From d54e88103aa76f3bf755b3f4308d8ab60367c6ef Mon Sep 17 00:00:00 2001 From: Stefan Hajnoczi Date: Thu, 14 Sep 2023 10:00:59 -0400 Subject: [PATCH 074/101] virtio-blk: add lock to protect s->rq RH-Author: Kevin Wolf RH-MergeRequest: 214: Remove AioContext lock RH-Jira: RHEL-15965 RH-Acked-by: Miroslav Rezanina RH-Acked-by: Stefan Hajnoczi RH-Commit: [5/26] 17dcd5ba18c03e5633a014d8d62d34d8dd7b43bf (kmwolf/centos-qemu-kvm) s->rq is accessed from IO_CODE and GLOBAL_STATE_CODE. Introduce a lock to protect s->rq and eliminate reliance on the AioContext lock. Signed-off-by: Stefan Hajnoczi Message-ID: <20230914140101.1065008-3-stefanha@redhat.com> Reviewed-by: Kevin Wolf Reviewed-by: Eric Blake Reviewed-by: Michael S. Tsirkin Signed-off-by: Kevin Wolf --- hw/block/virtio-blk.c | 67 +++++++++++++++++++++++----------- include/hw/virtio/virtio-blk.h | 3 +- 2 files changed, 47 insertions(+), 23 deletions(-) diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c index a1f8e15522..ee38e089bc 100644 --- a/hw/block/virtio-blk.c +++ b/hw/block/virtio-blk.c @@ -82,8 +82,11 @@ static int virtio_blk_handle_rw_error(VirtIOBlockReq *req, int error, /* Break the link as the next request is going to be parsed from the * ring again. Otherwise we may end up doing a double completion! */ req->mr_next = NULL; - req->next = s->rq; - s->rq = req; + + WITH_QEMU_LOCK_GUARD(&s->rq_lock) { + req->next = s->rq; + s->rq = req; + } } else if (action == BLOCK_ERROR_ACTION_REPORT) { virtio_blk_req_complete(req, VIRTIO_BLK_S_IOERR); if (acct_failed) { @@ -1183,10 +1186,13 @@ static void virtio_blk_dma_restart_bh(void *opaque) { VirtIOBlock *s = opaque; - VirtIOBlockReq *req = s->rq; + VirtIOBlockReq *req; MultiReqBuffer mrb = {}; - s->rq = NULL; + WITH_QEMU_LOCK_GUARD(&s->rq_lock) { + req = s->rq; + s->rq = NULL; + } aio_context_acquire(blk_get_aio_context(s->conf.conf.blk)); while (req) { @@ -1238,22 +1244,29 @@ static void virtio_blk_reset(VirtIODevice *vdev) AioContext *ctx; VirtIOBlockReq *req; + /* Dataplane has stopped... */ + assert(!s->dataplane_started); + + /* ...but requests may still be in flight. */ ctx = blk_get_aio_context(s->blk); aio_context_acquire(ctx); blk_drain(s->blk); + aio_context_release(ctx); /* We drop queued requests after blk_drain() because blk_drain() itself can * produce them. */ - while (s->rq) { - req = s->rq; - s->rq = req->next; - virtqueue_detach_element(req->vq, &req->elem, 0); - virtio_blk_free_request(req); - } + WITH_QEMU_LOCK_GUARD(&s->rq_lock) { + while (s->rq) { + req = s->rq; + s->rq = req->next; - aio_context_release(ctx); + /* No other threads can access req->vq here */ + virtqueue_detach_element(req->vq, &req->elem, 0); + + virtio_blk_free_request(req); + } + } - assert(!s->dataplane_started); blk_set_enable_write_cache(s->blk, s->original_wce); } @@ -1443,18 +1456,22 @@ static void virtio_blk_set_status(VirtIODevice *vdev, uint8_t status) static void virtio_blk_save_device(VirtIODevice *vdev, QEMUFile *f) { VirtIOBlock *s = VIRTIO_BLK(vdev); - VirtIOBlockReq *req = s->rq; - while (req) { - qemu_put_sbyte(f, 1); + WITH_QEMU_LOCK_GUARD(&s->rq_lock) { + VirtIOBlockReq *req = s->rq; - if (s->conf.num_queues > 1) { - qemu_put_be32(f, virtio_get_queue_index(req->vq)); - } + while (req) { + qemu_put_sbyte(f, 1); - qemu_put_virtqueue_element(vdev, f, &req->elem); - req = req->next; + if (s->conf.num_queues > 1) { + qemu_put_be32(f, virtio_get_queue_index(req->vq)); + } + + qemu_put_virtqueue_element(vdev, f, &req->elem); + req = req->next; + } } + qemu_put_sbyte(f, 0); } @@ -1480,8 +1497,11 @@ static int virtio_blk_load_device(VirtIODevice *vdev, QEMUFile *f, req = qemu_get_virtqueue_element(vdev, f, sizeof(VirtIOBlockReq)); virtio_blk_init_request(s, virtio_get_queue(vdev, vq_idx), req); - req->next = s->rq; - s->rq = req; + + WITH_QEMU_LOCK_GUARD(&s->rq_lock) { + req->next = s->rq; + s->rq = req; + } } return 0; @@ -1628,6 +1648,8 @@ static void virtio_blk_device_realize(DeviceState *dev, Error **errp) s->host_features); virtio_init(vdev, VIRTIO_ID_BLOCK, s->config_size); + qemu_mutex_init(&s->rq_lock); + s->blk = conf->conf.blk; s->rq = NULL; s->sector_mask = (s->conf.conf.logical_block_size / BDRV_SECTOR_SIZE) - 1; @@ -1679,6 +1701,7 @@ static void virtio_blk_device_unrealize(DeviceState *dev) virtio_del_queue(vdev, i); } qemu_coroutine_dec_pool_size(conf->num_queues * conf->queue_size / 2); + qemu_mutex_destroy(&s->rq_lock); blk_ram_registrar_destroy(&s->blk_ram_registrar); qemu_del_vm_change_state_handler(s->change); blockdev_mark_auto_del(s->blk); diff --git a/include/hw/virtio/virtio-blk.h b/include/hw/virtio/virtio-blk.h index dafec432ce..9881009c22 100644 --- a/include/hw/virtio/virtio-blk.h +++ b/include/hw/virtio/virtio-blk.h @@ -54,7 +54,8 @@ struct VirtIOBlockReq; struct VirtIOBlock { VirtIODevice parent_obj; BlockBackend *blk; - void *rq; + QemuMutex rq_lock; + void *rq; /* protected by rq_lock */ VirtIOBlkConf conf; unsigned short sector_mask; bool original_wce; -- 2.39.3