[PATCH v1] KVM: arm64: selftests: Test pointer authentication support in KVM guest

[Jing Zhang]

Hi Oliver,

On Wed, Aug 2, 2023 at 1:17 PM Oliver Upton <oliver.upton at linux.dev> wrote:
>
> Hi Jing,
>
> Nothing serious, but when you're replying on a thread can you add a
> leading and trailing line of whitespace between the quotation and your
> reply? Otherwise threads get really dense and hard to read.

Will do. Thanks for the suggestion.

>
> On Wed, Aug 02, 2023 at 10:19:30AM -0700, Jing Zhang wrote:
> > > > +                     case FAIL_KVM:
> > > > +                             TEST_FAIL("KVM doesn't support guest PAuth!\n");
> > >
> > > Why is that a hard failure? The vast majority of the HW out there
> > > doesn't support PAuth...
> > Since previous TEST_REQUIRES have passed, KVM should be able to
> > support guest PAuth. The test will be skipped on those HW without
> > PAuth.
>
> So then what is the purpose of this failure mode? The only case where
> this would happen is if KVM is if KVM screwed up the emulation somehow,
> took a trap on a PAC instruction or register and reflected that back
> into the guest as an UNDEF.

You are right about the purpose of this test case.

>
> That's a perfectly valid thing to test for, but the naming and failure
> messages should indicate what actually happened.

Sure. Will use more sensible messages.

>
> > > As I mentioned above, another thing I'd like to see is a set of
> > > reference results for a given set of keys and architected algorithm
> > > (QARMA3, QARMA5) so that we can compare between implementations
> > > (excluding the IMPDEF implementations, of course).
> > Sure. Will do.
>
> I was initially hesitant towards testing PAC like this since it is
> entirely a hardware issue besides KVM context switching, but you could
> spin this off as a way to test if vCPU save/restore works correctly by
> priming the vCPU from userspace.
>
> Marc, is there something else here you're interested in exercising I
> may've missed?
>
> --
> Thanks,
> Oliver

Thanks,
Jing