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@fb.com>
Reviewed-by: David Matlack <dmatlack@google.com>
Tested-by: David Matlack <dmatlack@google.com>
Link: https://lore.kernel.org/r/20260114-map-mmio-test-v3-3-44e036d95e64@fb.com
Signed-off-by: Alex Williamson <alex@shazbot.org>

Author: Alex Mastro

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

tools/testing/selftests/vfio/vfio_dma_mapping_mmio_test.c

@@ -0,0 +1,143 @@
+// 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);
+}
+
+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, &region);
+		iommu_unmap(iommu, &region);
+	} else {
+		VFIO_ASSERT_NE(__iommu_map(iommu, &region), 0);
+		VFIO_ASSERT_NE(__iommu_unmap(iommu, &region, 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)
+{
+	if (self->bar->info.size < 2 * getpagesize())
+		SKIP(return, "BAR too small (size=0x%llx)", self->bar->info.size);
+
+	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);
+	void *vaddr;
+
+	vaddr = mmap_reserve(size, SZ_1G, getpagesize());
+	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);
+}