File 0301-virtio-fix-vq-inuse-recalc-after-mi.patch of Package qemu.8405

From 9d17229c92d6e574322f214579d2e35f7c8bc6b3 Mon Sep 17 00:00:00 2001
From: Halil Pasic <pasic@linux.vnet.ibm.com>
Date: Mon, 19 Dec 2016 16:44:44 +0100
Subject: [PATCH] virtio: fix vq->inuse recalc after migr

Correct recalculation of vq->inuse after migration for the corner case
where the avail_idx has already wrapped but used_idx not yet.

Also change the type of the VirtQueue.inuse to unsigned int. This is
done to be consistent with other members representing sizes (VRing.num),
and because C99 guarantees max ring size < UINT_MAX but does not
guarantee max ring size < INT_MAX.

Signed-off-by: Halil Pasic <pasic@linux.vnet.ibm.com>
Fixes: bccdef6b ("virtio: recalculate vq->inuse after migration")
CC: qemu-stable@nongnu.org
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
(cherry picked from commit e66bcc408146730958d1a840bda85d7ad51e0cd7)
[BR: BSC#1020928]
Signed-off-by: Bruce Rogers <brogers@suse.com>
---
 hw/virtio/virtio.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index 43d7db13e8..ae609746cd 100644
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -85,7 +85,7 @@ struct VirtQueue
 
     uint16_t queue_index;
 
-    int inuse;
+    unsigned int inuse;
 
     uint16_t vector;
     void (*handle_output)(VirtIODevice *vdev, VirtQueue *vq);
@@ -1124,9 +1124,11 @@ int virtio_load(VirtIODevice *vdev, QEMUFile *f, int version_id)
             /*
              * Some devices migrate VirtQueueElements that have been popped
              * from the avail ring but not yet returned to the used ring.
+             * Since max ring size < UINT16_MAX it's safe to use modulo
+             * UINT16_MAX + 1 subtraction.
              */
-            vdev->vq[i].inuse = vdev->vq[i].last_avail_idx -
-                                vdev->vq[i].used_idx;
+            vdev->vq[i].inuse = (uint16_t)(vdev->vq[i].last_avail_idx -
+                                vdev->vq[i].used_idx);
             if (vdev->vq[i].inuse > vdev->vq[i].vring.num) {
                 error_report("VQ %d size 0x%x < last_avail_idx 0x%x - "
                              "used_idx 0x%x",