[PATCH 1/4] vfio: selftests: Introduce vfio_dma_mapping_perf_test

[Aaron Lewis <aaronlewis@google.com>]

Introduce a tool to aid in latency testing rather than a traditional
pass/fail test. The goal is to make the test configurable to expose
latency issues and make them easy to reproduce and share.

Start with a basic test that performs a simple DMA map/unmap and reports
the duration of each operation. Report the following four metrics:

  1. Time taken by mmap().
  2. Time taken to map a DMA region.
  3. Time taken to unmap a DMA region.
  4. Time taken by munmap().

Subsequent commits in this series will introduce more features to allow
for a wider variety of testing.

Signed-off-by: Aaron Lewis <aaronlewis@google.com>
---
 tools/testing/selftests/vfio/Makefile         |   1 +
 .../vfio/vfio_dma_mapping_perf_test.c         | 124 ++++++++++++++++++
 2 files changed, 125 insertions(+)
 create mode 100644 tools/testing/selftests/vfio/vfio_dma_mapping_perf_test.c

diff --git a/tools/testing/selftests/vfio/Makefile b/tools/testing/selftests/vfio/Makefile
index e6e8cb52ab03..9f620c5ef6ab 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_dma_mapping_perf_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_perf_test.c b/tools/testing/selftests/vfio/vfio_dma_mapping_perf_test.c
new file mode 100644
index 000000000000..87d84450fc47
--- /dev/null
+++ b/tools/testing/selftests/vfio/vfio_dma_mapping_perf_test.c
@@ -0,0 +1,124 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#include <limits.h>
+#include <stdio.h>
+#include <sys/mman.h>
+#include <time.h>
+#include <unistd.h>
+
+#include <linux/iommufd.h>
+#include <linux/limits.h>
+#include <linux/memfd.h>
+#include <linux/mman.h>
+#include <linux/sizes.h>
+#include <linux/time64.h>
+#include <linux/vfio.h>
+
+#include <libvfio.h>
+
+#include "kselftest_harness.h"
+
+static const char *device_bdf;
+
+struct iommu_mapping {
+	u64 pgd;
+	u64 p4d;
+	u64 pud;
+	u64 pmd;
+	u64 pte;
+};
+
+static void timer_start(struct timespec *start) {
+	clock_gettime(CLOCK_MONOTONIC, start);
+}
+
+static double timer_elapsed_ms(struct timespec start)
+{
+	struct timespec end;
+
+	clock_gettime(CLOCK_MONOTONIC, &end);
+
+	return (double)(end.tv_sec - start.tv_sec) * MSEC_PER_SEC +
+	       (double)(end.tv_nsec - start.tv_nsec) / NSEC_PER_MSEC;
+}
+
+FIXTURE(vfio_dma_mapping_perf_test) {
+	struct iommu *iommu;
+	struct vfio_pci_device *device;
+	struct iova_allocator *iova_allocator;
+};
+
+FIXTURE_VARIANT(vfio_dma_mapping_perf_test) {
+	const char *iommu_mode;
+	int mmap_flags;
+};
+
+#define FIXTURE_VARIANT_ADD_IOMMU_MODE(_iommu_mode, _name, _mmap_flags)	       \
+FIXTURE_VARIANT_ADD(vfio_dma_mapping_perf_test, _iommu_mode ## _ ## _name) {   \
+	.iommu_mode = #_iommu_mode,					       \
+	.mmap_flags = MAP_ANONYMOUS | MAP_PRIVATE | (_mmap_flags),	       \
+}
+
+FIXTURE_VARIANT_ADD_ALL_IOMMU_MODES(anonymous, 0);
+FIXTURE_VARIANT_ADD_ALL_IOMMU_MODES(anonymous_hugetlb_2mb, MAP_HUGETLB | MAP_HUGE_2MB);
+FIXTURE_VARIANT_ADD_ALL_IOMMU_MODES(anonymous_hugetlb_1gb, MAP_HUGETLB | MAP_HUGE_1GB);
+
+#undef FIXTURE_VARIANT_ADD_IOMMU_MODE
+
+FIXTURE_SETUP(vfio_dma_mapping_perf_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);
+}
+
+FIXTURE_TEARDOWN(vfio_dma_mapping_perf_test)
+{
+	iova_allocator_cleanup(self->iova_allocator);
+	vfio_pci_device_cleanup(self->device);
+	iommu_cleanup(self->iommu);
+}
+
+TEST_F(vfio_dma_mapping_perf_test, dma_map_unmap)
+{
+	const u64 size = SZ_1G;
+	const int flags = variant->mmap_flags;
+	struct dma_region region;
+	struct timespec start;
+	u64 unmapped;
+	int rc;
+
+	timer_start(&start);
+	region.vaddr = mmap(NULL, size, PROT_READ | PROT_WRITE, flags, -1, 0);
+	printf("Completed mmap() in %.2lfms\n", timer_elapsed_ms(start));
+
+	/* Skip the test if there aren't enough HugeTLB pages available. */
+	if (flags & MAP_HUGETLB && region.vaddr == MAP_FAILED)
+		SKIP(return, "mmap() failed: %s (%d)\n", strerror(errno), errno);
+	else
+		ASSERT_NE(region.vaddr, MAP_FAILED);
+
+	region.iova = iova_allocator_alloc(self->iova_allocator, size);
+	region.size = size;
+
+	timer_start(&start);
+	iommu_map(self->iommu, &region);
+	printf("Mapped HVA %p (size %luG) at IOVA 0x%lx in %.2lfms\n",
+	       region.vaddr, size / SZ_1G, region.iova, timer_elapsed_ms(start));
+	ASSERT_EQ(region.iova, to_iova(self->device, region.vaddr));
+
+	timer_start(&start);
+	rc = __iommu_unmap(self->iommu, &region, &unmapped);
+	printf("Unmapped IOVA 0x%lx in %.2lfms\n", region.iova, timer_elapsed_ms(start));
+	ASSERT_EQ(rc, 0);
+	ASSERT_EQ(unmapped, region.size);
+
+	timer_start(&start);
+	ASSERT_TRUE(!munmap(region.vaddr, size));
+	printf("Completed munmap() in %.2lfms\n", timer_elapsed_ms(start));
+}
+
+int main(int argc, char *argv[])
+{
+	device_bdf = vfio_selftests_get_bdf(&argc, argv);
+	return test_harness_run(argc, argv);
+}
-- 
2.55.0.rc0.799.gd6f94ed593-goog