[Qemu-devel] [PATCH] virtio-ccw: fix ring sizing

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

Current code seems to assume ring size is
always decreased but this is not required by spec:
what spec says is just that size can not exceed
the maximum. Fix it up.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
 include/hw/virtio/virtio.h | 1 +
 hw/s390x/virtio-ccw.c      | 2 +-
 hw/virtio/virtio.c         | 5 +++++
 3 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h
index e5541c6..6523bac 100644
--- a/include/hw/virtio/virtio.h
+++ b/include/hw/virtio/virtio.h
@@ -228,6 +228,7 @@ void virtio_queue_set_addr(VirtIODevice *vdev, int n, hwaddr addr);
 hwaddr virtio_queue_get_addr(VirtIODevice *vdev, int n);
 void virtio_queue_set_num(VirtIODevice *vdev, int n, int num);
 int virtio_queue_get_num(VirtIODevice *vdev, int n);
+int virtio_queue_get_max_num(VirtIODevice *vdev, int n);
 int virtio_get_num_queues(VirtIODevice *vdev);
 void virtio_queue_set_rings(VirtIODevice *vdev, int n, hwaddr desc,
                             hwaddr avail, hwaddr used);
diff --git a/hw/s390x/virtio-ccw.c b/hw/s390x/virtio-ccw.c
index 0765068..63c4637 100644
--- a/hw/s390x/virtio-ccw.c
+++ b/hw/s390x/virtio-ccw.c
@@ -149,7 +149,7 @@ static int virtio_ccw_set_vqs(SubchDev *sch, VqInfoBlock *info,
     } else {
         if (info) {
             /* virtio-1 allows changing the ring size. */
-            if (virtio_queue_get_num(vdev, index) < num) {
+            if (virtio_queue_get_max_num(vdev, index) < num) {
                 /* Fail if we exceed the maximum number. */
                 return -EINVAL;
             }
diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index 34065c7..e52fd8e 100644
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -1256,6 +1256,11 @@ int virtio_queue_get_num(VirtIODevice *vdev, int n)
     return vdev->vq[n].vring.num;
 }
 
+int virtio_queue_get_max_num(VirtIODevice *vdev, int n)
+{
+    return vdev->vq[n].vring.num_default;
+}
+
 int virtio_get_num_queues(VirtIODevice *vdev)
 {
     int i;
-- 
MST