On 2026-01-07 02:13 PM, Alex Mastro wrote: > Test MMIO-backed DMA mappings by iommu_map()-ing mmap'ed BAR regions.
Thanks for adding this! > Also update vfio_pci_bar_map() to align BAR mmaps for efficient huge > page mappings. > > Only vfio_type1 variants are tested; iommufd variants can be added > once kernel support lands. Are there plans to support mapping BARs via virtual address in iommufd? I thought the plan was only to support via dma-bufs. Maybe Jason can confirm. Assuming not, should we add negative tests here to make sure iommufd does not allow mapping BARs? And then we can add dma-buf tests in a future commit. > The manual mmap alignment can be removed > once mmap(!MAP_FIXED) on vfio device fds improves to automatically > return well-aligned addresses. > > Signed-off-by: Alex Mastro <[email protected]> > --- > Sanity test run: > > $ ./vfio_dma_mapping_mmio_test 0000:05:00.0 > TAP version 13 > 1..4 > # Starting 4 tests from 2 test cases. > # RUN vfio_dma_mapping_mmio_test.vfio_type1_iommu.map_full_bar ... > Mapping BAR4: vaddr=0x7fad40000000 size=0x2000000000 iova=0x2000000000 > # OK vfio_dma_mapping_mmio_test.vfio_type1_iommu.map_full_bar > ok 1 vfio_dma_mapping_mmio_test.vfio_type1_iommu.map_full_bar > # RUN vfio_dma_mapping_mmio_test.vfio_type1_iommu.map_partial_bar > ... > Mapping BAR4 (partial): vaddr=0x7fad40000000 size=0x1000 iova=0x0 > # OK vfio_dma_mapping_mmio_test.vfio_type1_iommu.map_partial_bar > ok 2 vfio_dma_mapping_mmio_test.vfio_type1_iommu.map_partial_bar > # RUN vfio_dma_mapping_mmio_test.vfio_type1v2_iommu.map_full_bar > ... > Mapping BAR4: vaddr=0x7fad40000000 size=0x2000000000 iova=0x2000000000 > # OK vfio_dma_mapping_mmio_test.vfio_type1v2_iommu.map_full_bar > ok 3 vfio_dma_mapping_mmio_test.vfio_type1v2_iommu.map_full_bar > # RUN > vfio_dma_mapping_mmio_test.vfio_type1v2_iommu.map_partial_bar ... > Mapping BAR4 (partial): vaddr=0x7fad40000000 size=0x1000 iova=0x0 > # OK vfio_dma_mapping_mmio_test.vfio_type1v2_iommu.map_partial_bar > ok 4 vfio_dma_mapping_mmio_test.vfio_type1v2_iommu.map_partial_bar > # PASSED: 4 / 4 tests passed. > # Totals: pass:4 fail:0 xfail:0 xpass:0 skip:0 error:0 > --- > tools/testing/selftests/vfio/Makefile | 1 + > tools/testing/selftests/vfio/lib/vfio_pci_device.c | 28 ++++- > .../selftests/vfio/vfio_dma_mapping_mmio_test.c | 132 > +++++++++++++++++++++ > 3 files changed, 160 insertions(+), 1 deletion(-) > > 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/lib/vfio_pci_device.c > b/tools/testing/selftests/vfio/lib/vfio_pci_device.c > index 13fdb4b0b10f..6f29543856a5 100644 > --- a/tools/testing/selftests/vfio/lib/vfio_pci_device.c > +++ b/tools/testing/selftests/vfio/lib/vfio_pci_device.c > @@ -12,10 +12,13 @@ > #include <sys/mman.h> > > #include <uapi/linux/types.h> > +#include <linux/align.h> > #include <linux/iommufd.h> > +#include <linux/kernel.h> > #include <linux/limits.h> > #include <linux/mman.h> > #include <linux/overflow.h> > +#include <linux/sizes.h> > #include <linux/types.h> > #include <linux/vfio.h> > > @@ -124,20 +127,43 @@ static void vfio_pci_region_get(struct vfio_pci_device > *device, int index, > static void vfio_pci_bar_map(struct vfio_pci_device *device, int index) > { > struct vfio_pci_bar *bar = &device->bars[index]; > + size_t align, size; > + void *map_base, *map_align; > int prot = 0; > > VFIO_ASSERT_LT(index, PCI_STD_NUM_BARS); > VFIO_ASSERT_NULL(bar->vaddr); > VFIO_ASSERT_TRUE(bar->info.flags & VFIO_REGION_INFO_FLAG_MMAP); > + VFIO_ASSERT_GT(bar->info.size, 0); > > if (bar->info.flags & VFIO_REGION_INFO_FLAG_READ) > prot |= PROT_READ; > if (bar->info.flags & VFIO_REGION_INFO_FLAG_WRITE) > prot |= PROT_WRITE; > > - bar->vaddr = mmap(NULL, bar->info.size, prot, MAP_FILE | MAP_SHARED, > + /* > + * Align the mmap for more efficient IOMMU mapping. > + * The largest PUD size supporting huge pfnmap is 1GiB. > + */ > + size = bar->info.size; > + align = min_t(u64, 1ULL << __builtin_ctzll(size), SZ_1G); What's the reason to align to 1ULL << __builtin_ctzll(size) and not just size? > + > + map_base = mmap(NULL, size + align, PROT_NONE, > + MAP_PRIVATE | MAP_ANONYMOUS, -1, 0); > + VFIO_ASSERT_NE(map_base, MAP_FAILED); > + > + map_align = (void *)ALIGN((uintptr_t)map_base, align); > + > + if (map_align > map_base) > + munmap(map_base, map_align - map_base); > + if (align > (size_t)(map_align - map_base)) > + munmap(map_align + size, align - (map_align - map_base)); > + > + bar->vaddr = mmap(map_align, size, prot, MAP_SHARED | MAP_FIXED, > device->fd, bar->info.offset); > VFIO_ASSERT_NE(bar->vaddr, MAP_FAILED); > + > + madvise(bar->vaddr, size, MADV_HUGEPAGE); > } Can you split these changes out into a precursor commit? I think they stand on their own. > > static void vfio_pci_bar_unmap(struct vfio_pci_device *device, int index) > 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..211fa4203b49 > --- /dev/null > +++ b/tools/testing/selftests/vfio/vfio_dma_mapping_mmio_test.c > @@ -0,0 +1,132 @@ > +// 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 int largest_mapped_bar(struct vfio_pci_device *device) > +{ > + int bar_idx = -1; > + 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; > + > + if (!(bar->info.flags & VFIO_REGION_INFO_FLAG_WRITE)) > + continue; nit: Add a comment here. I assume this is because iommu_map() tries to create writable IOMMU mappings? Speaking of, maybe we can add a test that creating writable IOMMU mappings fails for read-only BARs? > + > + if (bar->info.size > bar_size) { > + bar_size = bar->info.size; > + bar_idx = i; > + } > + } > + > + return bar_idx; > +} > + > +FIXTURE(vfio_dma_mapping_mmio_test) { > + struct iommu *iommu; > + struct vfio_pci_device *device; > + struct iova_allocator *iova_allocator; > + int bar_idx; > +}; > + > +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, \ > +} nit: Alignment of trailing backslashes is off. > + > +FIXTURE_VARIANT_ADD_IOMMU_MODE(vfio_type1_iommu); > +FIXTURE_VARIANT_ADD_IOMMU_MODE(vfio_type1v2_iommu); > + > +#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_idx = largest_mapped_bar(self->device); > +} > + > +FIXTURE_TEARDOWN(vfio_dma_mapping_mmio_test) > +{ > + iova_allocator_cleanup(self->iova_allocator); > + vfio_pci_device_cleanup(self->device); > + iommu_cleanup(self->iommu); > +} > + > +TEST_F(vfio_dma_mapping_mmio_test, map_full_bar) > +{ > + struct vfio_pci_bar *bar; > + struct dma_region region; > + > + if (self->bar_idx < 0) > + SKIP(return, "No mappable BAR found on device %s", device_bdf); I think you can do this in the FIXTURE_SETUP() to avoid duplication. > + > + bar = &self->device->bars[self->bar_idx]; > + > + region = (struct dma_region) { > + .vaddr = bar->vaddr, > + .size = bar->info.size, > + .iova = iova_allocator_alloc(self->iova_allocator, > bar->info.size), > + }; > + > + printf("Mapping BAR%d: vaddr=%p size=0x%lx iova=0x%lx\n", > + self->bar_idx, region.vaddr, region.size, region.iova); > + > + iommu_map(self->iommu, ®ion); > + iommu_unmap(self->iommu, ®ion); > +} > + > +TEST_F(vfio_dma_mapping_mmio_test, map_partial_bar) > +{ > + struct vfio_pci_bar *bar; > + struct dma_region region; > + size_t page_size; > + > + if (self->bar_idx < 0) > + SKIP(return, "No mappable BAR found on device %s", device_bdf); > + > + bar = &self->device->bars[self->bar_idx]; > + page_size = getpagesize(); > + > + if (bar->info.size < 2 * page_size) > + SKIP(return, "BAR%d too small for partial mapping test > (size=0x%llx)", > + self->bar_idx, bar->info.size); > + > + region = (struct dma_region) { > + .vaddr = bar->vaddr, > + .size = page_size, > + .iova = iova_allocator_alloc(self->iova_allocator, page_size), > + }; > + > + printf("Mapping BAR%d (partial): vaddr=%p size=0x%lx iova=0x%lx\n", > + self->bar_idx, region.vaddr, region.size, region.iova); > + > + iommu_map(self->iommu, ®ion); > + iommu_unmap(self->iommu, ®ion); > +} > + > +int main(int argc, char *argv[]) > +{ > + device_bdf = vfio_selftests_get_bdf(&argc, argv); > + return test_harness_run(argc, argv); > +} > > --- > base-commit: d721f52e31553a848e0e9947ca15a49c5674aef3 > change-id: 20260107-scratch-amastro-vfio-dma-mapping-mmio-test-eecf25d9a742 > > Best regards, > -- > Alex Mastro <[email protected]> >
