Gleb Natapov wrote: > On Tue, Feb 16, 2010 at 11:37:15AM +0100, Jan Kiszka wrote: >> Gleb Natapov wrote: >>> On Tue, Feb 16, 2010 at 11:27:07AM +0100, Jan Kiszka wrote: >>>> Gleb Natapov wrote: >>>>> On Tue, Feb 16, 2010 at 11:14:45AM +0100, Jan Kiszka wrote: >>>>>> Gleb Natapov wrote: >>>>>>> On Tue, Feb 16, 2010 at 11:04:10AM +0100, Jan Kiszka wrote: >>>>>>>> Gleb Natapov wrote: >>>>>>>>> On Tue, Feb 16, 2010 at 10:16:12AM +0100, Jan Kiszka wrote: >>>>>>>>>> Found while browsing Xen code: While we assume that the STI interrupt >>>>>>>>>> shadow also inplies virtual NMI blocking, some processors may have a >>>>>>>>>> different opinion (SDM 3: 22.3). To avoid misunderstandings that would >>>>>>>>>> cause endless VM entry attempts, translate STI into MOV SS blocking when >>>>>>>>>> requesting the NMI window. >>>>>>>>>> >>>>>>>>> Why not just remove "block by STI" check in vmx_nmi_allowed()? IIRC this >>>>>>>>> is documented that on some CPUs STI does not block NMI. >>>>>>>>> >>>>>>>> Probably because we will stumble and fall on those CPUs that do care. >>>>>>>> >>>>>>> But this defines behaviour of cpu _we_ emulate. So on _our_ cpu NMI will >>>>>>> not be blocked by STI. >>>>>> The host CPU decides if it accepts an NMI injections while >>>>> Are you sure? I haven't found such check during VMENTRY. >>>> I also only find the explicitly stated exclusion of MOV SS blocking vs. >>>> NMI injection. If we can rely on this, removing STI blocking from >>>> vmx_nmi_allowed should suffice. Or, better, can we get an official >>>> confirmation from Intel? >>>> >>> SDM 2b says about STI instruction: >>> The IF flag and the STI and CLI instructions do not prohibit the >>> generation of exceptions and NMI interrupts. NMI interrupts (and SMIs) >>> may be blocked for one macroinstruction following an STI. >> Yes, it's likely that this is the architectural reason for the delayed >> NMI window signaling after STI. Still, we are looking for the >> entry-check logic. >> > Will ask Intel. > Just remembered that there was some open topic... Did your ask? Any answer? Jan -- Siemens AG, Corporate Technology, CT T DE IT 1 Corporate Competence Center Embedded Linux -- 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
