linux-kernel - [PATCH 3/4] vfio: selftests: add iova allocator

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Message-ID: <20251110-iova-ranges-v1-3-4d441cf5bf6d@fb.com>
Date: Mon, 10 Nov 2025 13:10:43 -0800
From: Alex Mastro <amastro@...com>
To: Alex Williamson <alex@...zbot.org>, David Matlack <dmatlack@...gle.com>,
        Shuah Khan <shuah@...nel.org>
CC: <kvm@...r.kernel.org>, <linux-kselftest@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, Alex Mastro <amastro@...com>,
        Jason Gunthorpe
	<jgg@...pe.ca>
Subject: [PATCH 3/4] vfio: selftests: add iova allocator

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,
+	};
+
+	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;

-- 
2.47.3