iommufd: Use the iommufd_group to avoid duplicate MSI setup

This only needs to be done once per group, not once per device. The once
per device was a way to make the device list work. Since we are abandoning
this we can optimize things a bit.

Link: https://lore.kernel.org/r/[email protected]
Reviewed-by: Kevin Tian <[email protected]>
Tested-by: Nicolin Chen <[email protected]>
Signed-off-by: Jason Gunthorpe <[email protected]>

Author: jgunthorpe

drivers/iommu/iommufd/device.c

@@ -361,10 +361,6 @@ int iommufd_hw_pagetable_attach(struct iommufd_hw_pagetable *hwpt,
 	if (rc)
 		goto err_unlock;
 
-	rc = iommufd_device_setup_msi(idev, hwpt, sw_msi_start);
-	if (rc)
-		goto err_unresv;
-
 	/*
 	 * Only attach to the group once for the first device that is in the
 	 * group. All the other devices will follow this attachment. The user
@@ -373,6 +369,10 @@ int iommufd_hw_pagetable_attach(struct iommufd_hw_pagetable *hwpt,
 	 * attachment.
 	 */
 	if (list_empty(&idev->igroup->device_list)) {
+		rc = iommufd_device_setup_msi(idev, hwpt, sw_msi_start);
+		if (rc)
+			goto err_unresv;
+
 		rc = iommu_attach_group(hwpt->domain, idev->igroup->group);
 		if (rc)
 			goto err_unresv;