[Qemu-devel] [RFC 2/2] vfio: listener unregister before unset container

[Peter Xu <peterx@redhat.com>]

After previous patch, listener unregister will need the container to be
alive.  Let's move this unregister phase to be before unset container,
since that operation will free the backend container in kernel, then
we'll get these after previous patch:

qemu-system-x86_64: VFIO_UNMAP_DMA: -22
qemu-system-x86_64: vfio_dma_unmap(0x559bf53a4590, 0x0, 0xa0000) = -22 (Invalid argument)

Signed-off-by: Peter Xu <peterx@redhat.com>
---
 hw/vfio/common.c | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/hw/vfio/common.c b/hw/vfio/common.c
index b77be3a8b3..76cf28d462 100644
--- a/hw/vfio/common.c
+++ b/hw/vfio/common.c
@@ -1161,19 +1161,27 @@ static void vfio_disconnect_container(VFIOGroup *group)
 {
     VFIOContainer *container = group->container;
 
+    QLIST_REMOVE(group, container_next);
+    group->container = NULL;
+
+    /*
+     * Explicitly release the listener first before unset container,
+     * since unset may destroy the backend container if it's the last
+     * group.
+     */
+    if (QLIST_EMPTY(&container->group_list)) {
+        vfio_listener_release(container);
+    }
+
     if (ioctl(group->fd, VFIO_GROUP_UNSET_CONTAINER, &container->fd)) {
         error_report("vfio: error disconnecting group %d from container",
                      group->groupid);
     }
 
-    QLIST_REMOVE(group, container_next);
-    group->container = NULL;
-
     if (QLIST_EMPTY(&container->group_list)) {
         VFIOAddressSpace *space = container->space;
         VFIOGuestIOMMU *giommu, *tmp;
 
-        vfio_listener_release(container);
         QLIST_REMOVE(container, next);
 
         QLIST_FOREACH_SAFE(giommu, &container->giommu_list, giommu_next, tmp) {
-- 
2.14.3