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[Qemu-devel] [PATCH 2/2] virtio-blk: use aio handler for data plane
From: |
Michael S. Tsirkin |
Subject: |
[Qemu-devel] [PATCH 2/2] virtio-blk: use aio handler for data plane |
Date: |
Tue, 29 Mar 2016 16:42:14 +0300 |
In addition to handling IO in vcpu thread and
in io thread, blk dataplane introduces yet another mode:
handling it by aio.
This reuses the same handler as previous modes,
which triggers races as these were not designed to be reentrant.
As a temporary fix, use a separate handler just for aio, and
disable regular handlers when dataplane is active.
Signed-off-by: Michael S. Tsirkin <address@hidden>
---
include/hw/virtio/virtio-blk.h | 2 ++
hw/block/dataplane/virtio-blk.c | 13 +++++++++++++
hw/block/virtio-blk.c | 28 ++++++++++++++++++----------
3 files changed, 33 insertions(+), 10 deletions(-)
diff --git a/include/hw/virtio/virtio-blk.h b/include/hw/virtio/virtio-blk.h
index ae84d92..df517ff 100644
--- a/include/hw/virtio/virtio-blk.h
+++ b/include/hw/virtio/virtio-blk.h
@@ -85,4 +85,6 @@ void virtio_blk_handle_request(VirtIOBlockReq *req,
MultiReqBuffer *mrb);
void virtio_blk_submit_multireq(BlockBackend *blk, MultiReqBuffer *mrb);
+void virtio_blk_handle_vq(VirtIOBlock *s, VirtQueue *vq);
+
#endif
diff --git a/hw/block/dataplane/virtio-blk.c b/hw/block/dataplane/virtio-blk.c
index 36f3d2b..7d1f3b2 100644
--- a/hw/block/dataplane/virtio-blk.c
+++ b/hw/block/dataplane/virtio-blk.c
@@ -184,6 +184,17 @@ void virtio_blk_data_plane_destroy(VirtIOBlockDataPlane *s)
g_free(s);
}
+static void virtio_blk_data_plane_handle_output(VirtIODevice *vdev,
+ VirtQueue *vq)
+{
+ VirtIOBlock *s = VIRTIO_BLK(vdev);
+
+ assert(s->dataplane);
+ assert(s->dataplane_started);
+
+ virtio_blk_handle_vq(s, vq);
+}
+
/* Context: QEMU global mutex held */
void virtio_blk_data_plane_start(VirtIOBlockDataPlane *s)
{
@@ -226,6 +237,7 @@ void virtio_blk_data_plane_start(VirtIOBlockDataPlane *s)
/* Get this show started by hooking up our callbacks */
aio_context_acquire(s->ctx);
+ virtio_set_queue_aio(s->vq, virtio_blk_data_plane_handle_output);
virtio_queue_aio_set_host_notifier_handler(s->vq, s->ctx, true, true);
aio_context_release(s->ctx);
return;
@@ -262,6 +274,7 @@ void virtio_blk_data_plane_stop(VirtIOBlockDataPlane *s)
/* Stop notifications for new requests from guest */
virtio_queue_aio_set_host_notifier_handler(s->vq, s->ctx, false, false);
+ virtio_set_queue_aio(s->vq, NULL);
/* Drain and switch bs back to the QEMU main loop */
blk_set_aio_context(s->conf->conf.blk, qemu_get_aio_context());
diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c
index cb710f1..5717f09 100644
--- a/hw/block/virtio-blk.c
+++ b/hw/block/virtio-blk.c
@@ -577,20 +577,11 @@ void virtio_blk_handle_request(VirtIOBlockReq *req,
MultiReqBuffer *mrb)
}
}
-static void virtio_blk_handle_output(VirtIODevice *vdev, VirtQueue *vq)
+void virtio_blk_handle_vq(VirtIOBlock *s, VirtQueue *vq)
{
- VirtIOBlock *s = VIRTIO_BLK(vdev);
VirtIOBlockReq *req;
MultiReqBuffer mrb = {};
- /* Some guests kick before setting VIRTIO_CONFIG_S_DRIVER_OK so start
- * dataplane here instead of waiting for .set_status().
- */
- if (s->dataplane && !s->dataplane_started) {
- virtio_blk_data_plane_start(s->dataplane);
- return;
- }
-
blk_io_plug(s->blk);
while ((req = virtio_blk_get_request(s))) {
@@ -604,6 +595,23 @@ static void virtio_blk_handle_output(VirtIODevice *vdev,
VirtQueue *vq)
blk_io_unplug(s->blk);
}
+static void virtio_blk_handle_output(VirtIODevice *vdev, VirtQueue *vq)
+{
+ VirtIOBlock *s = VIRTIO_BLK(vdev);
+
+ if (s->dataplane) {
+ /* Some guests kick before setting VIRTIO_CONFIG_S_DRIVER_OK so start
+ * dataplane here instead of waiting for .set_status().
+ */
+ if (!s->dataplane_started) {
+ virtio_blk_data_plane_start(s->dataplane);
+ }
+ return;
+ }
+
+ virtio_blk_handle_vq(s, vq);
+}
+
static void virtio_blk_dma_restart_bh(void *opaque)
{
VirtIOBlock *s = opaque;
--
MST
Re: [Qemu-devel] [PATCH 0/2] dataplane: fix start/stop races, Michael S. Tsirkin, 2016/03/29
Re: [Qemu-devel] [PATCH 0/2] dataplane: fix start/stop races, Cornelia Huck, 2016/03/29
Re: [Qemu-devel] [PATCH 0/2] dataplane: fix start/stop races, Christian Borntraeger, 2016/03/29