vfio: Export the device set open count

The open count of a device set is the sum of the open counts of all devices in the set. Drivers can use this value to determine whether shared resources are in use without tracking them manually or accessing the private open_count in vfio_device. Signed-off-by: Anthony DeRossi <ajderossi@gmail.com> Reviewed-by: Jason Gunthorpe <jgg@nvidia.com> Reviewed-by: Kevin Tian <kevin.tian@intel.com> Reviewed-by: Yi Liu <yi.l.liu@intel.com> Link: https://lore.kernel.org/r/20221110014027.28780-3-ajderossi@gmail.com Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
mariux64 · Nov 10, 2022 · 5cd189e · 5cd189e
1 parent 7fdba00
commit 5cd189e
Show file tree

Hide file tree

Showing 2 changed files with 14 additions and 0 deletions.
diff --git a/drivers/vfio/vfio_main.c b/drivers/vfio/vfio_main.c
@@ -125,6 +125,19 @@ static void vfio_release_device_set(struct vfio_device *device)
 	xa_unlock(&vfio_device_set_xa);
 }
 
+unsigned int vfio_device_set_open_count(struct vfio_device_set *dev_set)
+{
+	struct vfio_device *cur;
+	unsigned int open_count = 0;
+
+	lockdep_assert_held(&dev_set->lock);
+
+	list_for_each_entry(cur, &dev_set->device_list, dev_set_list)
+		open_count += cur->open_count;
+	return open_count;
+}
+EXPORT_SYMBOL_GPL(vfio_device_set_open_count);
+
 /*
  * Group objects - create, release, get, put, search
  */

diff --git a/include/linux/vfio.h b/include/linux/vfio.h
@@ -189,6 +189,7 @@ int vfio_register_emulated_iommu_dev(struct vfio_device *device);
 void vfio_unregister_group_dev(struct vfio_device *device);
 
 int vfio_assign_device_set(struct vfio_device *device, void *set_id);
+unsigned int vfio_device_set_open_count(struct vfio_device_set *dev_set);
 
 int vfio_mig_get_next_state(struct vfio_device *device,
 			    enum vfio_device_mig_state cur_fsm,