Re: [PATCH v4 06/10] vfio: selftests: Allow drivers to specify required region size

On Wed, Aug 12, 2026 at 3:11 PM David Matlack <[email protected]> wrote:
>
> On 2026-08-12 11:59 AM, Jason Gunthorpe wrote:
> > Add a region_size field to struct vfio_pci_driver_ops so drivers can
> > declare how much DMA-mapped region they need. The mlx5 driver will need
> > ~18MB for firmware pages. Existing drivers pass in the sizeof their state
> > struct. Since drivers all use only their declared state we can use the
> > value directly and remove the SZ_2M hard coding.
> >
> > Assisted-by: Claude:claude-opus-4.6
> > Signed-off-by: Jason Gunthorpe <[email protected]>
>
> ...
>
> > diff --git a/tools/testing/selftests/vfio/lib/iova_allocator.c b/tools/testing/selftests/vfio/lib/iova_allocator.c
> > index 4a660f636f4972..c8075575e9131d 100644
> > --- a/tools/testing/selftests/vfio/lib/iova_allocator.c
> > +++ b/tools/testing/selftests/vfio/lib/iova_allocator.c
> > @@ -13,8 +13,10 @@
> >
> >  #include <linux/iommufd.h>
> >  #include <linux/limits.h>
> > +#include <linux/log2.h>
> >  #include <linux/mman.h>
> >  #include <linux/overflow.h>
> > +#include <linux/sizes.h>
> >  #include <linux/types.h>
> >  #include <linux/vfio.h>
> >
> > @@ -50,7 +52,8 @@ void iova_allocator_cleanup(struct iova_allocator *allocator)
> >  iova_t iova_allocator_alloc(struct iova_allocator *allocator, size_t size)
> >  {
> >       VFIO_ASSERT_GT(size, 0, "Invalid size arg, zero\n");
> > -     VFIO_ASSERT_EQ(size & (size - 1), 0, "Invalid size arg, non-power-of-2\n");
> > +     /* Adjust the size to the allocator requirements */
> > +     size = max_t(u64, roundup_pow_of_two(size), getpagesize());
>
> ...
>
> > diff --git a/tools/testing/selftests/vfio/lib/vfio_pci_driver.c b/tools/testing/selftests/vfio/lib/vfio_pci_driver.c
> > index 5e65434d2318b2..52b9c2a2bbb9b6 100644
> > --- a/tools/testing/selftests/vfio/lib/vfio_pci_driver.c
> > +++ b/tools/testing/selftests/vfio/lib/vfio_pci_driver.c
> > @@ -32,6 +32,9 @@ void vfio_pci_driver_probe(struct vfio_pci_device *device)
> >                       continue;
> >
> >               device->driver.ops = ops;
> > +
> > +             VFIO_ASSERT_NE(ops->region_size, 0);
> > +             device->driver.region.size = ops->region_size;
>
> I'm seeing failures with the IGB driver with this series. I think it's
> coming from here. The region size needs to be page-aligned so that the
> IOMMU map/unmap calls can work?
>
> The size of struct igb is 0x20080 bytes which is not page-aligned. The
> size of struct mlx5st_device is 0x200D000, which is page-aligned, so
> that's probably why your Claude did not notice.
>
> # #  RUN           vfio_pci_driver_test.iommufd.send_msi ...
> # /usr/local/google/home/dmatlack/kernel/trees/review/tools/testing/selftests/vfio/lib/include/libvfio/iommu.h:42:
> # Assertion Failure
> #
> #   Expression: __iommu_map(iommu, region) == 0
> #   Observed: 0xffffffffffffffea == 0
> #   [errno: 22 - Invalid argument]
> #
> # # send_msi: Test failed
> # #          FAIL  vfio_pci_driver_test.iommufd.send_msi
> # not ok 33 vfio_pci_driver_test.iommufd.send_msi
>
> Applying this on top fixes things and also avoids a potential overflow
> when doing the roundup_pow_of_two() in the allocator.
>
> diff --git a/tools/testing/selftests/vfio/lib/iova_allocator.c b/tools/testing/selftests/vfio/lib/iova_allocator.c
> index c8075575e913..66a160d4ff9d 100644
> --- a/tools/testing/selftests/vfio/lib/iova_allocator.c
> +++ b/tools/testing/selftests/vfio/lib/iova_allocator.c
> @@ -52,8 +52,11 @@ void iova_allocator_cleanup(struct iova_allocator *allocator)
>  iova_t iova_allocator_alloc(struct iova_allocator *allocator, size_t size)
>  {
>         VFIO_ASSERT_GT(size, 0, "Invalid size arg, zero\n");
> -       /* Adjust the size to the allocator requirements */
> -       size = max_t(u64, roundup_pow_of_two(size), getpagesize());
> +       VFIO_ASSERT_LT(size, rounddown_pow_of_two(SIZE_MAX),

Oops, that should be VFIO_ASSERT_LE().

> +                      "Invalid size arg, too large (%lu)\n", size);
> +
> +       size = roundup_pow_of_two(size);
>
>         for (;;) {
>                 struct iommu_iova_range *range;
> diff --git a/tools/testing/selftests/vfio/lib/vfio_pci_driver.c b/tools/testing/selftests/vfio/lib/vfio_pci_driver.c
> index 96a940ea59b5..b31abfe2c7ff 100644
> --- a/tools/testing/selftests/vfio/lib/vfio_pci_driver.c
> +++ b/tools/testing/selftests/vfio/lib/vfio_pci_driver.c
> @@ -36,7 +36,8 @@ void vfio_pci_driver_probe(struct vfio_pci_device *device)
>                 device->driver.ops = ops;
>
>                 VFIO_ASSERT_NE(ops->region_size, 0);
> -               device->driver.region.size = ops->region_size;
> +               device->driver.region.size =
> +                       round_up(ops->region_size, getpagesize());
>         }
>  }