> > > > + if (!eax_0 ||
> > > > + ((ebx_0 & INTEL_PT_MINIMAL_EBX) != INTEL_PT_MINIMAL_EBX) ||
> > > > + ((ecx_0 & INTEL_PT_MINIMAL_ECX) != INTEL_PT_MINIMAL_ECX) ||
> > > > + ((eax_1 & INTEL_PT_MTC_BITMAP) != INTEL_PT_MTC_BITMAP) ||
> > > > + ((eax_1 & INTEL_PT_ADDR_RANGES_NUM_MASK) <
> > > > + INTEL_PT_ADDR_RANGES_NUM) ||
> > > > + ((ebx_1 & (INTEL_PT_PSB_BITMAP | INTEL_PT_CYCLE_BITMAP)) !=
> > > > + (INTEL_PT_PSB_BITMAP | INTEL_PT_CYCLE_BITMAP))) {
> > >
> > > I still don't see a check to ensure the host has bit 31 on ecx_0 set to 0, as I mentioned when reviewing v3.
> >
> > Hi Eduardo,
> > Thanks for the code review. I don't quite understand here why
> > bit31 must same with host (meaning we must reject a host where ecx_0 & (1 << 31) is set).
>
> If the guest sees the bit set to 0, it will expect IP payloads with RIP values, but the host CPU will generate IP payloads with LIP values.
> I assume KVM won't do RIP<->LIP translation on the packets generated by the host before the guest sees them, will it?
Fully understand. Will make a separate patch on this.
Thanks,
Luwei Kang
>
>
> > Do you mean PT must be disabled in guest when host bit31 is set?
> > Bit 31: If 1, generated packets which contain IP payloads have LIP values, which include the CS base component.
> > I can't find any special on this bit. Could you help clarify?
>
> As far as I understand, this bit is special because KVM can't emulate a value that's different from the host.
>
> --
> Eduardo
