iommufd/viommu: Add driver-defined vDEVICE support

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.

Link: https://patch.msgid.link/r/1e751c01da7863c669314d8e27fdb89eabcf5605.1752126748.git.nicolinc@nvidia.com
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>
Reviewed-by: Vasant Hegde <vasant.hegde@amd.com>
Signed-off-by: Nicolin Chen <nicolinc@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

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);

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));
 

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