Re: [PATCH] selftests: kvm: Check whether SIDA memop fails for normal guests

[Thomas Huth]

On 15/02/2022 10.54, Janis Schoetterl-Glausch wrote:
> On 2/15/22 08:48, Thomas Huth wrote:
> > Commit 2c212e1baedc ("KVM: s390: Return error on SIDA memop on normal
> > guest") fixed the behavior of the SIDA memops for normal guests. It
> > would be nice to have a way to test whether the current kernel has
> > the fix applied or not. Thus add a check to the KVM selftests for
> > these two memops.
> >
> > Signed-off-by: Thomas Huth <thuth@xxxxxxxxxx>
> > ---
> >   tools/testing/selftests/kvm/s390x/memop.c | 15 +++++++++++++++
> >   1 file changed, 15 insertions(+)
> >
> > diff --git a/tools/testing/selftests/kvm/s390x/memop.c b/tools/testing/selftests/kvm/s390x/memop.c
> > index 9f49ead380ab..d19c3ffdea3f 100644
> > --- a/tools/testing/selftests/kvm/s390x/memop.c
> > +++ b/tools/testing/selftests/kvm/s390x/memop.c
> > @@ -160,6 +160,21 @@ int main(int argc, char *argv[])
> >   	run->psw_mask &= ~(3UL << (63 - 17));   /* Disable AR mode */
> >   	vcpu_run(vm, VCPU_ID);                  /* Run to sync new state */
> >
> > +	/* Check that the SIDA calls are rejected for non-protected guests */
> > +	ksmo.gaddr = 0;
> > +	ksmo.flags = 0;
> > +	ksmo.size = 8;
> > +	ksmo.op = KVM_S390_MEMOP_SIDA_READ;
> > +	ksmo.buf = (uintptr_t)mem1;
> > +	ksmo.sida_offset = 0x1c0;
>
> What is the rational for that constant?
> Any would do, as long as size + offset < PAGE_SIZE, correct?

Right, it's rather a random value.

 Thomas