[PATCH v8 12/29] iommufd/viommu: Add driver-defined vDEVICE support

Nicolin Chen
2025-07-05T01:14:25Z

NVIDIA VCMDQ driver will have a driver-defined vDEVICE structure and do
some HW configurations with that.

To allow IOMMU drivers to define their own vDEVICE structures, move the
struct iommufd_vdevice to the public header and provide a pair of viommu
ops, similar to get_viommu_size and viommu_init.

Doing this, however, creates a new window between the vDEVICE allocation
and its driver-level initialization, during which an abort could happen
but it can't invoke a driver destroy function from the struct viommu_ops
since the driver structure isn't initialized yet. vIOMMU object doesn't
have this problem, since its destroy op is set via the viommu_ops by the
driver viommu_init function. Thus, vDEVICE should do something similar:
add a destroy function pointer inside the struct iommufd_vdevice instead
of the struct iommufd_viommu_ops.

Note that there is unlikely a use case for a type dependent vDEVICE, so
a static vdevice_size is probably enough for the near term instead of a
get_vdevice_size function op.

Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Reviewed-by: Pranjal Shrivastava <praan@google.com>
Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>
Signed-off-by: Nicolin Chen <nicolinc@nvidia.com>
---
drivers/iommu/iommufd/iommufd_private.h | 12 ----------
include/linux/iommufd.h | 31 +++++++++++++++++++++++++
drivers/iommu/iommufd/viommu.c | 26 ++++++++++++++++++++-
3 files changed, 56 insertions(+), 13 deletions(-)

diff --git a/drivers/iommu/iommufd/iommufd_private.h b/drivers/iommu/iommufd/iommufd_private.h
index 9fdbf5f21f2e..06b8c2e2d9e6 100644
--- a/drivers/iommu/iommufd/iommufd_private.h
+++ b/drivers/iommu/iommufd/iommufd_private.h
@@ -653,18 +653,6 @@ void iommufd_viommu_destroy(struct iommufd_object *obj);
int iommufd_vdevice_alloc_ioctl(struct iommufd_ucmd *ucmd);
void iommufd_vdevice_destroy(struct iommufd_object *obj);

-struct iommufd_vdevice {
- struct iommufd_object obj;
- struct iommufd_viommu *viommu;
- struct device *dev;
-
- /*
- * Virtual device ID per vIOMMU, e.g. vSID of ARM SMMUv3, vDeviceID of
- * AMD IOMMU, and vRID of Intel VT-d
- */
- u64 virt_id;
-};
-
#ifdef CONFIG_IOMMUFD_TEST
int iommufd_test(struct iommufd_ucmd *ucmd);
void iommufd_selftest_destroy(struct iommufd_object *obj);
diff --git a/include/linux/iommufd.h b/include/linux/iommufd.h
index 2d1bf2f97ee3..bdd10a85eeef 100644
--- a/include/linux/iommufd.h
+++ b/include/linux/iommufd.h
@@ -104,6 +104,21 @@ struct iommufd_viommu {
enum iommu_viommu_type type;
};

+struct iommufd_vdevice {
+ struct iommufd_object obj;
+ struct iommufd_viommu *viommu;
+ struct device *dev;
+
+ /*
+ * Virtual device ID per vIOMMU, e.g. vSID of ARM SMMUv3, vDeviceID of
+ * AMD IOMMU, and vRID of Intel VT-d
+ */
+ u64 virt_id;
+
+ /* Clean up all driver-specific parts of an iommufd_vdevice */
+ void (*destroy)(struct iommufd_vdevice *vdev);
+};
+
/**
* struct iommufd_viommu_ops - vIOMMU specific operations
* @destroy: Clean up all driver-specific parts of an iommufd_viommu. The memory
@@ -120,6 +135,14 @@ struct iommufd_viommu {
* array->entry_num to report the number of handled requests.
* The data structure of the array entry must be defined in
* include/uapi/linux/iommufd.h
+ * @vdevice_size: Size of the driver-defined vDEVICE structure per this vIOMMU
+ * @vdevice_init: Initialize the driver-level structure of a vDEVICE object, or
+ * related HW procedure. @vdev is already initialized by iommufd
+ * core: vdev->dev and vdev->viommu pointers; vdev->id carries a
+ * per-vIOMMU virtual ID (refer to struct iommu_vdevice_alloc in
+ * include/uapi/linux/iommufd.h)
+ * If driver has a deinit function to revert what vdevice_init op
+ * does, it should set it to the @vdev->destroy function pointer
*/
struct iommufd_viommu_ops {
void (*destroy)(struct iommufd_viommu *viommu);
@@ -128,6 +151,8 @@ struct iommufd_viommu_ops {
const struct iommu_user_data *user_data);
int (*cache_invalidate)(struct iommufd_viommu *viommu,
struct iommu_user_data_array *array);
+ const size_t vdevice_size;
+ int (*vdevice_init)(struct iommufd_vdevice *vdev);
};

#if IS_ENABLED(CONFIG_IOMMUFD)
@@ -224,4 +249,10 @@ static inline int iommufd_viommu_report_event(struct iommufd_viommu *viommu,
BUILD_BUG_ON_ZERO(offsetof(drv_struct, member)) + \
BUILD_BUG_ON_ZERO(!__same_type(struct iommufd_viommu, \
((drv_struct *)NULL)->member)))
+
+#define VDEVICE_STRUCT_SIZE(drv_struct, member) \
+ (sizeof(drv_struct) + \
+ BUILD_BUG_ON_ZERO(offsetof(drv_struct, member)) + \
+ BUILD_BUG_ON_ZERO(!__same_type(struct iommufd_vdevice, \
+ ((drv_struct *)NULL)->member)))
#endif
diff --git a/drivers/iommu/iommufd/viommu.c b/drivers/iommu/iommufd/viommu.c
index c0365849f849..081ee6697a11 100644
--- a/drivers/iommu/iommufd/viommu.c
+++ b/drivers/iommu/iommufd/viommu.c
@@ -116,6 +116,8 @@ void iommufd_vdevice_destroy(struct iommufd_object *obj)
container_of(obj, struct iommufd_vdevice, obj);
struct iommufd_viommu *viommu = vdev->viommu;

+ if (vdev->destroy)
+ vdev->destroy(vdev);
/* xa_cmpxchg is okay to fail if alloc failed xa_cmpxchg previously */
xa_cmpxchg(&viommu->vdevs, vdev->virt_id, vdev, NULL, GFP_KERNEL);
refcount_dec(&viommu->obj.users);
@@ -126,6 +128,7 @@ int iommufd_vdevice_alloc_ioctl(struct iommufd_ucmd *ucmd)
{
struct iommu_vdevice_alloc *cmd = ucmd->cmd;
struct iommufd_vdevice *vdev, *curr;
+ size_t vdev_size = sizeof(*vdev);
struct iommufd_viommu *viommu;
struct iommufd_device *idev;
u64 virt_id = cmd->virt_id;
@@ -150,7 +153,22 @@ int iommufd_vdevice_alloc_ioctl(struct iommufd_ucmd *ucmd)
goto out_put_idev;
}

- vdev = iommufd_object_alloc_ucmd(ucmd, vdev, IOMMUFD_OBJ_VDEVICE);
+ if (viommu->ops && viommu->ops->vdevice_size) {
+ /*
+ * It is a driver bug for:
+ * - ops->vdevice_size smaller than the core structure size
+ * - not implementing a pairing ops->vdevice_init op
+ */
+ if (WARN_ON_ONCE(viommu->ops->vdevice_size < vdev_size ||
+ !viommu->ops->vdevice_init)) {
+ rc = -EOPNOTSUPP;
+ goto out_put_idev;
+ }
+ vdev_size = viommu->ops->vdevice_size;
+ }
+
+ vdev = (struct iommufd_vdevice *)_iommufd_object_alloc_ucmd(
+ ucmd, vdev_size, IOMMUFD_OBJ_VDEVICE);
if (IS_ERR(vdev)) {
rc = PTR_ERR(vdev);
goto out_put_idev;
@@ -168,6 +186,12 @@ int iommufd_vdevice_alloc_ioctl(struct iommufd_ucmd *ucmd)
goto out_put_idev;
}

+ if (viommu->ops && viommu->ops->vdevice_init) {
+ rc = viommu->ops->vdevice_init(vdev);
+ if (rc)
+ goto out_put_idev;
+ }
+
cmd->out_vdevice_id = vdev->obj.id;
rc = iommufd_ucmd_respond(ucmd, sizeof(*cmd));

--
2.43.0