires everyone to update, or suffer major breakage. > They will suffer major breakage when they update to a kvm that calls to kvm-tpr-opt.c from emulator anyway. > >>>But the patch does not change > >>>rip behaviour for emulated pio. vcpu->arch.emulate_ctxt.eip is updated > >>>only at the end of emulation. > >>That will lead to failures if the emulator is used for the > >>kvm-tpr-opt pio (which may happen with big real mode). > >> > >IIRC it was always this way in emulator. I'd rather fix userspace than > >break emulator. > > It wasn't a problem because the emulator wasn't (and still isn't) > used for this. But it has the potential to break badly once we make > emulate_invalid_guest_state=1 the default. > So what can we do about it? -- Gleb. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
