[RFC PATCH 2/3] vfio: selftests: Add iommufd hwpt replace test

[Samiullah Khawaja <skhawaja@google.com>]

Add a test that does iommufd hwpt replace while a DMA is ongoing. This
verifies the hitless replace of IOMMU domain without disrupting the DMA.

Note that the new domain is attached after mapping the required DMA
memory at the same IOVA in the new domain.

Signed-off-by: Samiullah Khawaja <skhawaja@google.com>
---
 tools/testing/selftests/vfio/Makefile         |   1 +
 .../vfio/vfio_iommufd_hwpt_replace_test.c     | 171 ++++++++++++++++++
 2 files changed, 172 insertions(+)
 create mode 100644 tools/testing/selftests/vfio/vfio_iommufd_hwpt_replace_test.c

diff --git a/tools/testing/selftests/vfio/Makefile b/tools/testing/selftests/vfio/Makefile
index 2c32c48db509..01d0e808871b 100644
--- a/tools/testing/selftests/vfio/Makefile
+++ b/tools/testing/selftests/vfio/Makefile
@@ -8,6 +8,7 @@ else
 CFLAGS = $(KHDR_INCLUDES)
 TEST_GEN_PROGS += vfio_dma_mapping_test
 TEST_GEN_PROGS += vfio_dma_mapping_mmio_test
+TEST_GEN_PROGS += vfio_iommufd_hwpt_replace_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_iommufd_hwpt_replace_test.c b/tools/testing/selftests/vfio/vfio_iommufd_hwpt_replace_test.c
new file mode 100644
index 000000000000..3ec243aae626
--- /dev/null
+++ b/tools/testing/selftests/vfio/vfio_iommufd_hwpt_replace_test.c
@@ -0,0 +1,171 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#include <string.h>
+#include <sys/ioctl.h>
+#include <sys/mman.h>
+
+#include <linux/sizes.h>
+#include <linux/vfio.h>
+
+#include <libvfio.h>
+
+#include "kselftest_harness.h"
+
+static const char *device_bdf;
+
+static void region_setup(struct iommu *iommu,
+			 struct iova_allocator *iova_allocator,
+			 struct dma_region *region, u64 size)
+{
+	const int flags = MAP_SHARED | MAP_ANONYMOUS;
+	const int prot = PROT_READ | PROT_WRITE;
+	void *vaddr;
+
+	vaddr = mmap(NULL, size, prot, flags, -1, 0);
+	VFIO_ASSERT_NE(vaddr, MAP_FAILED);
+
+	region->vaddr = vaddr;
+	region->iova = iova_allocator_alloc(iova_allocator, size);
+	region->size = size;
+
+	iommu_map(iommu, region);
+}
+
+static void region_teardown(struct iommu *iommu, struct dma_region *region)
+{
+	iommu_unmap(iommu, region);
+	VFIO_ASSERT_EQ(munmap(region->vaddr, region->size), 0);
+}
+
+FIXTURE(vfio_iommufd_replace_hwpt_test) {
+	struct iommu *iommu;
+	struct vfio_pci_device *device;
+	struct iova_allocator *iova_allocator;
+	struct dma_region memcpy_region;
+
+	u64 size;
+	void *src;
+	void *dst;
+	iova_t src_iova;
+	iova_t dst_iova;
+};
+
+FIXTURE_SETUP(vfio_iommufd_replace_hwpt_test)
+{
+	struct vfio_pci_driver *driver;
+
+	self->iommu = iommu_init("iommufd");
+	self->device = vfio_pci_device_init(device_bdf, self->iommu);
+	self->iova_allocator = iova_allocator_init(self->iommu);
+
+	driver = &self->device->driver;
+
+	region_setup(self->iommu, self->iova_allocator, &self->memcpy_region, SZ_2M);
+	region_setup(self->iommu, self->iova_allocator, &driver->region, SZ_2M);
+
+	if (driver->ops)
+		vfio_pci_driver_init(self->device);
+
+	self->size = self->memcpy_region.size / 2;
+	self->src = self->memcpy_region.vaddr;
+	self->dst = self->src + self->size;
+
+	self->src_iova = to_iova(self->device, self->src);
+	self->dst_iova = to_iova(self->device, self->dst);
+}
+
+FIXTURE_TEARDOWN(vfio_iommufd_replace_hwpt_test)
+{
+	struct vfio_pci_driver *driver = &self->device->driver;
+
+	if (driver->ops)
+		vfio_pci_driver_remove(self->device);
+
+	region_teardown(self->iommu, &self->memcpy_region);
+	region_teardown(self->iommu, &driver->region);
+
+	iova_allocator_cleanup(self->iova_allocator);
+	vfio_pci_device_cleanup(self->device);
+	iommu_cleanup(self->iommu);
+}
+
+FIXTURE_VARIANT(vfio_iommufd_replace_hwpt_test) {
+	u32 attaches;
+};
+
+FIXTURE_VARIANT_ADD(vfio_iommufd_replace_hwpt_test, domain_replace) {
+	.attaches = 1000,
+};
+
+FIXTURE_VARIANT_ADD(vfio_iommufd_replace_hwpt_test, noreplace) {
+	.attaches = 0,
+};
+
+TEST_F_TIMEOUT(vfio_iommufd_replace_hwpt_test, memcpy, 120)
+{
+	struct dma_region memcpy_region = {}, driver_region = {};
+	struct vfio_pci_driver *driver = &self->device->driver;
+	struct iommu *iommu2 = NULL;
+	u64 size = 0;
+	int ret;
+	u32 i;
+
+	if (variant->attaches) {
+		iommu2 = iommufd_iommu_init(self->iommu->iommufd,
+					    self->device->dev_id);
+
+		memcpy_region = self->memcpy_region;
+		driver_region = self->device->driver.region;
+
+		iommu_map(iommu2, &memcpy_region);
+		iommu_map(iommu2, &driver_region);
+	}
+
+	if (driver->ops) {
+		memset(self->src, 'x', self->size);
+		memset(self->dst, 'y', self->size);
+
+		size = min_t(u64, driver->max_memcpy_size, self->size);
+
+		/*
+		 * Fill the device's queue. memcpy_start() returns with
+		 * max_memcpy_count transfers still outstanding.
+		 */
+		vfio_pci_driver_memcpy_start(self->device,
+					     self->src_iova,
+					     self->dst_iova,
+					     size, driver->max_memcpy_count);
+	}
+
+	/*
+	 * Replace the domain repeatedly while that transfer is in flight. Since
+	 * domain replacement is a race with the translation requests, it needs
+	 * to be done multiple times to capture the small window where iommu
+	 * faults can occur.
+	 *
+	 * The loop ends on the original domain, so the teardown below is safe.
+	 */
+	for (i = 0; i < variant->attaches; i++) {
+		vfio_pci_device_attach_iommu(self->device, iommu2);
+		vfio_pci_device_attach_iommu(self->device, self->iommu);
+	}
+
+	if (driver->ops) {
+		ret = vfio_pci_driver_memcpy_wait(self->device);
+
+		ASSERT_EQ(0, ret);
+		ASSERT_EQ(0, memcmp(self->src, self->dst, size));
+	}
+
+	if (iommu2) {
+		iommu_unmap(iommu2, &memcpy_region);
+		iommu_unmap(iommu2, &driver_region);
+		iommu_cleanup(iommu2);
+	}
+}
+
+int main(int argc, char *argv[])
+{
+	device_bdf = vfio_selftests_get_bdf(&argc, argv);
+
+	return test_harness_run(argc, argv);
+}
-- 
2.56.0.rc1.315.gc6ed9934b7-goog