linux-kernel - Re: [PATCH 2/4] vfio: selftests: fix map limit tests to use last available iova

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Message-ID: <20251110143152.5af498f4.alex@shazbot.org>
Date: Mon, 10 Nov 2025 14:31:52 -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 2/4] vfio: selftests: fix map limit tests to use last
 available iova

On Mon, 10 Nov 2025 13:10:42 -0800
Alex Mastro <amastro@...com> wrote:

> Use the newly available vfio_pci_iova_ranges() to determine the last
> legal IOVA, and use this as the basis for vfio_dma_map_limit_test tests.
> 
> Fixes: de8d1f2fd5a5 ("vfio: selftests: add end of address space DMA map/unmap tests")
> Signed-off-by: Alex Mastro <amastro@...com>
> ---
>  tools/testing/selftests/vfio/vfio_dma_mapping_test.c | 17 +++++++++++++++--
>  1 file changed, 15 insertions(+), 2 deletions(-)
> 
> diff --git a/tools/testing/selftests/vfio/vfio_dma_mapping_test.c b/tools/testing/selftests/vfio/vfio_dma_mapping_test.c
> index 4f1ea79a200c..37c2a342df8d 100644
> --- a/tools/testing/selftests/vfio/vfio_dma_mapping_test.c
> +++ b/tools/testing/selftests/vfio/vfio_dma_mapping_test.c
> @@ -3,6 +3,8 @@
>  #include <sys/mman.h>
>  #include <unistd.h>
>  
> +#include <uapi/linux/types.h>
> +#include <linux/iommufd.h>
>  #include <linux/limits.h>
>  #include <linux/mman.h>
>  #include <linux/sizes.h>
> @@ -219,7 +221,10 @@ FIXTURE_VARIANT_ADD_ALL_IOMMU_MODES();
>  FIXTURE_SETUP(vfio_dma_map_limit_test)
>  {
>  	struct vfio_dma_region *region = &self->region;
> +	struct iommu_iova_range *ranges;
>  	u64 region_size = getpagesize();
> +	iova_t last_iova;
> +	size_t nranges;
>  
>  	/*
>  	 * Over-allocate mmap by double the size to provide enough backing vaddr
> @@ -232,8 +237,13 @@ FIXTURE_SETUP(vfio_dma_map_limit_test)
>  			     MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
>  	ASSERT_NE(region->vaddr, MAP_FAILED);
>  
> -	/* One page prior to the end of address space */
> -	region->iova = ~(iova_t)0 & ~(region_size - 1);
> +	ranges = vfio_pci_iova_ranges(self->device, &nranges);
> +	VFIO_ASSERT_NOT_NULL(ranges);
> +	last_iova = ranges[nranges - 1].last;


Building on the imposed requirement of ordered ranges.  Thanks,

Alex


> +	free(ranges);
> +
> +	/* One page prior to the last iova */
> +	region->iova = last_iova & ~(region_size - 1);
>  	region->size = region_size;
>  }
>  
> @@ -276,6 +286,9 @@ TEST_F(vfio_dma_map_limit_test, overflow)
>  	struct vfio_dma_region *region = &self->region;
>  	int rc;
>  
> +	if (region->iova != (~(iova_t)0 & ~(region->size - 1)))
> +		SKIP(return, "IOMMU address space insufficient for overflow test");
> +
>  	region->size = self->mmap_size;
>  
>  	rc = __vfio_pci_dma_map(self->device, region);
>