Re: [PATCH 3/4] vfio: selftests: add iova allocator

[Alex Williamson <alex@shazbot.org>]

On Mon, 10 Nov 2025 13:10:43 -0800
Alex Mastro <amastro@fb.com> wrote:

> Add struct iova_allocator, which gives tests a convenient way to generate
> legally-accessible IOVAs to map.
> 
> This is based on Alex Williamson's patch series for adding an IOVA
> allocator [1].
> 
> [1] https://lore.kernel.org/all/20251108212954.26477-1-alex@shazbot.org/
> 
> Signed-off-by: Alex Mastro <amastro@fb.com>
> ---
>  .../testing/selftests/vfio/lib/include/vfio_util.h | 14 +++++
>  tools/testing/selftests/vfio/lib/vfio_pci_device.c | 65 +++++++++++++++++++++-
>  2 files changed, 78 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/testing/selftests/vfio/lib/include/vfio_util.h b/tools/testing/selftests/vfio/lib/include/vfio_util.h
> index fb5efec52316..bb1e7d39dfb9 100644
> --- a/tools/testing/selftests/vfio/lib/include/vfio_util.h
> +++ b/tools/testing/selftests/vfio/lib/include/vfio_util.h
> @@ -13,6 +13,8 @@
>  
>  #include "../../../kselftest.h"
>  
> +#define ALIGN(x, a)	(((x) + (a - 1)) & (~((a) - 1)))
> +
>  #define VFIO_LOG_AND_EXIT(...) do {		\
>  	fprintf(stderr, "  " __VA_ARGS__);	\
>  	fprintf(stderr, "\n");			\
> @@ -188,6 +190,13 @@ struct vfio_pci_device {
>  	struct vfio_pci_driver driver;
>  };
>  
> +struct iova_allocator {
> +	struct iommu_iova_range *ranges;
> +	size_t nranges;
> +	size_t range_idx;
> +	iova_t iova_next;
> +};
> +
>  /*
>   * Return the BDF string of the device that the test should use.
>   *
> @@ -212,6 +221,11 @@ void vfio_pci_device_reset(struct vfio_pci_device *device);
>  struct iommu_iova_range *vfio_pci_iova_ranges(struct vfio_pci_device *device,
>  					      size_t *nranges);
>  
> +int iova_allocator_init(struct vfio_pci_device *device,
> +			    struct iova_allocator *allocator);
> +void iova_allocator_deinit(struct iova_allocator *allocator);
> +iova_t iova_allocator_alloc(struct iova_allocator *allocator, size_t size);
> +
>  int __vfio_pci_dma_map(struct vfio_pci_device *device,
>  		       struct vfio_dma_region *region);
>  int __vfio_pci_dma_unmap(struct vfio_pci_device *device,
> diff --git a/tools/testing/selftests/vfio/lib/vfio_pci_device.c b/tools/testing/selftests/vfio/lib/vfio_pci_device.c
> index 6bedbe65f0a1..a634feb1d378 100644
> --- a/tools/testing/selftests/vfio/lib/vfio_pci_device.c
> +++ b/tools/testing/selftests/vfio/lib/vfio_pci_device.c
> @@ -12,11 +12,12 @@
>  #include <sys/mman.h>
>  
>  #include <uapi/linux/types.h>
> +#include <linux/iommufd.h>
>  #include <linux/limits.h>
>  #include <linux/mman.h>
> +#include <linux/overflow.h>
>  #include <linux/types.h>
>  #include <linux/vfio.h>
> -#include <linux/iommufd.h>
>  
>  #include "../../../kselftest.h"
>  #include <vfio_util.h>
> @@ -190,6 +191,68 @@ struct iommu_iova_range *vfio_pci_iova_ranges(struct vfio_pci_device *device,
>  	return ranges;
>  }
>  
> +int iova_allocator_init(struct vfio_pci_device *device,
> +			struct iova_allocator *allocator)
> +{
> +	struct iommu_iova_range *ranges;
> +	size_t nranges;
> +
> +	memset(allocator, 0, sizeof(*allocator));
> +
> +	ranges = vfio_pci_iova_ranges(device, &nranges);
> +	if (!ranges)
> +		return -ENOENT;
> +
> +	*allocator = (struct iova_allocator){
> +		.ranges = ranges,
> +		.nranges = nranges,
> +		.range_idx = 0,
> +		.iova_next = 0,

iova_next needs to be initialized from ranges[0].start.  Thanks,

Alex

> +	};
> +
> +	return 0;
> +}
> +
> +void iova_allocator_deinit(struct iova_allocator *allocator)
> +{
> +	free(allocator->ranges);
> +}
> +
> +iova_t iova_allocator_alloc(struct iova_allocator *allocator, size_t size)
> +{
> +	int idx = allocator->range_idx;
> +	struct iommu_iova_range *range = &allocator->ranges[idx];
> +
> +	VFIO_ASSERT_LT(idx, allocator->nranges, "IOVA allocator out of space\n");
> +	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");
> +
> +	for (;;) {
> +		iova_t iova, last;
> +
> +		iova = ALIGN(allocator->iova_next, size);
> +
> +		if (iova < allocator->iova_next || iova > range->last ||
> +		    check_add_overflow(iova, size - 1, &last) ||
> +		    last > range->last) {
> +			allocator->range_idx = ++idx;
> +			VFIO_ASSERT_LT(idx, allocator->nranges,
> +				       "Out of ranges for allocation\n");
> +			allocator->iova_next = (++range)->start;
> +			continue;
> +		}
> +
> +		if (check_add_overflow(last, (iova_t)1, &allocator->iova_next) ||
> +		    allocator->iova_next > range->last) {
> +			allocator->range_idx = ++idx;
> +			if (idx < allocator->nranges)
> +				allocator->iova_next = (++range)->start;
> +		}
> +
> +		return iova;
> +	}
> +}
> +
>  iova_t __to_iova(struct vfio_pci_device *device, void *vaddr)
>  {
>  	struct vfio_dma_region *region;
>