On Fri, Sep 24, 2021 at 12:09:06AM +0000, Sean Christopherson wrote:
> On Thu, Sep 23, 2021, Oliver Upton wrote:
> > While x86 does not require any additional setup to use the ucall
> > infrastructure, arm64 needs to set up the MMIO address used to signal a
> > ucall to userspace. rseq_test does not initialize the MMIO address,
> > resulting in the test spinning indefinitely.
> >
> > Fix the issue by calling ucall_init() during setup.
> >
> > Fixes: 61e52f1630f5 ("KVM: selftests: Add a test for KVM_RUN+rseq to detect task migration bugs")
> > Signed-off-by: Oliver Upton <oupton@xxxxxxxxxx>
> > ---
> > tools/testing/selftests/kvm/rseq_test.c | 1 +
> > 1 file changed, 1 insertion(+)
> >
> > diff --git a/tools/testing/selftests/kvm/rseq_test.c b/tools/testing/selftests/kvm/rseq_test.c
> > index 060538bd405a..c5e0dd664a7b 100644
> > --- a/tools/testing/selftests/kvm/rseq_test.c
> > +++ b/tools/testing/selftests/kvm/rseq_test.c
> > @@ -180,6 +180,7 @@ int main(int argc, char *argv[])
> > * CPU affinity.
> > */
> > vm = vm_create_default(VCPU_ID, 0, guest_code);
> > + ucall_init(vm, NULL);
>
> Any reason not to do this automatically in vm_create()? There is 0% chance I'm
> going to remember to add this next time I write a common selftest, arm64 is the
> oddball here.
>
Yes, please. But, it'll take more than just adding a ucall_init(vm, NULL)
call to vm_create. We should also modify aarch64's ucall_init to allow
a *new* explicit mapping to be made. It already allows an explicit mapping
when arg != NULL, but we'll need to unmap the default mapping first, now.
The reason is that a unit test may not be happy with the automatically
selected address (that hasn't happened yet, but...) and want to set its
own.
Thanks,
drew
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