vfio: selftests: add iova allocator

Add struct iova_allocator, which gives tests a convenient way to generate
legally-accessible IOVAs to map. This allocator traverses the sorted
available IOVA ranges linearly, requires power-of-two size allocations,
and does not support freeing iova allocations. The assumption is that
tests are not IOVA space-bounded, and will not need to recycle IOVAs.

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/

Reviewed-by: David Matlack <dmatlack@google.com>
Tested-by: David Matlack <dmatlack@google.com>
Signed-off-by: Alex Mastro <amastro@fb.com>
Link: https://lore.kernel.org/r/20251111-iova-ranges-v3-3-7960244642c5@fb.com
Signed-off-by: Alex Williamson <alex@shazbot.org>

diff --git a/tools/testing/selftests/vfio/lib/include/vfio_util.h b/tools/testing/selftests/vfio/lib/include/vfio_util.h
index ef8f06ef0c1390ab0a886706009a281a48b64ef7..69ec0c85648106e90536b908bddde94101623aa1 100644 (file)
--- a/tools/testing/selftests/vfio/lib/include/vfio_util.h
+++ b/tools/testing/selftests/vfio/lib/include/vfio_util.h
@@ -188,6 +188,13 @@ struct vfio_pci_device {
        struct vfio_pci_driver driver;
 };
 
+struct iova_allocator {
+       struct iommu_iova_range *ranges;
+       u32 nranges;
+       u32 range_idx;
+       u64 range_offset;
+};
+
 /*
  * Return the BDF string of the device that the test should use.
  *
@@ -212,6 +219,10 @@ void vfio_pci_device_reset(struct vfio_pci_device *device);
 struct iommu_iova_range *vfio_pci_iova_ranges(struct vfio_pci_device *device,
                                              u32 *nranges);
 
+struct iova_allocator *iova_allocator_init(struct vfio_pci_device *device);
+void iova_allocator_cleanup(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 11749348f53fa6cded326932d1cfaf4a93dea997..b479a359da121c4c884c84b5617aa3f4e40b80b3 100644 (file)
--- 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>
@@ -201,6 +202,77 @@ struct iommu_iova_range *vfio_pci_iova_ranges(struct vfio_pci_device *device,
        return ranges;
 }
 
+struct iova_allocator *iova_allocator_init(struct vfio_pci_device *device)
+{
+       struct iova_allocator *allocator;
+       struct iommu_iova_range *ranges;
+       u32 nranges;
+
+       ranges = vfio_pci_iova_ranges(device, &nranges);
+       VFIO_ASSERT_NOT_NULL(ranges);
+
+       allocator = malloc(sizeof(*allocator));
+       VFIO_ASSERT_NOT_NULL(allocator);
+
+       *allocator = (struct iova_allocator){
+               .ranges = ranges,
+               .nranges = nranges,
+               .range_idx = 0,
+               .range_offset = 0,
+       };
+
+       return allocator;
+}
+
+void iova_allocator_cleanup(struct iova_allocator *allocator)
+{
+       free(allocator->ranges);
+       free(allocator);
+}
+
+iova_t iova_allocator_alloc(struct iova_allocator *allocator, size_t size)
+{
+       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 (;;) {
+               struct iommu_iova_range *range;
+               iova_t iova, last;
+
+               VFIO_ASSERT_LT(allocator->range_idx, allocator->nranges,
+                              "IOVA allocator out of space\n");
+
+               range = &allocator->ranges[allocator->range_idx];
+               iova = range->start + allocator->range_offset;
+
+               /* Check for sufficient space at the current offset */
+               if (check_add_overflow(iova, size - 1, &last) ||
+                   last > range->last)
+                       goto next_range;
+
+               /* Align iova to size */
+               iova = last & ~(size - 1);
+
+               /* Check for sufficient space at the aligned iova */
+               if (check_add_overflow(iova, size - 1, &last) ||
+                   last > range->last)
+                       goto next_range;
+
+               if (last == range->last) {
+                       allocator->range_idx++;
+                       allocator->range_offset = 0;
+               } else {
+                       allocator->range_offset = last - range->start + 1;
+               }
+
+               return iova;
+
+next_range:
+               allocator->range_idx++;
+               allocator->range_offset = 0;
+       }
+}
+
 iova_t __to_iova(struct vfio_pci_device *device, void *vaddr)
 {
        struct vfio_dma_region *region;