vfio: selftests: Introduce vfio_pci_device_test

Introduce a basic VFIO selftest called vfio_pci_device_test to
demonstrate the functionality of the VFIO selftest library and provide
some test coverage of basic VFIO operations, including:

 - Mapping and unmapping DMA
 - Mapping and unmapping BARs
 - Enabling, triggering, and disabling MSI and MSI-x
 - Reading and writing to PCI config space

This test should work with most PCI devices, as long as they are bound
to vfio-pci.

Acked-by: Shuah Khan <skhan@linuxfoundation.org>
Signed-off-by: David Matlack <dmatlack@google.com>
Link: https://lore.kernel.org/r/20250822212518.4156428-4-dmatlack@google.com
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>

tools/testing/selftests/vfio/Makefile

@@ -1,4 +1,5 @@
 CFLAGS = $(KHDR_INCLUDES)
+TEST_GEN_PROGS += vfio_pci_device_test
 include ../lib.mk
 include lib/libvfio.mk
 

tools/testing/selftests/vfio/vfio_pci_device_test.c

@@ -0,0 +1,180 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#include <fcntl.h>
+#include <stdlib.h>
+
+#include <sys/ioctl.h>
+#include <sys/mman.h>
+
+#include <linux/limits.h>
+#include <linux/pci_regs.h>
+#include <linux/sizes.h>
+#include <linux/vfio.h>
+
+#include <vfio_util.h>
+
+#include "../kselftest_harness.h"
+
+static const char *device_bdf;
+
+/*
+ * Limit the number of MSIs enabled/disabled by the test regardless of the
+ * number of MSIs the device itself supports, e.g. to avoid hitting IRTE limits.
+ */
+#define MAX_TEST_MSI 16U
+
+FIXTURE(vfio_pci_device_test) {
+	struct vfio_pci_device *device;
+};
+
+FIXTURE_SETUP(vfio_pci_device_test)
+{
+	self->device = vfio_pci_device_init(device_bdf, VFIO_TYPE1_IOMMU);
+}
+
+FIXTURE_TEARDOWN(vfio_pci_device_test)
+{
+	vfio_pci_device_cleanup(self->device);
+}
+
+TEST_F(vfio_pci_device_test, dma_map_unmap)
+{
+	const u64 size = SZ_2M;
+	void *mem;
+	u64 iova;
+
+	mem = mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_SHARED | MAP_ANONYMOUS, -1, 0);
+	ASSERT_NE(mem, MAP_FAILED);
+
+	iova = (u64)mem;
+
+	vfio_pci_dma_map(self->device, iova, size, mem);
+	printf("Mapped HVA %p (size 0x%lx) at IOVA 0x%lx\n", mem, size, iova);
+	vfio_pci_dma_unmap(self->device, iova, size);
+
+	ASSERT_TRUE(!munmap(mem, SZ_2M));
+}
+
+#define read_pci_id_from_sysfs(_file) ({							\
+	char __sysfs_path[PATH_MAX];								\
+	char __buf[32];										\
+	int __fd;										\
+												\
+	snprintf(__sysfs_path, PATH_MAX, "/sys/bus/pci/devices/%s/%s", device_bdf, _file);	\
+	ASSERT_GT((__fd = open(__sysfs_path, O_RDONLY)), 0);					\
+	ASSERT_GT(read(__fd, __buf, ARRAY_SIZE(__buf)), 0);					\
+	ASSERT_EQ(0, close(__fd));								\
+	(u16)strtoul(__buf, NULL, 0);								\
+})
+
+TEST_F(vfio_pci_device_test, config_space_read_write)
+{
+	u16 vendor, device;
+	u16 command;
+
+	/* Check that Vendor and Device match what the kernel reports. */
+	vendor = read_pci_id_from_sysfs("vendor");
+	device = read_pci_id_from_sysfs("device");
+
+	ASSERT_EQ(vendor, vfio_pci_config_readw(self->device, PCI_VENDOR_ID));
+	ASSERT_EQ(device, vfio_pci_config_readw(self->device, PCI_DEVICE_ID));
+
+	printf("Vendor: %04x, Device: %04x\n", vendor, device);
+
+	command = vfio_pci_config_readw(self->device, PCI_COMMAND);
+	ASSERT_FALSE(command & PCI_COMMAND_MASTER);
+
+	vfio_pci_config_writew(self->device, PCI_COMMAND, command | PCI_COMMAND_MASTER);
+	command = vfio_pci_config_readw(self->device, PCI_COMMAND);
+	ASSERT_TRUE(command & PCI_COMMAND_MASTER);
+	printf("Enabled Bus Mastering (command: %04x)\n", command);
+
+	vfio_pci_config_writew(self->device, PCI_COMMAND, command & ~PCI_COMMAND_MASTER);
+	command = vfio_pci_config_readw(self->device, PCI_COMMAND);
+	ASSERT_FALSE(command & PCI_COMMAND_MASTER);
+	printf("Disabled Bus Mastering (command: %04x)\n", command);
+}
+
+TEST_F(vfio_pci_device_test, validate_bars)
+{
+	struct vfio_pci_bar *bar;
+	int i;
+
+	for (i = 0; i < PCI_STD_NUM_BARS; i++) {
+		bar = &self->device->bars[i];
+
+		if (!(bar->info.flags & VFIO_REGION_INFO_FLAG_MMAP)) {
+			printf("BAR %d does not support mmap()\n", i);
+			ASSERT_EQ(NULL, bar->vaddr);
+			continue;
+		}
+
+		/*
+		 * BARs that support mmap() should be automatically mapped by
+		 * vfio_pci_device_init().
+		 */
+		ASSERT_NE(NULL, bar->vaddr);
+		ASSERT_NE(0, bar->info.size);
+		printf("BAR %d mapped at %p (size 0x%llx)\n", i, bar->vaddr, bar->info.size);
+	}
+}
+
+FIXTURE(vfio_pci_irq_test) {
+	struct vfio_pci_device *device;
+};
+
+FIXTURE_VARIANT(vfio_pci_irq_test) {
+	int irq_index;
+};
+
+FIXTURE_VARIANT_ADD(vfio_pci_irq_test, msi) {
+	.irq_index = VFIO_PCI_MSI_IRQ_INDEX,
+};
+
+FIXTURE_VARIANT_ADD(vfio_pci_irq_test, msix) {
+	.irq_index = VFIO_PCI_MSIX_IRQ_INDEX,
+};
+
+FIXTURE_SETUP(vfio_pci_irq_test)
+{
+	self->device = vfio_pci_device_init(device_bdf, VFIO_TYPE1_IOMMU);
+}
+
+FIXTURE_TEARDOWN(vfio_pci_irq_test)
+{
+	vfio_pci_device_cleanup(self->device);
+}
+
+TEST_F(vfio_pci_irq_test, enable_trigger_disable)
+{
+	bool msix = variant->irq_index == VFIO_PCI_MSIX_IRQ_INDEX;
+	u32 count;
+	u64 value;
+	int i;
+
+	if (msix)
+		count = self->device->msix_info.count;
+	else
+		count = self->device->msi_info.count;
+
+	count = min(count, MAX_TEST_MSI);
+
+	if (!count)
+		SKIP(return, "MSI%s: not supported\n", msix ? "-x" : "");
+
+	vfio_pci_irq_enable(self->device, variant->irq_index, 0, count);
+	printf("MSI%s: enabled %d interrupts\n", msix ? "-x" : "", count);
+
+	for (i = 0; i < count; i++) {
+		vfio_pci_irq_trigger(self->device, variant->irq_index, i);
+		ASSERT_EQ(8, read(self->device->msi_eventfds[i], &value, 8));
+		ASSERT_EQ(1, value);
+	}
+
+	vfio_pci_irq_disable(self->device, variant->irq_index);
+}
+
+int main(int argc, char *argv[])
+{
+	device_bdf = vfio_selftests_get_bdf(&argc, argv);
+	return test_harness_run(argc, argv);
+}