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virtio: Report real progress in VQ aio poll handler

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In virtio_queue_host_notifier_aio_poll, not all "!virtio_queue_empty()"
cases are making true progress.

Currently the offending one is virtio-scsi event queue, whose handler
does nothing if no event is pending. As a result aio_poll() will spin on
the "non-empty" VQ and take 100% host CPU.

Fix this by reporting actual progress from virtio queue aio handlers.

Reported-by: Ed Swierk <eswierk@skyportsystems.com>
Signed-off-by: Fam Zheng <famz@redhat.com>
Tested-by: Ed Swierk <eswierk@skyportsystems.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
This commit is contained in:
Fam Zheng 2017-02-09 16:40:47 +08:00 • committed by Michael S. Tsirkin
parent 4bb571d857
commit 0793169870
8 changed files with 45 additions and 26 deletions
Download patch file Download diff file Expand all files Collapse all files

4
hw/block/dataplane/virtio-blk.c
View file

@ -147,7 +147,7 @@ void virtio_blk_data_plane_destroy(VirtIOBlockDataPlane *s)
g_free(s);
}
static void virtio_blk_data_plane_handle_output(VirtIODevice *vdev,
static bool virtio_blk_data_plane_handle_output(VirtIODevice *vdev,
VirtQueue *vq)
{
VirtIOBlock *s = (VirtIOBlock *)vdev;
@ -155,7 +155,7 @@ static void virtio_blk_data_plane_handle_output(VirtIODevice *vdev,
assert(s->dataplane);
assert(s->dataplane_started);
virtio_blk_handle_vq(s, vq);
return virtio_blk_handle_vq(s, vq);
}
/* Context: QEMU global mutex held */

12
hw/block/virtio-blk.c
View file

@ -581,10 +581,11 @@ static int virtio_blk_handle_request(VirtIOBlockReq *req, MultiReqBuffer *mrb)
return 0;
}
void virtio_blk_handle_vq(VirtIOBlock *s, VirtQueue *vq)
bool virtio_blk_handle_vq(VirtIOBlock *s, VirtQueue *vq)
{
VirtIOBlockReq *req;
MultiReqBuffer mrb = {};
bool progress = false;
blk_io_plug(s->blk);
@ -592,6 +593,7 @@ void virtio_blk_handle_vq(VirtIOBlock *s, VirtQueue *vq)
virtio_queue_set_notification(vq, 0);
while ((req = virtio_blk_get_request(s, vq))) {
progress = true;
if (virtio_blk_handle_request(req, &mrb)) {
virtqueue_detach_element(req->vq, &req->elem, 0);
virtio_blk_free_request(req);
@ -607,6 +609,12 @@ void virtio_blk_handle_vq(VirtIOBlock *s, VirtQueue *vq)
}
blk_io_unplug(s->blk);
return progress;
}
static void virtio_blk_handle_output_do(VirtIOBlock *s, VirtQueue *vq)
{
virtio_blk_handle_vq(s, vq);
}
static void virtio_blk_handle_output(VirtIODevice *vdev, VirtQueue *vq)
@ -622,7 +630,7 @@ static void virtio_blk_handle_output(VirtIODevice *vdev, VirtQueue *vq)
return;
}
}
virtio_blk_handle_vq(s, vq);
virtio_blk_handle_output_do(s, vq);
}
static void virtio_blk_dma_restart_bh(void *opaque)