virtio save/load is currently sending last_avail_idx, but inuse isn't.
This causes inconsistent state when using Kemari which replays
outstanding requests on the secondary. By letting last_avail_idx to
be updated after inuse is decreased, it would be possible to replay
the outstanding requests. Noth that live migration shouldn't be
affected because it waits until flushing all requests. Also in
conjunction with event-tap, requests inversion should be avoided.
Signed-off-by: Yoshiaki Tamura <tamura.yoshiaki@xxxxxxxxxxxxx>
---
hw/virtio.c | 8 +++++++-
1 files changed, 7 insertions(+), 1 deletions(-)
diff --git a/hw/virtio.c b/hw/virtio.c
index 07dbf86..f915c46 100644
--- a/hw/virtio.c
+++ b/hw/virtio.c
@@ -72,7 +72,7 @@ struct VirtQueue
VRing vring;
target_phys_addr_t pa;
uint16_t last_avail_idx;
- int inuse;
+ uint16_t inuse;
uint16_t vector;
void (*handle_output)(VirtIODevice *vdev, VirtQueue *vq);
VirtIODevice *vdev;
@@ -671,6 +671,7 @@ void virtio_save(VirtIODevice *vdev, QEMUFile *f)
qemu_put_be32(f, vdev->vq[i].vring.num);
qemu_put_be64(f, vdev->vq[i].pa);
qemu_put_be16s(f, &vdev->vq[i].last_avail_idx);
+ qemu_put_be16s(f, &vdev->vq[i].inuse);
if (vdev->binding->save_queue)
vdev->binding->save_queue(vdev->binding_opaque, i, f);
}
@@ -710,6 +711,11 @@ int virtio_load(VirtIODevice *vdev, QEMUFile *f)
vdev->vq[i].vring.num = qemu_get_be32(f);
vdev->vq[i].pa = qemu_get_be64(f);
qemu_get_be16s(f, &vdev->vq[i].last_avail_idx);
+ qemu_get_be16s(f, &vdev->vq[i].inuse);
+
+ /* revert last_avail_idx if there are outstanding emulation. */
+ vdev->vq[i].last_avail_idx -= vdev->vq[i].inuse;
+ vdev->vq[i].inuse = 0;
if (vdev->vq[i].pa) {
uint16_t nheads;
--
1.7.1.2
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