vfio: Move device_del() before waiting for the last vfio_device registration refcount

device_del() destroys the vfio-dev/vfioX under the sysfs for vfio_device.
There is no reason to keep it while the device is going to be unregistered.

This movement is also a preparation for adding vfio_device cdev. Kernel
should remove the cdev node of the vfio_device to avoid new registration
refcount increment while the device is going to be unregistered.

Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Tested-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
Tested-by: Yanting Jiang <yanting.jiang@intel.com>
Signed-off-by: Yi Liu <yi.l.liu@intel.com>
Link: https://lore.kernel.org/r/20230718135551.6592-18-yi.l.liu@intel.com
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>

diff --git a/drivers/vfio/vfio_main.c b/drivers/vfio/vfio_main.c
index 6d45caa..294bb5e 100644 (file)
--- a/drivers/vfio/vfio_main.c
+++ b/drivers/vfio/vfio_main.c
@@ -338,6 +338,9 @@ void vfio_unregister_group_dev(struct vfio_device *device)
         */
        vfio_device_group_unregister(device);
 
+       /* Balances device_add in register path */
+       device_del(&device->device);
+
        vfio_device_put_registration(device);
        rc = try_wait_for_completion(&device->comp);
        while (rc <= 0) {
@@ -361,9 +364,6 @@ void vfio_unregister_group_dev(struct vfio_device *device)
                }
        }
 
-       /* Balances device_add in register path */
-       device_del(&device->device);
-
        /* Balances vfio_device_set_group in register path */
        vfio_device_remove_group(device);
 }