Re: [PATCH v6 06/10] vfio: selftests: Allow drivers to specify required region size

[David Matlack <dmatlack@google.com>]

On 2026-09-18 05:00 PM, Jason Gunthorpe wrote:
> On Fri, Sep 18, 2026 at 07:58:58AM -0700, David Matlack wrote:
> > > >
> > > > [Severity: Medium]
> > > > Since this changes the vfio test to use the dynamic driver->region.size
> > > > instead of SZ_2M, should tools/testing/selftests/kvm/irq_test.c be updated
> > > > as well?
> > > >
> > > > It looks like vfio_setup_msi() in kvm/irq_test.c still forcefully overwrites
> > > > the dynamically probed size back to 2MB:
> > > >
> > > > tools/testing/selftests/kvm/irq_test.c:vfio_setup_msi() {
> > > >       ...
> > > >       region = &device->driver.region;
> > > >       region->size = SZ_2M;
> > > >       region->iova = iova_allocator_alloc(allocator, region->size);
> > > >       ...
> > > > }
> > > >
> > > > Will this cause the KVM irq_test to fail with a VFIO_ASSERT_GE during driver
> > > > initialization via vfio_pci_driver_init() when tested with a driver that
> > > > requires a larger region, such as the mlx5 driver mentioned in the commit
> > > > message?
> > >
> > > I have no idea, Dave? Did kvm start using this stuff?
> > 
> > Yes, KVM started linking in the VFIO selftests library in 7.3 and
> > irq_test.c is the first test using it.
> 
> Okay, so I think this is all that is needed:
> 
> @@ -101,7 +100,6 @@ static int vfio_setup_msi(struct vfio_pci_device *device)
>         allocator = iova_allocator_init(device->iommu);
>  
>         region = &device->driver.region;
> -       region->size = SZ_2M;
>         region->iova = iova_allocator_alloc(allocator, region->size);
>         region->vaddr = kvm_mmap(region->size, prot, flags, -1);
>         TEST_ASSERT(region->vaddr != MAP_FAILED, "mmap() failed\n");
> 
> > Looks like that is also causing the dma_rmb/wmb() redefinition
> > compiler warning from the kernel-test-robot.
> 
> Yeah, for some reason kvm defined them in its private headers instead
> of putting them in the right place :(
> 
> I think I can just delete the kvm definitions.
> 
> I don't have an arm system or userspace cross compiler to test it with
> though..

Wait, really? I can help with building and running the KVM/arm64
selftests if that's what you need.

> Are we good on everything else, can Alex pick it up after I fix this?

Yes all good from my pov after we address this feedback. I am no longer
seeing failures[1] when using the IGB driver with this series applied.

[1] https://lore.kernel.org/all/anzvkibgzTae9eV9@google.com/