[PATCH] virtio-pci: mask notifier error handling fixups

["Michael S. Tsirkin" <mst@redhat.com>]

Fix virtio-pci error handling in the mask notifiers: be careful to undo
exactly what we did so far.

Reported-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---

This is for qemu-kvm only.

 hw/virtio-pci.c |   12 ++++++++++++
 1 files changed, 12 insertions(+), 0 deletions(-)

diff --git a/hw/virtio-pci.c b/hw/virtio-pci.c
index bf3cf4f..dd8887a 100644
--- a/hw/virtio-pci.c
+++ b/hw/virtio-pci.c
@@ -612,6 +612,9 @@ static int virtio_pci_mask_notifier(PCIDevice *dev, unsigned vector,
     return 0;
 undo:
     while (--n >= 0) {
+        if (virtio_queue_vector(vdev, n) != vector) {
+            continue;
+        }
         virtio_pci_mask_vq(dev, vector, virtio_get_queue(vdev, n), !masked);
     }
     return r;
@@ -681,9 +684,18 @@ static int virtio_pci_set_guest_notifiers(void *opaque, bool assign)
 
 assign_error:
     /* We get here on assignment failure. Recover by undoing for VQs 0 .. n. */
+    if (assign) {
+        msix_unset_mask_notifier(&proxy->pci_dev);
+    }
+
     while (--n >= 0) {
         virtio_pci_set_guest_notifier(opaque, n, !assign);
     }
+
+    if (!assign) {
+        msix_set_mask_notifier(&proxy->pci_dev,
+                               virtio_pci_mask_notifier);
+    }
     return r;
 }
 
-- 
1.7.3.2.91.g446ac