Re: [PATCH] KVM: VMX: Translate interrupt shadow when waiting on NMI window

[Gleb Natapov <gleb@redhat.com>]

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.

> blocked-by-STI is set, not we. But, of course, we could also translate
> STI into MOV SS blocking unconditionally. Whatever is preferred.
> 

--
			Gleb.