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Message-ID: <aPfbU4rYkSUDG4D0@devgpu012.nha5.facebook.com>
Date: Tue, 21 Oct 2025 12:13:23 -0700
From: Alex Mastro <amastro@...com>
To: David Matlack <dmatlack@...gle.com>
CC: Alex Williamson <alex@...zbot.org>,
Alejandro Jimenez
<alejandro.j.jimenez@...cle.com>,
Jason Gunthorpe <jgg@...pe.ca>, <kvm@...r.kernel.org>,
<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 0/3] vfio: handle DMA map/unmap up to the addressable
limit
On Tue, Oct 21, 2025 at 09:31:59AM -0700, David Matlack wrote:
> On Tue, Oct 21, 2025 at 9:26 AM Alex Mastro <amastro@...com> wrote:
> > On Mon, Oct 20, 2025 at 03:36:33PM -0600, Alex Williamson wrote:
> > > Should we also therefore expand the DMA mapping tests in
> > > tools/testing/selftests/vfio to include an end of address space test?
> >
> > Yes. I will append such a commit to the end of the series in v5. Our VFIO tests
> > are built on top of a hermetic rust wrapper library over VFIO ioctls, but they
> > aren't quite ready to be open sourced yet.
>
> Feel free to reach out if you have any questions about writing or
> running the VFIO selftests.
Thanks David. I built and ran using below. I am not too familiar with
kselftests, so open to tips.
$ make LLVM=1 -j kselftest-install INSTALL_PATH=/tmp/kst TARGETS="vfio"
$ VFIO_SELFTESTS_BDF=0000:05:00.0 /tmp/kst/run_kselftest.sh
I added the following. Is this the right direction? Is multiple fixtures per
file OK? Seems related enough to vfio_dma_mapping_test.c to keep together.
I updated the *_unmap function signatures to return the count of bytes unmapped,
since that is part of the test pass criteria. Also added unmap_all flavors,
since those exercise different code paths than range-based unmap.
Relevant test output:
# # RUN vfio_dma_map_limit_test.vfio_type1_iommu.end_of_address_space ...
# Mapped HVA 0x7f6638222000 (size 0x1000) at IOVA 0xfffffffffffff000
# Mapped HVA 0x7f6638222000 (size 0x1000) at IOVA 0xfffffffffffff000
# # OK vfio_dma_map_limit_test.vfio_type1_iommu.end_of_address_space
# ok 16 vfio_dma_map_limit_test.vfio_type1_iommu.end_of_address_space
# # RUN vfio_dma_map_limit_test.vfio_type1v2_iommu.end_of_address_space ...
# Mapped HVA 0x7f6638222000 (size 0x1000) at IOVA 0xfffffffffffff000
# Mapped HVA 0x7f6638222000 (size 0x1000) at IOVA 0xfffffffffffff000
# # OK vfio_dma_map_limit_test.vfio_type1v2_iommu.end_of_address_space
# ok 17 vfio_dma_map_limit_test.vfio_type1v2_iommu.end_of_address_space
# # RUN vfio_dma_map_limit_test.iommufd_compat_type1.end_of_address_space ...
# Mapped HVA 0x7f6638222000 (size 0x1000) at IOVA 0xfffffffffffff000
# Mapped HVA 0x7f6638222000 (size 0x1000) at IOVA 0xfffffffffffff000
# # OK vfio_dma_map_limit_test.iommufd_compat_type1.end_of_address_space
# ok 18 vfio_dma_map_limit_test.iommufd_compat_type1.end_of_address_space
# # RUN vfio_dma_map_limit_test.iommufd_compat_type1v2.end_of_address_space ...
# Mapped HVA 0x7f6638222000 (size 0x1000) at IOVA 0xfffffffffffff000
# Mapped HVA 0x7f6638222000 (size 0x1000) at IOVA 0xfffffffffffff000
# # OK vfio_dma_map_limit_test.iommufd_compat_type1v2.end_of_address_space
# ok 19 vfio_dma_map_limit_test.iommufd_compat_type1v2.end_of_address_space
# # RUN vfio_dma_map_limit_test.iommufd.end_of_address_space ...
# Mapped HVA 0x7f6638222000 (size 0x1000) at IOVA 0xfffffffffffff000
# Mapped HVA 0x7f6638222000 (size 0x1000) at IOVA 0xfffffffffffff000
diff --git a/tools/testing/selftests/vfio/lib/include/vfio_util.h b/tools/testing/selftests/vfio/lib/include/vfio_util.h
index ed31606e01b7..8e9d40845ccc 100644
--- a/tools/testing/selftests/vfio/lib/include/vfio_util.h
+++ b/tools/testing/selftests/vfio/lib/include/vfio_util.h
@@ -208,8 +208,9 @@ void vfio_pci_device_reset(struct vfio_pci_device *device);
void vfio_pci_dma_map(struct vfio_pci_device *device,
struct vfio_dma_region *region);
-void vfio_pci_dma_unmap(struct vfio_pci_device *device,
- struct vfio_dma_region *region);
+u64 vfio_pci_dma_unmap(struct vfio_pci_device *device,
+ struct vfio_dma_region *region);
+u64 vfio_pci_dma_unmap_all(struct vfio_pci_device *device);
void vfio_pci_config_access(struct vfio_pci_device *device, bool write,
size_t config, size_t size, void *data);
diff --git a/tools/testing/selftests/vfio/lib/vfio_pci_device.c b/tools/testing/selftests/vfio/lib/vfio_pci_device.c
index 0921b2451ba5..f5ae68a7df9c 100644
--- a/tools/testing/selftests/vfio/lib/vfio_pci_device.c
+++ b/tools/testing/selftests/vfio/lib/vfio_pci_device.c
@@ -183,7 +183,7 @@ void vfio_pci_dma_map(struct vfio_pci_device *device,
list_add(®ion->link, &device->dma_regions);
}
-static void vfio_iommu_dma_unmap(struct vfio_pci_device *device,
+static u64 vfio_iommu_dma_unmap(struct vfio_pci_device *device,
struct vfio_dma_region *region)
{
struct vfio_iommu_type1_dma_unmap args = {
@@ -193,9 +193,25 @@ static void vfio_iommu_dma_unmap(struct vfio_pci_device *device,
};
ioctl_assert(device->container_fd, VFIO_IOMMU_UNMAP_DMA, &args);
+
+ return args.size;
+}
+
+static u64 vfio_iommu_dma_unmap_all(struct vfio_pci_device *device)
+{
+ struct vfio_iommu_type1_dma_unmap args = {
+ .argsz = sizeof(args),
+ .iova = 0,
+ .size = 0,
+ .flags = VFIO_DMA_UNMAP_FLAG_ALL,
+ };
+
+ ioctl_assert(device->container_fd, VFIO_IOMMU_UNMAP_DMA, &args);
+
+ return args.size;
}
-static void iommufd_dma_unmap(struct vfio_pci_device *device,
+static u64 iommufd_dma_unmap(struct vfio_pci_device *device,
struct vfio_dma_region *region)
{
struct iommu_ioas_unmap args = {
@@ -206,17 +222,54 @@ static void iommufd_dma_unmap(struct vfio_pci_device *device,
};
ioctl_assert(device->iommufd, IOMMU_IOAS_UNMAP, &args);
+
+ return args.length;
+}
+
+static u64 iommufd_dma_unmap_all(struct vfio_pci_device *device)
+{
+ struct iommu_ioas_unmap args = {
+ .size = sizeof(args),
+ .iova = 0,
+ .length = UINT64_MAX,
+ .ioas_id = device->ioas_id,
+ };
+
+ ioctl_assert(device->iommufd, IOMMU_IOAS_UNMAP, &args);
+
+ return args.length;
}
-void vfio_pci_dma_unmap(struct vfio_pci_device *device,
+u64 vfio_pci_dma_unmap(struct vfio_pci_device *device,
struct vfio_dma_region *region)
{
+ u64 unmapped;
+
if (device->iommufd)
- iommufd_dma_unmap(device, region);
+ unmapped = iommufd_dma_unmap(device, region);
else
- vfio_iommu_dma_unmap(device, region);
+ unmapped = vfio_iommu_dma_unmap(device, region);
list_del(®ion->link);
+
+ return unmapped;
+}
+
+u64 vfio_pci_dma_unmap_all(struct vfio_pci_device *device)
+{
+ u64 unmapped;
+ struct vfio_dma_region *curr, *next;
+
+ if (device->iommufd)
+ unmapped = iommufd_dma_unmap_all(device);
+ else
+ unmapped = vfio_iommu_dma_unmap_all(device);
+
+ list_for_each_entry_safe(curr, next, &device->dma_regions, link) {
+ list_del(&curr->link);
+ }
+
+ return unmapped;
}
static void vfio_pci_region_get(struct vfio_pci_device *device, int index,
diff --git a/tools/testing/selftests/vfio/vfio_dma_mapping_test.c b/tools/testing/selftests/vfio/vfio_dma_mapping_test.c
index ab19c54a774d..e908c1fe7103 100644
--- a/tools/testing/selftests/vfio/vfio_dma_mapping_test.c
+++ b/tools/testing/selftests/vfio/vfio_dma_mapping_test.c
@@ -122,6 +122,8 @@ FIXTURE_TEARDOWN(vfio_dma_mapping_test)
vfio_pci_device_cleanup(self->device);
}
+#undef FIXTURE_VARIANT_ADD_IOMMU_MODE
+
TEST_F(vfio_dma_mapping_test, dma_map_unmap)
{
const u64 size = variant->size ?: getpagesize();
@@ -192,6 +194,61 @@ TEST_F(vfio_dma_mapping_test, dma_map_unmap)
ASSERT_TRUE(!munmap(region.vaddr, size));
}
+FIXTURE(vfio_dma_map_limit_test) {
+ struct vfio_pci_device *device;
+};
+
+FIXTURE_VARIANT(vfio_dma_map_limit_test) {
+ const char *iommu_mode;
+};
+
+#define FIXTURE_VARIANT_ADD_IOMMU_MODE(_iommu_mode) \
+FIXTURE_VARIANT_ADD(vfio_dma_map_limit_test, _iommu_mode) { \
+ .iommu_mode = #_iommu_mode, \
+}
+
+FIXTURE_VARIANT_ADD_ALL_IOMMU_MODES();
+
+FIXTURE_SETUP(vfio_dma_map_limit_test)
+{
+ self->device = vfio_pci_device_init(device_bdf, variant->iommu_mode);
+}
+
+FIXTURE_TEARDOWN(vfio_dma_map_limit_test)
+{
+ vfio_pci_device_cleanup(self->device);
+}
+
+#undef FIXTURE_VARIANT_ADD_IOMMU_MODE
+
+TEST_F(vfio_dma_map_limit_test, end_of_address_space)
+{
+ struct vfio_dma_region region = {};
+ u64 size = getpagesize();
+ u64 unmapped;
+
+ region.vaddr = mmap(NULL, size, PROT_READ | PROT_WRITE,
+ MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
+ ASSERT_NE(region.vaddr, MAP_FAILED);
+
+ region.iova = ~(iova_t)0 & ~(size - 1);
+ region.size = size;
+
+ vfio_pci_dma_map(self->device, ®ion);
+ printf("Mapped HVA %p (size 0x%lx) at IOVA 0x%lx\n", region.vaddr, size, region.iova);
+ ASSERT_EQ(region.iova, to_iova(self->device, region.vaddr));
+
+ unmapped = vfio_pci_dma_unmap(self->device, ®ion);
+ ASSERT_EQ(unmapped, size);
+
+ vfio_pci_dma_map(self->device, ®ion);
+ printf("Mapped HVA %p (size 0x%lx) at IOVA 0x%lx\n", region.vaddr, size, region.iova);
+ ASSERT_EQ(region.iova, to_iova(self->device, region.vaddr));
+
+ unmapped = vfio_pci_dma_unmap_all(self->device);
+ ASSERT_EQ(unmapped, size);
+}
+
int main(int argc, char *argv[])
{
device_bdf = vfio_selftests_get_bdf(&argc, argv);
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