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

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] The computed driver region size uses `getpagesize()` as the minimum instead of `SZ_2M`, contradicting the commit message and altering test behavior.
--

--- Patch [7]: [PATCH v3 07/11] vfio: selftests: Allow drivers to specify required region size ---
commit 1aaddaa801402ac0c163d72d8dfe6ba18a6b7295
Author: Jason Gunthorpe <jgg@ziepe.ca>

vfio: selftests: Allow drivers to specify required region size

Add a region_size field to struct vfio_pci_driver_ops to let drivers
declare their DMA-mapped region size requirements. The core code will
round up and minimize the size to avoid changing test behavior.

> diff --git a/tools/testing/selftests/vfio/lib/vfio_pci_driver.c b/tools/testing/selftests/vfio/lib/vfio_pci_driver.c
> index 6827f4a6febe9..e13bbb7ee423d 100644
> --- a/tools/testing/selftests/vfio/lib/vfio_pci_driver.c
> +++ b/tools/testing/selftests/vfio/lib/vfio_pci_driver.c

[ ... ]

> @@ -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());

[Severity: Medium]
The commit message mentions that the core code will "minimize it to SZ_2M
so as not to change any test behavior."

Does this code in vfio_pci_driver_probe() compute the minimum size correctly
by using getpagesize() instead of SZ_2M? This appears to shrink the allocated
DMA region size for existing test drivers down to the page size, which might
alter the test behavior the commit message intended to preserve.

>  	}
>  }

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/0-v3-76f117ad04f1+28a90-mlx5st_jgg@nvidia.com?part=7