2014-12-03 09:04+0100, Paolo Bonzini:
> On 03/12/2014 00:05, Radim Krčmář wrote:
> > 2014-12-02 14:09+0100, Paolo Bonzini:
> >> + } else {
> >> + if (entry[i].eax == 0 || !(supported & mask))
> >> + continue;
> >> + WARN_ON_ONCE(entry[i].ecx & 1);
> >> + entry[i].ecx &= 1;
> >
> > ECX Bit 0 is set if the sub-leaf index, n, maps to a valid bit in the
> > IA32_XSS MSR and bit 0 is clear if n maps to a valid bit in XCR0.
> >
> > ECX should be set to 0 instead, we definitely don't map to a valid bit
> > in IA32_XSS now.
>
> Well, there is a WARN just above. :) But I can change it to zero instead.
Yeah, I wasn't sure about the WARN ... I can only see it trigger after
host xcr0 changes and we are much more screwed in that case anyway :)
(But it has a chance of catching a bug, so it isn't only bad.)
The guest expects 0 here, so I'd rather have it ...
> > (Having only one part of cpuid ready for it is weird ...)
> >
> >> + }
> >> + entry[i].edx = 0;
> >> entry[i].flags |=
> >> KVM_CPUID_FLAG_SIGNIFCANT_INDEX;
> >
> > (Unrelated, I have yet to understand how this flag translates
> > * If ECX contains an invalid sub-leaf index, EAX/EBX/ECX/EDX return 0.)
>
> If the index is invalid, entry[i].eax is zero and we do not return
> anything at all.
I see, the field is sparse and "++*nent; ++i;", not the flag, does it,
thanks.
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