Re: [PATCH v4 5/5] vfio: selftests: Allow a size for vfio_dma_mapping_perf_test

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential
issue to consider:
- [Low] vfio: selftests: non-power-of-2 -b size aborts in
  iova_allocator_alloc()
--

commit 7eb32375cc90a8bc43da0741f8174df52036eeb6
Author: Aaron Lewis <aaronlewis@google.com>

vfio: selftests: Allow a size for vfio_dma_mapping_perf_test

This commit adds a '-b' command-line option to vfio_dma_mapping_perf_test to
allow specifying the DMA region size to map and unmap.

> diff --git a/tools/testing/selftests/vfio/vfio_dma_mapping_perf_test.c b/tools/testing/selftests/vfio/vfio_dma_mapping_perf_test.c
> index 086a63a50df80..6e38cc134a49c 100644
> --- a/tools/testing/selftests/vfio/vfio_dma_mapping_perf_test.c
> +++ b/tools/testing/selftests/vfio/vfio_dma_mapping_perf_test.c

[ ... ]

> @@ -58,11 +136,16 @@ FIXTURE_TEARDOWN(vfio_dma_mapping_perf_test)
>  
>  TEST_F(vfio_dma_mapping_perf_test, dma_map_unmap)
>  {
> -	const u64 size = SZ_1G;
> +	const u64 page_size = variant->page_size ?: getpagesize();
> +	const u64 size = test_params.size;
>  	const int flags = variant->mmap_flags;
>  	struct dma_region region;
>  
> -	ksft_print_msg("mmap size = %lluG\n", (unsigned long long)(size / SZ_1G));
> +	if (!IS_ALIGNED(size, page_size))
> +		SKIP(return, "Size 0x%llx is not aligned to page size 0x%llx",
> +		     (unsigned long long)size, (unsigned long long)page_size);
> +
> +	ksft_print_msg("mmap size = %s\n", test_params.size_str);
>  
>  	TIME("mmap",
>  	     region.vaddr = mmap(NULL, size, PROT_READ | PROT_WRITE, flags, -1, 0));

[Severity: Low]
Will passing a non-power-of-2 size such as "-b 3G" abort the test inside
iova_allocator_alloc()?

parse_size() accepts any positive multiplier and both dma_map_unmap and
dma_map_unmap_from_file only check IS_ALIGNED(size, page_size), but after
populating the mapping they pass size directly to iova_allocator_alloc(),
which requires a power of two:

tools/testing/selftests/vfio/lib/iova_allocator.c:iova_allocator_alloc() {
	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");
    ...
}

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20261114132200.113697-1-aaronlewis@google.com?part=5