On 02/14/2016 06:17 PM, Paolo Bonzini wrote:
> In disabled mode, virtio-blk dataplane seems to be enabled, but flow
> actually goes through the normal virtio path. This patch simplifies a bit
> the handling of disabled mode. In disabled mode, virtio_blk_handle_output
> might be called even if s->dataplane is not NULL.
>
> This is a bit tricky, because the current check for s->dataplane will
> always trigger, causing a continuous stream of calls to
> virtio_blk_data_plane_start. Unfortunately, these calls will not
> do anything. To fix this, set the "started" flag even in disabled
> mode, and skip virtio_blk_data_plane_start if the started flag is true.
> The resulting changes also prepare the code for the next patch, were
> virtio-blk dataplane will reuse the same virtio_blk_handle_output function
> as "regular" virtio-blk.
>
> Because struct VirtIOBlockDataPlane is opaque in virtio-blk.c, we have
> to move s->dataplane->started inside struct VirtIOBlock.
>
> Signed-off-by: Paolo Bonzini <pbonz...@redhat.com>
I have some random crashes at startup
Stack trace of thread 48326:
#0 0x000002aa2e0cce46 bdrv_co_do_rw (qemu-system-s390x)
#1 0x000002aa2e159e8e coroutine_trampoline (qemu-system-s390x)
#2 0x000003ffbc35150a __makecontext_ret (libc.so.6)
that I was able to bisect.
commit 2906cddfecff21af20eedab43288b485a679f9ac does crash regularly,
2906cddfecff21af20eedab43288b485a679f9ac^ does not.
I will try to find somebody that looks into that - unless you have an idea.
Christian
> ---
> hw/block/dataplane/virtio-blk.c | 21 +++++++++------------
> hw/block/virtio-blk.c | 2 +-
> include/hw/virtio/virtio-blk.h | 1 +
> 3 files changed, 11 insertions(+), 13 deletions(-)
>
> diff --git a/hw/block/dataplane/virtio-blk.c b/hw/block/dataplane/virtio-blk.c
> index 03b81bc..cc521c1 100644
> --- a/hw/block/dataplane/virtio-blk.c
> +++ b/hw/block/dataplane/virtio-blk.c
> @@ -28,7 +28,6 @@
> #include "qom/object_interfaces.h"
>
> struct VirtIOBlockDataPlane {
> - bool started;
> bool starting;
> bool stopping;
> bool disabled;
> @@ -264,11 +263,7 @@ void virtio_blk_data_plane_start(VirtIOBlockDataPlane *s)
> VirtQueue *vq;
> int r;
>
> - if (s->started || s->disabled) {
> - return;
> - }
> -
> - if (s->starting) {
> + if (vblk->dataplane_started || s->starting) {
> return;
> }
>
> @@ -300,7 +295,7 @@ void virtio_blk_data_plane_start(VirtIOBlockDataPlane *s)
> vblk->complete_request = complete_request_vring;
>
> s->starting = false;
> - s->started = true;
> + vblk->dataplane_started = true;
> trace_virtio_blk_data_plane_start(s);
>
> blk_set_aio_context(s->conf->conf.blk, s->ctx);
> @@ -319,9 +314,10 @@ void virtio_blk_data_plane_start(VirtIOBlockDataPlane *s)
> k->set_guest_notifiers(qbus->parent, 1, false);
> fail_guest_notifiers:
> vring_teardown(&s->vring, s->vdev, 0);
> - s->disabled = true;
> fail_vring:
> + s->disabled = true;
> s->starting = false;
> + vblk->dataplane_started = true;
> }
>
> /* Context: QEMU global mutex held */
> @@ -331,13 +327,14 @@ void virtio_blk_data_plane_stop(VirtIOBlockDataPlane *s)
> VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
> VirtIOBlock *vblk = VIRTIO_BLK(s->vdev);
>
> + if (!vblk->dataplane_started || s->stopping) {
> + return;
> + }
>
> /* Better luck next time. */
> if (s->disabled) {
> s->disabled = false;
> - return;
> - }
> - if (!s->started || s->stopping) {
> + vblk->dataplane_started = false;
> return;
> }
> s->stopping = true;
> @@ -364,6 +361,6 @@ void virtio_blk_data_plane_stop(VirtIOBlockDataPlane *s)
> /* Clean up guest notifier (irq) */
> k->set_guest_notifiers(qbus->parent, 1, false);
>
> - s->started = false;
> + vblk->dataplane_started = false;
> s->stopping = false;
> }
> diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c
> index c427698..e04c8f5 100644
> --- a/hw/block/virtio-blk.c
> +++ b/hw/block/virtio-blk.c
> @@ -589,7 +589,7 @@ static void virtio_blk_handle_output(VirtIODevice *vdev,
> VirtQueue *vq)
> /* Some guests kick before setting VIRTIO_CONFIG_S_DRIVER_OK so start
> * dataplane here instead of waiting for .set_status().
> */
> - if (s->dataplane) {
> + if (s->dataplane && !s->dataplane_started) {
> virtio_blk_data_plane_start(s->dataplane);
> return;
> }
> diff --git a/include/hw/virtio/virtio-blk.h b/include/hw/virtio/virtio-blk.h
> index 199bb0e..781969d 100644
> --- a/include/hw/virtio/virtio-blk.h
> +++ b/include/hw/virtio/virtio-blk.h
> @@ -56,6 +56,7 @@ typedef struct VirtIOBlock {
> /* Function to push to vq and notify guest */
> void (*complete_request)(struct VirtIOBlockReq *req, unsigned char
> status);
> Notifier migration_state_notifier;
> + bool dataplane_started;
> struct VirtIOBlockDataPlane *dataplane;
> } VirtIOBlock;
>
