Re: [PATCH v3 6/9] KVM: x86: Untag LAM bits when applicable

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OBOn Wed, Dec 21, 2022 at 06:22:47PM +0800, Yu Zhang wrote:
> > > >
> > > > IIUC, LAM_47 userspace canonical checking rule requests "bit 63 ==
> > > > bit 47 == 0"
> > > > before sign-extened the address.
> > > >
> > > > if so looks it's guest's fault to not follow the LAM canonical
> > > > checking rule,
> > > > what's the behavior of such violation on bare metal, #GP ?
> > >
> > > Spec (ISE 10.2) doesn't mention a #GP for this case. IIUC, those
> > > overlap bits are zeroed.
> >
> > I mean the behavior of violation of "bit 63 == bit 47 == 0" rule,
> > yes no words in ISE 10.2/3 describe the behavior of such violation
> > case, but do you know more details of this or had some experiments
> > on hardware/SIMIC ?
>
> Yes, the ISE is vague. But I do believe a #GP will be generated for
> such violation, and KVM shall inject one if guest does no follow the
> requirement, because such check is called(by the spec) as a "modified
> canonicality check".

Me too and that's why I had replies here :-)

>
> Anyway, we'd better confirm with the spec owner, instead of making
> assumptions by ourselves. :)

Agree!

>
> B.R.
> Yu



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