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

[David Matlack <dmatlack@google.com>]

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 <jgg@nvidia.com>

...

> 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),
+		       "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());
 	}
 }