On 2022/3/19 01:27, Jason Gunthorpe wrote:
+
+/**
+ * iommufd_device_attach - Connect a device to an iommu_domain
+ * @idev: device to attach
+ * @pt_id: Input a IOMMUFD_OBJ_IOAS, or IOMMUFD_OBJ_HW_PAGETABLE
+ * Output the IOMMUFD_OBJ_HW_PAGETABLE ID
+ * @flags: Optional flags
+ *
+ * This connects the device to an iommu_domain, either automatically or manually
+ * selected. Once this completes the device could do DMA.
+ *
+ * The caller should return the resulting pt_id back to userspace.
+ * This function is undone by calling iommufd_device_detach().
+ */
+int iommufd_device_attach(struct iommufd_device *idev, u32 *pt_id,
+ unsigned int flags)
+{
+ struct iommufd_hw_pagetable *hwpt;
+ int rc;
+
+ refcount_inc(&idev->obj.users);
+
+ hwpt = iommufd_hw_pagetable_from_id(idev->ictx, *pt_id, idev->dev);
+ if (IS_ERR(hwpt)) {
+ rc = PTR_ERR(hwpt);
+ goto out_users;
+ }
+
+ mutex_lock(&hwpt->devices_lock);
+ /* FIXME: Use a device-centric iommu api. For now check if the
+ * hw_pagetable already has a device of the same group joined to tell if
+ * we are the first and need to attach the group. */
+ if (!iommufd_hw_pagetable_has_group(hwpt, idev->group)) {
+ phys_addr_t sw_msi_start = 0;
+
+ rc = iommu_attach_group(hwpt->domain, idev->group);
+ if (rc)
+ goto out_unlock;
+
+ /*
+ * hwpt is now the exclusive owner of the group so this is the
+ * first time enforce is called for this group.
+ */
+ rc = iopt_table_enforce_group_resv_regions(
+ &hwpt->ioas->iopt, idev->group, &sw_msi_start);
+ if (rc)
+ goto out_detach;
+ rc = iommufd_device_setup_msi(idev, hwpt, sw_msi_start, flags);
+ if (rc)
+ goto out_iova;
+ }
+
+ idev->hwpt = hwpt;
could the below list_empty check be moved to the above "if branch"? If
above "if branch" is false, that means there is already group attached with
the hwpt->domain. So the hwpt->devices should be non-empty. Only if the
above "if branch" is true, should the hwpt->devices possible to be empty.
So moving it into above "if branch" may be better?
+ if (list_empty(&hwpt->devices)) {
+ rc = iopt_table_add_domain(&hwpt->ioas->iopt, hwpt->domain);
+ if (rc)
+ goto out_iova;
+ }
+ list_add(&idev->devices_item, &hwpt->devices);
+ mutex_unlock(&hwpt->devices_lock);
+
+ *pt_id = idev->hwpt->obj.id;
+ return 0;
+
+out_iova:
+ iopt_remove_reserved_iova(&hwpt->ioas->iopt, idev->group);
+out_detach:
+ iommu_detach_group(hwpt->domain, idev->group);
+out_unlock:
+ mutex_unlock(&hwpt->devices_lock);
+ iommufd_hw_pagetable_put(idev->ictx, hwpt);
+out_users:
+ refcount_dec(&idev->obj.users);
+ return rc;
+}
+EXPORT_SYMBOL_GPL(iommufd_device_attach);
--
Regards,
Yi Liu
