iommufd/viommu: Add iommufd_viommu_find_dev helper

This avoids a bigger trouble of exposing struct iommufd_device and struct
iommufd_vdevice in the public header.

Link: https://patch.msgid.link/r/84fa7c624db4d4508067ccfdf42059533950180a.1730836308.git.nicolinc@nvidia.com
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Nicolin Chen <nicolinc@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

Author: nicolinc

drivers/iommu/iommufd/driver.c

@@ -36,5 +36,18 @@ struct iommufd_object *_iommufd_object_alloc(struct iommufd_ctx *ictx,
 }
 EXPORT_SYMBOL_NS_GPL(_iommufd_object_alloc, IOMMUFD);
 
+/* Caller should xa_lock(&viommu->vdevs) to protect the return value */
+struct device *iommufd_viommu_find_dev(struct iommufd_viommu *viommu,
+				       unsigned long vdev_id)
+{
+	struct iommufd_vdevice *vdev;
+
+	lockdep_assert_held(&viommu->vdevs.xa_lock);
+
+	vdev = xa_load(&viommu->vdevs, vdev_id);
+	return vdev ? vdev->dev : NULL;
+}
+EXPORT_SYMBOL_NS_GPL(iommufd_viommu_find_dev, IOMMUFD);
+
 MODULE_DESCRIPTION("iommufd code shared with builtin modules");
 MODULE_LICENSE("GPL");

include/linux/iommufd.h

@@ -185,13 +185,21 @@ static inline int iommufd_vfio_compat_set_no_iommu(struct iommufd_ctx *ictx)
 struct iommufd_object *_iommufd_object_alloc(struct iommufd_ctx *ictx,
 					     size_t size,
 					     enum iommufd_object_type type);
+struct device *iommufd_viommu_find_dev(struct iommufd_viommu *viommu,
+				       unsigned long vdev_id);
 #else /* !CONFIG_IOMMUFD_DRIVER_CORE */
 static inline struct iommufd_object *
 _iommufd_object_alloc(struct iommufd_ctx *ictx, size_t size,
 		      enum iommufd_object_type type)
 {
 	return ERR_PTR(-EOPNOTSUPP);
 }
+
+static inline struct device *
+iommufd_viommu_find_dev(struct iommufd_viommu *viommu, unsigned long vdev_id)
+{
+	return NULL;
+}
 #endif /* CONFIG_IOMMUFD_DRIVER_CORE */
 
 /*