[PATCH V4 08/10] vfio:selftest: Handle VFIO noiommu cdev

Jacob Pan
2026-04-14T21:14:20Z

With unsafe DMA noiommu mode, the vfio devices are prefixed with
noiommu-, e.g.
/dev/vfio/
|-- devices
| `-- noiommu-vfio0
|-- noiommu-0
`-- vfio
Let vfio tests, such as luo kexec test, accommodate the noiommu device
files.

Signed-off-by: Jacob Pan <jacob.pan@linux.microsoft.com>
---
.../lib/include/libvfio/vfio_pci_device.h | 1 +
.../selftests/vfio/lib/vfio_pci_device.c | 32 ++++++++++++++++---
.../vfio/vfio_pci_liveupdate_kexec_test.c | 9 ++++++
3 files changed, 38 insertions(+), 4 deletions(-)

diff --git a/tools/testing/selftests/vfio/lib/include/libvfio/vfio_pci_device.h b/tools/testing/selftests/vfio/lib/include/libvfio/vfio_pci_device.h
index 2389c7698335..e2721e36b37e 100644
--- a/tools/testing/selftests/vfio/lib/include/libvfio/vfio_pci_device.h
+++ b/tools/testing/selftests/vfio/lib/include/libvfio/vfio_pci_device.h
@@ -124,6 +124,7 @@ static inline bool vfio_pci_device_match(struct vfio_pci_device *device,
}

const char *vfio_pci_get_cdev_path(const char *bdf);
+int vfio_pci_noiommu_mode_enabled(void);

/* Low-level routines for setting up a struct vfio_pci_device */
struct vfio_pci_device *vfio_pci_device_alloc(const char *bdf, struct iommu *iommu);
diff --git a/tools/testing/selftests/vfio/lib/vfio_pci_device.c b/tools/testing/selftests/vfio/lib/vfio_pci_device.c
index 66ee268110e2..1ba81d169208 100644
--- a/tools/testing/selftests/vfio/lib/vfio_pci_device.c
+++ b/tools/testing/selftests/vfio/lib/vfio_pci_device.c
@@ -225,11 +225,14 @@ void vfio_pci_group_setup(struct vfio_pci_device *device)
struct vfio_group_status group_status = {
.argsz = sizeof(group_status),
};
- char group_path[32];
+ char group_path[64];
int group;

group = vfio_pci_get_group_from_dev(device->bdf);
- snprintf(group_path, sizeof(group_path), "/dev/vfio/%d", group);
+ if (vfio_pci_noiommu_mode_enabled())
+ snprintf(group_path, sizeof(group_path), "/dev/vfio/noiommu-%d", group);
+ else
+ snprintf(group_path, sizeof(group_path), "/dev/vfio/%d", group);

device->group_fd = open(group_path, O_RDWR);
VFIO_ASSERT_GE(device->group_fd, 0, "open(%s) failed\n", group_path);
@@ -294,6 +297,24 @@ static void vfio_pci_device_setup(struct vfio_pci_device *device)
device->msi_eventfds[i] = -1;
}

+
+int vfio_pci_noiommu_mode_enabled(void)
+{
+ const char *path = "/sys/module/vfio/parameters/enable_unsafe_noiommu_mode";
+ FILE *f;
+ int c;
+
+ f = fopen(path, "re");
+ if (!f)
+ return 0;
+
+ c = fgetc(f);
+ fclose(f);
+ if (c == 'Y' || c == 'y')
+ return 1;
+ return 0;
+}
+
const char *vfio_pci_get_cdev_path(const char *bdf)
{
char dir_path[PATH_MAX];
@@ -310,8 +331,11 @@ const char *vfio_pci_get_cdev_path(const char *bdf)
VFIO_ASSERT_NOT_NULL(dir, "Failed to open directory %s\n", dir_path);

while ((entry = readdir(dir)) != NULL) {
- /* Find the file that starts with "vfio" */
- if (strncmp("vfio", entry->d_name, 4))
+ /* Find the file that starts with "noiommu-vfio" or "vfio" */
+ if (vfio_pci_noiommu_mode_enabled()) {
+ if (strncmp("noiommu-vfio", entry->d_name, strlen("noiommu-vfio")))
+ continue;
+ } else if (strncmp("vfio", entry->d_name, 4))
continue;

snprintf(cdev_path, PATH_MAX, "/dev/vfio/devices/%s", entry->d_name);
diff --git a/tools/testing/selftests/vfio/vfio_pci_liveupdate_kexec_test.c b/tools/testing/selftests/vfio/vfio_pci_liveupdate_kexec_test.c
index 36bddfbb88ed..d72f6a58e3e6 100644
--- a/tools/testing/selftests/vfio/vfio_pci_liveupdate_kexec_test.c
+++ b/tools/testing/selftests/vfio/vfio_pci_liveupdate_kexec_test.c
@@ -159,6 +159,15 @@ static void check_open_vfio_device_fails(void)
VFIO_ASSERT_EQ(errno, EBUSY);
free((void *)cdev_path);

+ /*
+ * In no-IOMMU mode the group lives at /dev/vfio/noiommu-<N> and
+ * cannot be added to a Type1 IOMMU container, so the container-based
+ * access check below doesn't apply. The cdev check above already
+ * covers that the device is inaccessible in this mode.
+ */
+ if (vfio_pci_noiommu_mode_enabled())
+ return;
+
for (i = 0; i < nr_iommu_modes; i++) {
if (!iommu_modes[i].container_path)
continue;
--
2.34.1