debian/patches/extra/0006-virtio-recalculate-vq-inuse-after-migration.patch

   1 From ed3112487835fb5c5ec685e15032641c25018f87 Mon Sep 17 00:00:00 2001
   2 From: Stefan Hajnoczi <stefanha@redhat.com>
   3 Date: Mon, 15 Aug 2016 13:54:15 +0100
   4 Subject: [PATCH 06/10] virtio: recalculate vq->inuse after migration
   5
   6 The vq->inuse field is not migrated.  Many devices don't hold
   7 VirtQueueElements across migration so it doesn't matter that vq->inuse
   8 starts at 0 on the destination QEMU.
   9
  10 At least virtio-serial, virtio-blk, and virtio-balloon migrate while
  11 holding VirtQueueElements.  For these devices we need to recalculate
  12 vq->inuse upon load so the value is correct.
  13
  14 Cc: qemu-stable@nongnu.org
  15 Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
  16 Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
  17 Reviewed-by: Cornelia Huck <cornelia.huck@de.ibm.com>
  18 Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
  19 Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
  20 ---
  21  hw/virtio/virtio.c | 15 +++++++++++++++
  22  1 file changed, 15 insertions(+)
  23
  24 diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
  25 index 111ad8e..486147b 100644
  26 --- a/hw/virtio/virtio.c
  27 +++ b/hw/virtio/virtio.c
  28 @@ -1629,6 +1629,21 @@ int virtio_load(VirtIODevice *vdev, QEMUFile *f, int version_id)
  29              }
  30              vdev->vq[i].used_idx = vring_used_idx(&vdev->vq[i]);
  31              vdev->vq[i].shadow_avail_idx = vring_avail_idx(&vdev->vq[i]);
  32 +
  33 +            /*
  34 +             * Some devices migrate VirtQueueElements that have been popped
  35 +             * from the avail ring but not yet returned to the used ring.
  36 +             */
  37 +            vdev->vq[i].inuse = vdev->vq[i].last_avail_idx -
  38 +                                vdev->vq[i].used_idx;
  39 +            if (vdev->vq[i].inuse > vdev->vq[i].vring.num) {
  40 +                error_report("VQ %d size 0x%x < last_avail_idx 0x%x - "
  41 +                             "used_idx 0x%x",
  42 +                             i, vdev->vq[i].vring.num,
  43 +                             vdev->vq[i].last_avail_idx,
  44 +                             vdev->vq[i].used_idx);
  45 +                return -1;
  46 +            }
  47          }
  48      }
  49
  50 --
  51 2.1.4
  52