linux-kernel - Re: [PATCH 4/4] vfio: selftests: update vfio_dma_mapping

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Message-ID: <20251110143156.08d1859b.alex@shazbot.org>
Date: Mon, 10 Nov 2025 14:31:56 -0700
From: Alex Williamson <alex@...zbot.org>
To: Alex Mastro <amastro@...com>
Cc: David Matlack <dmatlack@...gle.com>, Shuah Khan <shuah@...nel.org>,
 <kvm@...r.kernel.org>, <linux-kselftest@...r.kernel.org>,
 <linux-kernel@...r.kernel.org>, Jason Gunthorpe <jgg@...pe.ca>
Subject: Re: [PATCH 4/4] vfio: selftests: update vfio_dma_mapping_test to
 allocate iovas

On Mon, 10 Nov 2025 13:10:44 -0800
Alex Mastro <amastro@...com> wrote:

> vfio_dma_mapping_test currently uses iova=vaddr as part of DMA mapping
> validation. The assumption that these IOVAs are legal has held up on all
> the hardware we've tested so far, but but is not guaranteed. Make the
> test more robust by using iova_allocator to vend IOVAs, which queries
> legally accessible IOVAs from the underlying IOMMUFD or VFIO container.
> 
> Signed-off-by: Alex Mastro <amastro@...com>
> ---
>  tools/testing/selftests/vfio/vfio_dma_mapping_test.c | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/testing/selftests/vfio/vfio_dma_mapping_test.c b/tools/testing/selftests/vfio/vfio_dma_mapping_test.c
> index 37c2a342df8d..c1a015385b0f 100644
> --- a/tools/testing/selftests/vfio/vfio_dma_mapping_test.c
> +++ b/tools/testing/selftests/vfio/vfio_dma_mapping_test.c
> @@ -95,6 +95,7 @@ static int iommu_mapping_get(const char *bdf, u64 iova,
>  
>  FIXTURE(vfio_dma_mapping_test) {
>  	struct vfio_pci_device *device;
> +	struct iova_allocator iova_allocator;
>  };
>  
>  FIXTURE_VARIANT(vfio_dma_mapping_test) {
> @@ -118,11 +119,16 @@ FIXTURE_VARIANT_ADD_ALL_IOMMU_MODES(anonymous_hugetlb_1gb, SZ_1G, MAP_HUGETLB |
>  
>  FIXTURE_SETUP(vfio_dma_mapping_test)
>  {
> +	int ret;
> +
>  	self->device = vfio_pci_device_init(device_bdf, variant->iommu_mode);
> +	ret = iova_allocator_init(self->device, &self->iova_allocator);
> +	VFIO_ASSERT_EQ(ret, 0);
>  }
>  
>  FIXTURE_TEARDOWN(vfio_dma_mapping_test)
>  {
> +	iova_allocator_deinit(&self->iova_allocator);
>  	vfio_pci_device_cleanup(self->device);
>  }
>  
> @@ -144,7 +150,7 @@ TEST_F(vfio_dma_mapping_test, dma_map_unmap)
>  	else
>  		ASSERT_NE(region.vaddr, MAP_FAILED);
>  
> -	region.iova = (u64)region.vaddr;
> +	region.iova = iova_allocator_alloc(&self->iova_allocator, size);
>  	region.size = size;
>  
>  	vfio_pci_dma_map(self->device, &region);
> 

There's another in the driver test.  Thanks,

Alex