Re: [PATCH v5 07/21] KVM: selftests: Verify IRQ bypass works in IRQ test

[Sean Christopherson <seanjc@google.com>]

On Thu, Jun 04, 2026, Sean Christopherson wrote:
> On Thu, Jun 04, 2026, Sean Christopherson wrote:
> > diff --git tools/testing/selftests/kvm/irq_test.c tools/testing/selftests/kvm/irq_test.c
> > index cf4568718cee..2e7e100d4815 100644
> > --- tools/testing/selftests/kvm/irq_test.c
> > +++ tools/testing/selftests/kvm/irq_test.c
> > @@ -235,6 +235,8 @@ int main(int argc, char **argv)
> >         }
> >  
> >         if (device_bdf) {
> > +               __open_path_or_exit("/dev/iommu", O_RDONLY, "Is IOMMUFD available?");
> > +
> >                 iommu = iommu_init(default_iommu_mode);
> 
> *sigh* 
> 
> <rant>
> This is beyond frustating.  I have A PERFECTLY FUNCTIONAL KERNEL, but this test
> VERY SUBTLY "defaults" to IOMMUFD.  ARGH!!!!!
> 
> And to make matters worse, if I enable CONFIG_IOMMUFD, but don't enable
> CONFIG_VFIO_DEVICE_CDEV, then AFAICT, I can't do a damn thing with VFIO.  I dunno,
> I can't get IOMMUFD to work even with that.
> 
> Worst of all, the changelog SAYS BLOODY NOTHING ABOUT THIS.
> </rant>

Turns out the DSA SPR device is on VFIO's naughty list:

  vfio-pci 0000:6a:01.0: 8086:0b25 exists in vfio-pci device denylist, driver probing disallowed.
  vfio-pci 0000:6a:01.0: probe with driver vfio-pci failed with error -22

Reloading vfio-pci with disable_denylist=1 got things working.