[Qemu-devel] [PATCH for-1.6] virtio: clear signalled_used_valid when switching from dataplane

[Stefan Hajnoczi <stefanha@redhat.com>]

When the dataplane thread stops, its vring.c implementation synchronizes
vring state back to virtio.c so we can continue emulating the virtio
device.

This patch ensures that virtio.c's signalled_used_valid flag is reset so
that we do not suppress guest notifications due to stale signalled_used
values.

Suggested-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 hw/virtio/dataplane/vring.c | 1 +
 hw/virtio/virtio.c          | 5 +++++
 include/hw/virtio/virtio.h  | 1 +
 3 files changed, 7 insertions(+)

diff --git a/hw/virtio/dataplane/vring.c b/hw/virtio/dataplane/vring.c
index 82cc151..351a343 100644
--- a/hw/virtio/dataplane/vring.c
+++ b/hw/virtio/dataplane/vring.c
@@ -52,6 +52,7 @@ bool vring_setup(Vring *vring, VirtIODevice *vdev, int n)
 void vring_teardown(Vring *vring, VirtIODevice *vdev, int n)
 {
     virtio_queue_set_last_avail_idx(vdev, n, vring->last_avail_idx);
+    virtio_queue_invalidate_signalled_used(vdev, n);
 
     hostmem_finalize(&vring->hostmem);
 }
diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index 09f62c6..706bdf4 100644
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -1059,6 +1059,11 @@ void virtio_queue_set_last_avail_idx(VirtIODevice *vdev, int n, uint16_t idx)
     vdev->vq[n].last_avail_idx = idx;
 }
 
+void virtio_queue_invalidate_signalled_used(VirtIODevice *vdev, int n)
+{
+    vdev->vq[n].signalled_used_valid = false;
+}
+
 VirtQueue *virtio_get_queue(VirtIODevice *vdev, int n)
 {
     return vdev->vq + n;
diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h
index d7e9e0f..a90522d 100644
--- a/include/hw/virtio/virtio.h
+++ b/include/hw/virtio/virtio.h
@@ -237,6 +237,7 @@ hwaddr virtio_queue_get_used_size(VirtIODevice *vdev, int n);
 hwaddr virtio_queue_get_ring_size(VirtIODevice *vdev, int n);
 uint16_t virtio_queue_get_last_avail_idx(VirtIODevice *vdev, int n);
 void virtio_queue_set_last_avail_idx(VirtIODevice *vdev, int n, uint16_t idx);
+void virtio_queue_invalidate_signalled_used(VirtIODevice *vdev, int n);
 VirtQueue *virtio_get_queue(VirtIODevice *vdev, int n);
 uint16_t virtio_get_queue_index(VirtQueue *vq);
 int virtio_queue_get_id(VirtQueue *vq);
-- 
1.8.3.1