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The kernel is dropping it in favour of the mainstream worker ioctls, which vhost-blk now supports, so use those: create num-threads - 1 workers with VHOST_NEW_WORKER and attach them to the virtqueues round-robin with VHOST_ATTACH_VRING_WORKER, the default worker being the first one. This is the layout VHOST_SET_NWORKERS produced. VHOST_NEW_WORKER works only in vhost_task mode, while our kernel, unlike mainline, defaults to kthreads, so switch the device to vhost_task mode with VHOST_SET_FORK_FROM_OWNER before VHOST_SET_OWNER. VHOST_RESET_OWNER restores the default, hence this is done on every start. With num-threads=1 nothing changes: no worker ioctls, kthread mode. On a kernel without these ioctls warn and run a single thread rather than fail to start vhost-blk. https://virtuozzo.atlassian.net/browse/VSTOR-107537 Signed-off-by: Alexander Ivanov --- hw/block/vhost-blk.c | 76 +++++++++++++++++++++++++++++++++++++++++--- 1 file changed, 72 insertions(+), 4 deletions(-) diff --git a/hw/block/vhost-blk.c b/hw/block/vhost-blk.c index abddff02c6d..7b427083478 100644 --- a/hw/block/vhost-blk.c +++ b/hw/block/vhost-blk.c @@ -33,6 +33,52 @@ #include "migration/cpr.h" #include "system/runstate.h" +/* + * Spread the virtqueues round-robin over num-threads workers, the first one + * being the default worker that VHOST_SET_OWNER created. + */ +static int vhost_blk_set_workers(VHostBlk *s, int nworkers) +{ + uint32_t ids[VHOST_BLK_MAX_QUEUES]; + struct vhost_worker_state worker; + struct vhost_vring_worker vq_worker; + int ret, i; + + nworkers = MIN(nworkers, VHOST_BLK_MAX_QUEUES); + for (i = 1; i < nworkers; i++) { + memset(&worker, 0, sizeof(worker)); + if (ioctl(s->vhostfd, VHOST_NEW_WORKER, &worker)) { + ret = -errno; + if (ret == -ENOTTY && i == 1) { + warn_report_once("vhost-blk: kernel does not support worker " + "ioctls, using a single kernel thread"); + return 0; + } + error_report("vhost-blk: unable to create kernel thread: %s", + strerror(-ret)); + return ret; + } + ids[i] = worker.worker_id; + } + + for (i = 0; i < s->dev.nvqs; i++) { + if (i % nworkers == 0) { + continue; + } + memset(&vq_worker, 0, sizeof(vq_worker)); + vq_worker.index = i; + vq_worker.worker_id = ids[i % nworkers]; + if (ioctl(s->vhostfd, VHOST_ATTACH_VRING_WORKER, &vq_worker)) { + ret = -errno; + error_report("vhost-blk: unable to attach kernel thread to " + "queue %d: %s", i, strerror(-ret)); + return ret; + } + } + + return 0; +} + static int vhost_blk_start(VirtIODevice *vdev) { VHostBlk *s = VHOST_BLK(vdev); @@ -51,15 +97,37 @@ static int vhost_blk_start(VirtIODevice *vdev) return 0; } + nworkers = MIN(s->conf.num_threads, s->dev.nvqs); + if (nworkers > 1) { + /* + * VHOST_NEW_WORKER works only in vhost_task mode, and + * VHOST_RESET_OWNER brings the kthread default back. + */ + uint8_t fork_owner = VHOST_FORK_OWNER_TASK; + + if (ioctl(s->vhostfd, VHOST_SET_FORK_FROM_OWNER, &fork_owner)) { + ret = -errno; + if (ret != -ENOTTY) { + error_report("vhost-blk: unable to set vhost task mode: %s", + strerror(-ret)); + return ret; + } + warn_report_once("vhost-blk: kernel does not support vhost " + "tasks, using a single kernel thread"); + nworkers = 1; + } + } + if (ioctl(s->vhostfd, VHOST_SET_OWNER, NULL)) { error_report("vhost-blk: unable to set owner"); return -ENOSYS; } - nworkers = s->conf.num_threads; - if (nworkers != 1 && ioctl(s->vhostfd, VHOST_SET_NWORKERS, &nworkers)) { - error_report("vhost-blk: unable to set number of kernel threads"); - return -EINVAL; + if (nworkers > 1) { + ret = vhost_blk_set_workers(s, nworkers); + if (ret < 0) { + return ret; + } } if (s->conf.serial) { -- 2.53.0