[Qemu-devel] [PATCH] dataplane: sync virtio.c and vring.c virtqueue state

[Qemu-devel] [PATCH] dataplane: sync virtio.c and vring.c virtqueue state

[Stefan Hajnoczi]

Load the virtio.c state into vring.c when we start dataplane mode and
vice versa when stopping dataplane mode.  This patch makes it possible
to start and stop dataplane any time while the guest is running.

This will eventually allow us to go back to QEMU main loop for
bdrv_drain_all() and live migration.  In the meantime, this patch makes
the dataplane lifecycle more robust but should make no visible
difference.  It may be useful in the virtio-net dataplane effort.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 hw/block/dataplane/virtio-blk.c     | 2 +-
 hw/virtio/dataplane/vring.c         | 8 +++++---
 include/hw/virtio/dataplane/vring.h | 2 +-
 3 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/hw/block/dataplane/virtio-blk.c b/hw/block/dataplane/virtio-blk.c
index 0356665..2faed43 100644
--- a/hw/block/dataplane/virtio-blk.c
+++ b/hw/block/dataplane/virtio-blk.c
@@ -537,7 +537,7 @@ void virtio_blk_data_plane_stop(VirtIOBlockDataPlane *s)
     /* Clean up guest notifier (irq) */
     k->set_guest_notifiers(qbus->parent, 1, false);
 
-    vring_teardown(&s->vring);
+    vring_teardown(&s->vring, s->vdev, 0);
     s->started = false;
     s->stopping = false;
 }
diff --git a/hw/virtio/dataplane/vring.c b/hw/virtio/dataplane/vring.c
index e0d6e83..82cc151 100644
--- a/hw/virtio/dataplane/vring.c
+++ b/hw/virtio/dataplane/vring.c
@@ -39,8 +39,8 @@ bool vring_setup(Vring *vring, VirtIODevice *vdev, int n)
 
     vring_init(&vring->vr, virtio_queue_get_num(vdev, n), vring_ptr, 4096);
 
-    vring->last_avail_idx = 0;
-    vring->last_used_idx = 0;
+    vring->last_avail_idx = virtio_queue_get_last_avail_idx(vdev, n);
+    vring->last_used_idx = vring->vr.used->idx;
     vring->signalled_used = 0;
     vring->signalled_used_valid = false;
 
@@ -49,8 +49,10 @@ bool vring_setup(Vring *vring, VirtIODevice *vdev, int n)
     return true;
 }
 
-void vring_teardown(Vring *vring)
+void vring_teardown(Vring *vring, VirtIODevice *vdev, int n)
 {
+    virtio_queue_set_last_avail_idx(vdev, n, vring->last_avail_idx);
+
     hostmem_finalize(&vring->hostmem);
 }
 
diff --git a/include/hw/virtio/dataplane/vring.h b/include/hw/virtio/dataplane/vring.h
index 9380cb5..c0b69ff 100644
--- a/include/hw/virtio/dataplane/vring.h
+++ b/include/hw/virtio/dataplane/vring.h
@@ -50,7 +50,7 @@ static inline void vring_set_broken(Vring *vring)
 }
 
 bool vring_setup(Vring *vring, VirtIODevice *vdev, int n);
-void vring_teardown(Vring *vring);
+void vring_teardown(Vring *vring, VirtIODevice *vdev, int n);
 void vring_disable_notification(VirtIODevice *vdev, Vring *vring);
 bool vring_enable_notification(VirtIODevice *vdev, Vring *vring);
 bool vring_should_notify(VirtIODevice *vdev, Vring *vring);
-- 
1.8.1.4

Re: [Qemu-devel] [PATCH] dataplane: sync virtio.c and vring.c virtqueue state

[Stefan Hajnoczi]

On Mon, Jul 01, 2013 at 01:29:17PM +0200, Stefan Hajnoczi wrote:
> Load the virtio.c state into vring.c when we start dataplane mode and
> vice versa when stopping dataplane mode.  This patch makes it possible
> to start and stop dataplane any time while the guest is running.
> 
> This will eventually allow us to go back to QEMU main loop for
> bdrv_drain_all() and live migration.  In the meantime, this patch makes
> the dataplane lifecycle more robust but should make no visible
> difference.  It may be useful in the virtio-net dataplane effort.
> 
> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
> ---
>  hw/block/dataplane/virtio-blk.c     | 2 +-
>  hw/virtio/dataplane/vring.c         | 8 +++++---
>  include/hw/virtio/dataplane/vring.h | 2 +-
>  3 files changed, 7 insertions(+), 5 deletions(-)

Applied to my block tree:
https://github.com/stefanha/qemu/commits/block

Stefan