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Message-ID: <20251110143154.3ff4aa09.alex@shazbot.org>
Date: Mon, 10 Nov 2025 14:31:54 -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 3/4] vfio: selftests: add iova allocator
On Mon, 10 Nov 2025 13:10:43 -0800
Alex Mastro <amastro@...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@...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;
>
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