Subject: Re: [PATCH v2 07/11] vfio: selftests: Allow drivers to specify required region size

From: David Matlack <[email-masked]>
Date: Thu, 28 May 2026 18:59:38 +0000

On 2026-05-15 02:30 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.
> 
> Assisted-by: Claude:claude-opus-4.6
> Signed-off-by: Jason Gunthorpe <[email-masked]>
> ---
>  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/vfio_pci_driver_test.c        | 7 ++++++-
>  4 files changed, 14 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),
>  	.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/vfio_pci_driver_test.c b/tools/testing/selftests/vfio/vfio_pci_driver_test.c
> index afa0480ddd9b2a..5a46800cde4c8d 100644
> --- a/tools/testing/selftests/vfio/vfio_pci_driver_test.c
> +++ b/tools/testing/selftests/vfio/vfio_pci_driver_test.c
> @@ -2,6 +2,7 @@
>  #include <sys/ioctl.h>
>  #include <sys/mman.h>
>  
> +#include <linux/log2.h>
>  #include <linux/sizes.h>
>  #include <linux/vfio.h>
>  
> @@ -80,7 +81,11 @@ 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);
> +
> +	VFIO_ASSERT_NE(driver->ops->region_size, 0);
> +	region_setup(self->iommu, self->iova_allocator, &driver->region,
> +		     max_t(u64, roundup_pow_of_two(driver->ops->region_size),
> +			   SZ_2M));

We have some other upcoming tests that want to set up the driver region, so it
would be nice to move this into the library.

  * https://lore.kernel.org/kvm/[email-masked]/
  * https://lore.kernel.org/kvm/[email-masked]/

What about something like this?

diff --git a/tools/testing/selftests/vfio/lib/drivers/dsa/dsa.c b/tools/testing/selftests/vfio/lib/drivers/dsa/dsa.c
index 19d9630b24c2..40b8541b588e 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 a871b935542b..c9b28365c5eb 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),
        .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 e5ada209b1d1..547369c5cff9 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 6827f4a6febe..c70c22b1a86c 100644
--- a/tools/testing/selftests/vfio/lib/vfio_pci_driver.c
+++ b/tools/testing/selftests/vfio/lib/vfio_pci_driver.c
@@ -28,6 +28,9 @@ 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 = roundup(ops->region_size, getpagesize());
        }
 }

diff --git a/tools/testing/selftests/vfio/vfio_pci_driver_test.c b/tools/testing/selftests/vfio/vfio_pci_driver_test.c
index afa0480ddd9b..36d977542274 100644
--- a/tools/testing/selftests/vfio/vfio_pci_driver_test.c
+++ b/tools/testing/selftests/vfio/vfio_pci_driver_test.c
@@ -80,7 +80,7 @@ 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);

>  
>  	/* 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
>