From bd58ab40c3fcfdd94f5524626ae13c43818bd23a Mon Sep 17 00:00:00 2001 From: Stefan Hajnoczi Date: Tue, 16 May 2023 15:02:34 -0400 Subject: [PATCH] virtio: make it possible to detach host notifier from any thread virtio_queue_aio_detach_host_notifier() does two things: 1. It removes the fd handler from the event loop. 2. It processes the virtqueue one last time. The first step can be peformed by any thread and without taking the AioContext lock. The second step may need the AioContext lock (depending on the device implementation) and runs in the thread where request processing takes place. virtio-blk and virtio-scsi therefore call virtio_queue_aio_detach_host_notifier() from a BH that is scheduled in AioContext. The next patch will introduce a .drained_begin() function that needs to call virtio_queue_aio_detach_host_notifier(). .drained_begin() functions cannot call aio_poll() to wait synchronously for the BH. It is possible for a .drained_poll() callback to asynchronously wait for the BH, but that is more complex than necessary here. Move the virtqueue processing out to the callers of virtio_queue_aio_detach_host_notifier() so that the function can be called from any thread. This is in preparation for the next patch. Signed-off-by: Stefan Hajnoczi Message-Id: <20230516190238.8401-17-stefanha@redhat.com> Signed-off-by: Kevin Wolf --- hw/block/dataplane/virtio-blk.c | 7 +++++++ hw/scsi/virtio-scsi-dataplane.c | 14 ++++++++++++++ hw/virtio/virtio.c | 3 --- 3 files changed, 21 insertions(+), 3 deletions(-) diff --git a/hw/block/dataplane/virtio-blk.c b/hw/block/dataplane/virtio-blk.c index af1c24c40c..4f5c7cd55f 100644 --- a/hw/block/dataplane/virtio-blk.c +++ b/hw/block/dataplane/virtio-blk.c @@ -287,8 +287,15 @@ static void virtio_blk_data_plane_stop_bh(void *opaque) for (i = 0; i < s->conf->num_queues; i++) { VirtQueue *vq = virtio_get_queue(s->vdev, i); + EventNotifier *host_notifier = virtio_queue_get_host_notifier(vq); virtio_queue_aio_detach_host_notifier(vq, s->ctx); + + /* + * Test and clear notifier after disabling event, in case poll callback + * didn't have time to run. + */ + virtio_queue_host_notifier_read(host_notifier); } } diff --git a/hw/scsi/virtio-scsi-dataplane.c b/hw/scsi/virtio-scsi-dataplane.c index f3214e1c57..b3a1ed21f7 100644 --- a/hw/scsi/virtio-scsi-dataplane.c +++ b/hw/scsi/virtio-scsi-dataplane.c @@ -71,12 +71,26 @@ static void virtio_scsi_dataplane_stop_bh(void *opaque) { VirtIOSCSI *s = opaque; VirtIOSCSICommon *vs = VIRTIO_SCSI_COMMON(s); + EventNotifier *host_notifier; int i; virtio_queue_aio_detach_host_notifier(vs->ctrl_vq, s->ctx); + host_notifier = virtio_queue_get_host_notifier(vs->ctrl_vq); + + /* + * Test and clear notifier after disabling event, in case poll callback + * didn't have time to run. + */ + virtio_queue_host_notifier_read(host_notifier); + virtio_queue_aio_detach_host_notifier(vs->event_vq, s->ctx); + host_notifier = virtio_queue_get_host_notifier(vs->event_vq); + virtio_queue_host_notifier_read(host_notifier); + for (i = 0; i < vs->conf.num_queues; i++) { virtio_queue_aio_detach_host_notifier(vs->cmd_vqs[i], s->ctx); + host_notifier = virtio_queue_get_host_notifier(vs->cmd_vqs[i]); + virtio_queue_host_notifier_read(host_notifier); } } diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c index 272d930721..cb09cb6464 100644 --- a/hw/virtio/virtio.c +++ b/hw/virtio/virtio.c @@ -3516,9 +3516,6 @@ void virtio_queue_aio_attach_host_notifier_no_poll(VirtQueue *vq, AioContext *ct void virtio_queue_aio_detach_host_notifier(VirtQueue *vq, AioContext *ctx) { aio_set_event_notifier(ctx, &vq->host_notifier, true, NULL, NULL, NULL); - /* Test and clear notifier before after disabling event, - * in case poll callback didn't have time to run. */ - virtio_queue_host_notifier_read(&vq->host_notifier); } void virtio_queue_host_notifier_read(EventNotifier *n)