Re: [PATCH v3 07/11] vfio: selftests: Allow drivers to specify required region size

[David Matlack <dmatlack@google.com>]

On 2026-07-16 02:03 PM, 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. The core code will round up and minimize it to SZ_2M so as not to
> change any test behavior.

Please update this last sentence to match the patch.

> 
> Assisted-by: Claude:claude-opus-4.6
> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
> ---
>  tools/testing/selftests/vfio/lib/drivers/dsa/dsa.c         | 1 +
>  tools/testing/selftests/vfio/lib/drivers/ioat/ioat.c       | 1 +
>  .../selftests/vfio/lib/include/libvfio/vfio_pci_driver.h   | 6 ++++++
>  tools/testing/selftests/vfio/lib/vfio_pci_driver.c         | 7 +++++++
>  tools/testing/selftests/vfio/vfio_pci_driver_test.c        | 3 ++-
>  5 files changed, 17 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/testing/selftests/vfio/lib/drivers/dsa/dsa.c b/tools/testing/selftests/vfio/lib/drivers/dsa/dsa.c
> index 19d9630b24c23f..40b8541b588eee 100644
> --- a/tools/testing/selftests/vfio/lib/drivers/dsa/dsa.c
> +++ b/tools/testing/selftests/vfio/lib/drivers/dsa/dsa.c
> @@ -418,6 +418,7 @@ static void dsa_send_msi(struct vfio_pci_device *device)
>  
>  const struct vfio_pci_driver_ops dsa_ops = {
>  	.name = "dsa",
> +	.region_size = sizeof(struct dsa_state),
>  	.probe = dsa_probe,
>  	.init = dsa_init,
>  	.remove = dsa_remove,
> diff --git a/tools/testing/selftests/vfio/lib/drivers/ioat/ioat.c b/tools/testing/selftests/vfio/lib/drivers/ioat/ioat.c
> index a871b935542bad..c9b28365c5eb6b 100644
> --- a/tools/testing/selftests/vfio/lib/drivers/ioat/ioat.c
> +++ b/tools/testing/selftests/vfio/lib/drivers/ioat/ioat.c
> @@ -226,6 +226,7 @@ static void ioat_send_msi(struct vfio_pci_device *device)
>  
>  const struct vfio_pci_driver_ops ioat_ops = {
>  	.name = "ioat",
> +	.region_size = sizeof(struct ioat_state),

When you rebase on top of vfio/next please also make these changes to
the NV Falcon and IGB drivers that have recently landed.

>  	.probe = ioat_probe,
>  	.init = ioat_init,
>  	.remove = ioat_remove,
> diff --git a/tools/testing/selftests/vfio/lib/include/libvfio/vfio_pci_driver.h b/tools/testing/selftests/vfio/lib/include/libvfio/vfio_pci_driver.h
> index e5ada209b1d102..547369c5cff95a 100644
> --- a/tools/testing/selftests/vfio/lib/include/libvfio/vfio_pci_driver.h
> +++ b/tools/testing/selftests/vfio/lib/include/libvfio/vfio_pci_driver.h
> @@ -9,6 +9,12 @@ struct vfio_pci_device;
>  struct vfio_pci_driver_ops {
>  	const char *name;
>  
> +	/*
> +	 * Size of the driver's state structure overlaid on
> +	 * device->driver.region.vaddr
> +	 */
> +	u64 region_size;
> +
>  	/**
>  	 * @probe() - Check if the driver supports the given device.
>  	 *
> diff --git a/tools/testing/selftests/vfio/lib/vfio_pci_driver.c b/tools/testing/selftests/vfio/lib/vfio_pci_driver.c
> index 6827f4a6febe99..e13bbb7ee423dc 100644
> --- a/tools/testing/selftests/vfio/lib/vfio_pci_driver.c
> +++ b/tools/testing/selftests/vfio/lib/vfio_pci_driver.c
> @@ -1,5 +1,7 @@
>  // SPDX-License-Identifier: GPL-2.0-only
>  #include "kselftest.h"
> +#include <linux/sizes.h>
> +#include <linux/log2.h>
>  #include <libvfio.h>
>  
>  #ifdef __x86_64__
> @@ -28,6 +30,11 @@ 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 =
> +			max_t(u64, roundup_pow_of_two(ops->region_size),
> +			      getpagesize());

Blegh this is because the IOVA allocator insists on a power-of-2 size as
you pointed out [1]. Can you add a comment here to document that? Or
better yet, move the rounding up into iova_allocator_alloc() so the
callers don't have to deal with it like this.

[1] https://lore.kernel.org/all/20260529173753.GB128816@nvidia.com/

>  	}
>  }
>  
> diff --git a/tools/testing/selftests/vfio/vfio_pci_driver_test.c b/tools/testing/selftests/vfio/vfio_pci_driver_test.c
> index afa0480ddd9b2a..f68239da574f5a 100644
> --- a/tools/testing/selftests/vfio/vfio_pci_driver_test.c
> +++ b/tools/testing/selftests/vfio/vfio_pci_driver_test.c
> @@ -80,7 +80,8 @@ FIXTURE_SETUP(vfio_pci_driver_test)
>  	driver = &self->device->driver;
>  
>  	region_setup(self->iommu, self->iova_allocator, &self->memcpy_region, SZ_1G);
> -	region_setup(self->iommu, self->iova_allocator, &driver->region, SZ_2M);
> +	region_setup(self->iommu, self->iova_allocator, &driver->region,
> +		     driver->region.size);
>  
>  	/* Any IOVA that doesn't overlap memcpy_region and driver->region. */
>  	self->unmapped_iova = iova_allocator_alloc(self->iova_allocator, SZ_1G);
> -- 
> 2.43.0
>