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Message-ID: <20260113-map-mmio-test-v2-3-e6d34f09c0bb@fb.com>
Date: Tue, 13 Jan 2026 15:08:38 -0800
From: Alex Mastro <amastro@...com>
To: Alex Williamson <alex@...zbot.org>, David Matlack <dmatlack@...gle.com>,
Shuah Khan <shuah@...nel.org>
CC: Peter Xu <peterx@...hat.com>, <linux-kernel@...r.kernel.org>,
<kvm@...r.kernel.org>, <linux-kselftest@...r.kernel.org>,
Jason Gunthorpe
<jgg@...pe.ca>, Alex Mastro <amastro@...com>
Subject: [PATCH v2 3/3] vfio: selftests: Add vfio_dma_mapping_mmio_test
Test IOMMU mapping the BAR mmaps created during vfio_pci_device_setup().
All IOMMU modes are tested: vfio_type1 variants are expected to succeed,
while non-type1 modes are expected to fail. iommufd compat mode can be
updated to expect success once kernel support lands; native iommufd will
not support mapping vaddrs backed by MMIO (it will support dma-buf based
MMIO mapping instead).
Signed-off-by: Alex Mastro <amastro@...com>
---
tools/testing/selftests/vfio/Makefile | 1 +
.../selftests/vfio/vfio_dma_mapping_mmio_test.c | 144 +++++++++++++++++++++
2 files changed, 145 insertions(+)
diff --git a/tools/testing/selftests/vfio/Makefile b/tools/testing/selftests/vfio/Makefile
index 3c796ca99a50..ead27892ab65 100644
--- a/tools/testing/selftests/vfio/Makefile
+++ b/tools/testing/selftests/vfio/Makefile
@@ -1,5 +1,6 @@
CFLAGS = $(KHDR_INCLUDES)
TEST_GEN_PROGS += vfio_dma_mapping_test
+TEST_GEN_PROGS += vfio_dma_mapping_mmio_test
TEST_GEN_PROGS += vfio_iommufd_setup_test
TEST_GEN_PROGS += vfio_pci_device_test
TEST_GEN_PROGS += vfio_pci_device_init_perf_test
diff --git a/tools/testing/selftests/vfio/vfio_dma_mapping_mmio_test.c b/tools/testing/selftests/vfio/vfio_dma_mapping_mmio_test.c
new file mode 100644
index 000000000000..5a86b34329ad
--- /dev/null
+++ b/tools/testing/selftests/vfio/vfio_dma_mapping_mmio_test.c
@@ -0,0 +1,144 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#include <stdio.h>
+#include <sys/mman.h>
+#include <unistd.h>
+
+#include <uapi/linux/types.h>
+#include <linux/pci_regs.h>
+#include <linux/sizes.h>
+#include <linux/vfio.h>
+
+#include <libvfio.h>
+
+#include "../kselftest_harness.h"
+
+static const char *device_bdf;
+
+static struct vfio_pci_bar *largest_mapped_bar(struct vfio_pci_device *device)
+{
+ u32 flags = VFIO_REGION_INFO_FLAG_READ | VFIO_REGION_INFO_FLAG_WRITE;
+ struct vfio_pci_bar *largest = NULL;
+ u64 bar_size = 0;
+
+ for (int i = 0; i < PCI_STD_NUM_BARS; i++) {
+ struct vfio_pci_bar *bar = &device->bars[i];
+
+ if (!bar->vaddr)
+ continue;
+
+ /*
+ * iommu_map() maps with READ|WRITE, so require the same
+ * abilities for the underlying VFIO region.
+ */
+ if ((bar->info.flags & flags) != flags)
+ continue;
+
+ if (bar->info.size > bar_size) {
+ bar_size = bar->info.size;
+ largest = bar;
+ }
+ }
+
+ return largest;
+}
+
+FIXTURE(vfio_dma_mapping_mmio_test) {
+ struct iommu *iommu;
+ struct vfio_pci_device *device;
+ struct iova_allocator *iova_allocator;
+ struct vfio_pci_bar *bar;
+};
+
+FIXTURE_VARIANT(vfio_dma_mapping_mmio_test) {
+ const char *iommu_mode;
+};
+
+#define FIXTURE_VARIANT_ADD_IOMMU_MODE(_iommu_mode) \
+FIXTURE_VARIANT_ADD(vfio_dma_mapping_mmio_test, _iommu_mode) { \
+ .iommu_mode = #_iommu_mode, \
+}
+
+FIXTURE_VARIANT_ADD_ALL_IOMMU_MODES();
+
+#undef FIXTURE_VARIANT_ADD_IOMMU_MODE
+
+FIXTURE_SETUP(vfio_dma_mapping_mmio_test)
+{
+ self->iommu = iommu_init(variant->iommu_mode);
+ self->device = vfio_pci_device_init(device_bdf, self->iommu);
+ self->iova_allocator = iova_allocator_init(self->iommu);
+ self->bar = largest_mapped_bar(self->device);
+
+ if (!self->bar)
+ SKIP(return, "No mappable BAR found on device %s", device_bdf);
+
+ if (self->bar->info.size < 2 * getpagesize())
+ SKIP(return, "BAR too small (size=0x%llx)", self->bar->info.size);
+}
+
+FIXTURE_TEARDOWN(vfio_dma_mapping_mmio_test)
+{
+ iova_allocator_cleanup(self->iova_allocator);
+ vfio_pci_device_cleanup(self->device);
+ iommu_cleanup(self->iommu);
+}
+
+static void do_mmio_map_test(struct iommu *iommu,
+ struct iova_allocator *iova_allocator,
+ void *vaddr, size_t size)
+{
+ struct dma_region region = {
+ .vaddr = vaddr,
+ .size = size,
+ .iova = iova_allocator_alloc(iova_allocator, size),
+ };
+
+ /*
+ * NOTE: Check for iommufd compat success once it lands. Native iommufd
+ * will never support this.
+ */
+ if (!strcmp(iommu->mode->name, MODE_VFIO_TYPE1V2_IOMMU) ||
+ !strcmp(iommu->mode->name, MODE_VFIO_TYPE1_IOMMU)) {
+ iommu_map(iommu, ®ion);
+ iommu_unmap(iommu, ®ion);
+ } else {
+ VFIO_ASSERT_NE(__iommu_map(iommu, ®ion), 0);
+ VFIO_ASSERT_NE(__iommu_unmap(iommu, ®ion, NULL), 0);
+ }
+}
+
+TEST_F(vfio_dma_mapping_mmio_test, map_full_bar)
+{
+ do_mmio_map_test(self->iommu, self->iova_allocator,
+ self->bar->vaddr, self->bar->info.size);
+}
+
+TEST_F(vfio_dma_mapping_mmio_test, map_partial_bar)
+{
+ do_mmio_map_test(self->iommu, self->iova_allocator,
+ self->bar->vaddr, getpagesize());
+}
+
+/* Test IOMMU mapping of BAR mmap with intentionally poor vaddr alignment. */
+TEST_F(vfio_dma_mapping_mmio_test, map_bar_misaligned)
+{
+ /* Limit size to bound test time for large BARs */
+ size_t size = min_t(size_t, self->bar->info.size, SZ_1G);
+ size_t page_size = getpagesize();
+ void *vaddr;
+
+ vaddr = mmap_aligned(size, SZ_1G, page_size);
+ vaddr = mmap(vaddr, size, PROT_READ | PROT_WRITE, MAP_SHARED | MAP_FIXED,
+ self->device->fd, self->bar->info.offset);
+ VFIO_ASSERT_NE(vaddr, MAP_FAILED);
+
+ do_mmio_map_test(self->iommu, self->iova_allocator, vaddr, size);
+
+ VFIO_ASSERT_EQ(munmap(vaddr, size), 0);
+}
+
+int main(int argc, char *argv[])
+{
+ device_bdf = vfio_selftests_get_bdf(&argc, argv);
+ return test_harness_run(argc, argv);
+}
--
2.47.3
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