[PATCH v6 20/27] vfio: selftests: Add iommufd noiommu mode
From: Vipin Sharma
Date: Mon Nov 02 2026 - 15:44:58 EST
Add an opt-in iommufd_noiommu mode (MODE_IOMMUFD_NOIOMMU) for devices
bound to vfio-pci in noiommu mode. When a device is in noiommu mode, its
VFIO character device is named /dev/vfio/devices/noiommu-vfioX (opening
it requires CAP_SYS_RAWIO), and binding and attaching to an iommufd IOAS
use a software page table.
Add __vfio_pci_get_cdev_path(bdf, noiommu) to look up either the regular
or the noiommu cdev path and return NULL when none is present, and make
vfio_pci_cdev_open() select the cdev based on mode->noiommu.
Because a device in noiommu mode DMAs directly to physical addresses,
tests that program arbitrary or unmapped IOVAs would corrupt memory.
Keep MODE_IOMMUFD_NOIOMMU out of FIXTURE_VARIANT_ADD_ALL_IOMMU_MODES()
so that only noiommu-aware tests opt into it.
Signed-off-by: Vipin Sharma <vipinsh@xxxxxxxxxx>
---
.../vfio/lib/include/libvfio/iommu.h | 17 ++++++++++
.../lib/include/libvfio/vfio_pci_device.h | 7 +++++
tools/testing/selftests/vfio/lib/iommu.c | 9 +++++-
.../selftests/vfio/lib/vfio_pci_device.c | 31 +++++++++++++------
4 files changed, 53 insertions(+), 11 deletions(-)
diff --git a/tools/testing/selftests/vfio/lib/include/libvfio/iommu.h b/tools/testing/selftests/vfio/lib/include/libvfio/iommu.h
index e9a3386a4719..e652b8caf5bb 100644
--- a/tools/testing/selftests/vfio/lib/include/libvfio/iommu.h
+++ b/tools/testing/selftests/vfio/lib/include/libvfio/iommu.h
@@ -13,6 +13,12 @@ struct iommu_mode {
const char *name;
const char *container_path;
unsigned long iommu_type;
+ /*
+ * For devices bound to vfio-pci in noiommu mode, i.e. not behind an
+ * IOMMU. Such devices DMA to the addresses programmed into them as
+ * physical addresses.
+ */
+ bool noiommu;
};
extern const char *default_iommu_mode;
@@ -67,6 +73,17 @@ struct iommu_iova_range *iommu_iova_ranges(struct iommu *iommu, u32 *nranges);
#define MODE_IOMMUFD_COMPAT_TYPE1V2 "iommufd_compat_type1v2"
#define MODE_IOMMUFD "iommufd"
+/*
+ * iommufd with a device bound to vfio-pci in noiommu mode
+ * (vfio.enable_unsafe_noiommu_mode=1 and CONFIG_IOMMUFD_NOIOMMU), whose cdev
+ * is /dev/vfio/devices/noiommu-vfioX. Opening it requires CAP_SYS_RAWIO.
+ *
+ * Not part of FIXTURE_VARIANT_ADD_ALL_IOMMU_MODES(): tests must opt in, since
+ * the device DMAs to IOVAs as physical addresses, and tests that DMA to
+ * arbitrary or unmapped IOVAs would corrupt memory.
+ */
+#define MODE_IOMMUFD_NOIOMMU "iommufd_noiommu"
+
/*
* Generator for VFIO selftests fixture variants that replicate across all
* possible IOMMU modes. Tests must define FIXTURE_VARIANT_ADD_IOMMU_MODE()
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 9a62bfb6b440..bfadeb362723 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
@@ -154,6 +154,13 @@ static inline bool vfio_pci_device_match(struct vfio_pci_device *device,
(device_id == vfio_pci_config_readw(device, PCI_DEVICE_ID));
}
+/*
+ * Return the path of the VFIO cdev of @bdf, or NULL if there is none. The cdev
+ * of a device bound to vfio-pci in noiommu mode is named noiommu-vfioX rather
+ * than vfioX, and @noiommu selects which of the two to look for. Free with
+ * free().
+ */
+const char *__vfio_pci_get_cdev_path(const char *bdf, bool noiommu);
const char *vfio_pci_get_cdev_path(const char *bdf);
void vfio_pci_group_setup(struct vfio_pci_device *device, const char *bdf);
diff --git a/tools/testing/selftests/vfio/lib/iommu.c b/tools/testing/selftests/vfio/lib/iommu.c
index b6f3c5c84e01..0df49646d016 100644
--- a/tools/testing/selftests/vfio/lib/iommu.c
+++ b/tools/testing/selftests/vfio/lib/iommu.c
@@ -22,7 +22,10 @@
const char *default_iommu_mode = MODE_IOMMUFD;
-/* Reminder: Keep in sync with FIXTURE_VARIANT_ADD_ALL_IOMMU_MODES(). */
+/*
+ * Reminder: Keep in sync with FIXTURE_VARIANT_ADD_ALL_IOMMU_MODES(), which
+ * deliberately leaves out the noiommu modes.
+ */
static const struct iommu_mode iommu_modes[] = {
{
.name = MODE_VFIO_TYPE1_IOMMU,
@@ -47,6 +50,10 @@ static const struct iommu_mode iommu_modes[] = {
{
.name = MODE_IOMMUFD,
},
+ {
+ .name = MODE_IOMMUFD_NOIOMMU,
+ .noiommu = true,
+ },
};
static const struct iommu_mode *lookup_iommu_mode(const char *iommu_mode)
diff --git a/tools/testing/selftests/vfio/lib/vfio_pci_device.c b/tools/testing/selftests/vfio/lib/vfio_pci_device.c
index af789c859586..b0deef2b0e3f 100644
--- a/tools/testing/selftests/vfio/lib/vfio_pci_device.c
+++ b/tools/testing/selftests/vfio/lib/vfio_pci_device.c
@@ -380,35 +380,42 @@ static void vfio_pci_device_setup(struct vfio_pci_device *device)
device->msi_eventfds[i] = -1;
}
-const char *vfio_pci_get_cdev_path(const char *bdf)
+const char *__vfio_pci_get_cdev_path(const char *bdf, bool noiommu)
{
+ const char *prefix = noiommu ? "noiommu-vfio" : "vfio";
char dir_path[PATH_MAX];
struct dirent *entry;
- char *cdev_path;
+ char *cdev_path = NULL;
DIR *dir;
- cdev_path = calloc_assert(PATH_MAX, 1);
-
snprintf_assert(dir_path, sizeof(dir_path), "/sys/bus/pci/devices/%s/vfio-dev/", bdf);
dir = opendir(dir_path);
- VFIO_ASSERT_NOT_NULL(dir, "Failed to open directory %s\n", dir_path);
+ if (!dir)
+ return NULL;
while ((entry = readdir(dir)) != NULL) {
- /* Find the file that starts with "vfio" */
- if (strncmp("vfio", entry->d_name, 4))
+ if (strncmp(prefix, entry->d_name, strlen(prefix)))
continue;
+ cdev_path = calloc_assert(PATH_MAX, 1);
snprintf_assert(cdev_path, PATH_MAX, "/dev/vfio/devices/%s", entry->d_name);
break;
}
- VFIO_ASSERT_NE(cdev_path[0], 0, "Failed to find vfio cdev file.\n");
VFIO_ASSERT_EQ(closedir(dir), 0);
return cdev_path;
}
+const char *vfio_pci_get_cdev_path(const char *bdf)
+{
+ const char *cdev_path = __vfio_pci_get_cdev_path(bdf, false);
+
+ VFIO_ASSERT_NOT_NULL(cdev_path, "Failed to find vfio cdev file for %s\n", bdf);
+ return cdev_path;
+}
+
int __vfio_device_bind_iommufd(int device_fd, int iommufd, const char *vf_token)
{
struct vfio_device_bind_iommufd args = {
@@ -449,10 +456,14 @@ static void vfio_device_attach_iommufd_pt(int device_fd, u32 pt_id)
void vfio_pci_cdev_open(struct vfio_pci_device *device, const char *bdf)
{
- const char *cdev_path = vfio_pci_get_cdev_path(bdf);
+ bool noiommu = device->iommu->mode->noiommu;
+ const char *cdev_path = __vfio_pci_get_cdev_path(bdf, noiommu);
+
+ VFIO_ASSERT_NOT_NULL(cdev_path, "Failed to find %svfio cdev file for %s\n",
+ noiommu ? "noiommu-" : "", bdf);
device->fd = open(cdev_path, O_RDWR);
- VFIO_ASSERT_GE(device->fd, 0);
+ VFIO_ASSERT_GE(device->fd, 0, "open(%s) failed\n", cdev_path);
free((void *)cdev_path);
}
--
2.56.0.317.g454f8302e1-goog