--- /dev/null
+/*
+ * Dedicated thread for virtio-blk I/O processing
+ *
+ * Copyright 2012 IBM, Corp.
+ * Copyright 2012 Red Hat, Inc. and/or its affiliates
+ *
+ * Authors:
+ * Stefan Hajnoczi <stefanha@redhat.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ *
+ */
+
+#include "trace.h"
+#include "qemu/iov.h"
+#include "qemu/thread.h"
+#include "qemu/error-report.h"
+#include "hw/virtio/virtio-access.h"
+#include "hw/virtio/dataplane/vring.h"
+#include "hw/virtio/dataplane/vring-accessors.h"
+#include "sysemu/block-backend.h"
+#include "hw/virtio/virtio-blk.h"
+#include "virtio-blk.h"
+#include "block/aio.h"
+#include "hw/virtio/virtio-bus.h"
+#include "qom/object_interfaces.h"
+
+struct VirtIOBlockDataPlane {
+ bool started;
+ bool starting;
+ bool stopping;
+ bool disabled;
+
+ VirtIOBlkConf *conf;
+
+ VirtIODevice *vdev;
+ Vring vring; /* virtqueue vring */
+ EventNotifier *guest_notifier; /* irq */
+ QEMUBH *bh; /* bh for guest notification */
+
+ /* Note that these EventNotifiers are assigned by value. This is
+ * fine as long as you do not call event_notifier_cleanup on them
+ * (because you don't own the file descriptor or handle; you just
+ * use it).
+ */
+ IOThread *iothread;
+ IOThread internal_iothread_obj;
+ AioContext *ctx;
+ EventNotifier host_notifier; /* doorbell */
+
+ /* Operation blocker on BDS */
+ Error *blocker;
+ void (*saved_complete_request)(struct VirtIOBlockReq *req,
+ unsigned char status);
+};
+
+/* Raise an interrupt to signal guest, if necessary */
+static void notify_guest(VirtIOBlockDataPlane *s)
+{
+ if (!vring_should_notify(s->vdev, &s->vring)) {
+ return;
+ }
+
+ event_notifier_set(s->guest_notifier);
+}
+
+static void notify_guest_bh(void *opaque)
+{
+ VirtIOBlockDataPlane *s = opaque;
+
+ notify_guest(s);
+}
+
+static void complete_request_vring(VirtIOBlockReq *req, unsigned char status)
+{
+ VirtIOBlockDataPlane *s = req->dev->dataplane;
+ stb_p(&req->in->status, status);
+
+ vring_push(s->vdev, &req->dev->dataplane->vring, &req->elem, req->in_len);
+
+ /* Suppress notification to guest by BH and its scheduled
+ * flag because requests are completed as a batch after io
+ * plug & unplug is introduced, and the BH can still be
+ * executed in dataplane aio context even after it is
+ * stopped, so needn't worry about notification loss with BH.
+ */
+ qemu_bh_schedule(s->bh);
+}
+
+static void handle_notify(EventNotifier *e)
+{
+ VirtIOBlockDataPlane *s = container_of(e, VirtIOBlockDataPlane,
+ host_notifier);
+ VirtIOBlock *vblk = VIRTIO_BLK(s->vdev);
+
+ event_notifier_test_and_clear(&s->host_notifier);
+ blk_io_plug(s->conf->conf.blk);
+ for (;;) {
+ MultiReqBuffer mrb = {};
+ int ret;
+
+ /* Disable guest->host notifies to avoid unnecessary vmexits */
+ vring_disable_notification(s->vdev, &s->vring);
+
+ for (;;) {
+ VirtIOBlockReq *req = virtio_blk_alloc_request(vblk);
+
+ ret = vring_pop(s->vdev, &s->vring, &req->elem);
+ if (ret < 0) {
+ virtio_blk_free_request(req);
+ break; /* no more requests */
+ }
+
+ trace_virtio_blk_data_plane_process_request(s, req->elem.out_num,
+ req->elem.in_num,
+ req->elem.index);
+
+ virtio_blk_handle_request(req, &mrb);
+ }
+
+ if (mrb.num_reqs) {
+ virtio_blk_submit_multireq(s->conf->conf.blk, &mrb);
+ }
+
+ if (likely(ret == -EAGAIN)) { /* vring emptied */
+ /* Re-enable guest->host notifies and stop processing the vring.
+ * But if the guest has snuck in more descriptors, keep processing.
+ */
+ if (vring_enable_notification(s->vdev, &s->vring)) {
+ break;
+ }
+ } else { /* fatal error */
+ break;
+ }
+ }
+ blk_io_unplug(s->conf->conf.blk);
+}
+
+/* Context: QEMU global mutex held */
+void virtio_blk_data_plane_create(VirtIODevice *vdev, VirtIOBlkConf *conf,
+ VirtIOBlockDataPlane **dataplane,
+ Error **errp)
+{
+ VirtIOBlockDataPlane *s;
+ Error *local_err = NULL;
+ BusState *qbus = BUS(qdev_get_parent_bus(DEVICE(vdev)));
+ VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
+
+ *dataplane = NULL;
+
+ if (!conf->data_plane && !conf->iothread) {
+ return;
+ }
+
+ /* Don't try if transport does not support notifiers. */
+ if (!k->set_guest_notifiers || !k->set_host_notifier) {
+ error_setg(errp,
+ "device is incompatible with x-data-plane "
+ "(transport does not support notifiers)");
+ return;
+ }
+
+ /* If dataplane is (re-)enabled while the guest is running there could be
+ * block jobs that can conflict.
+ */
+ if (blk_op_is_blocked(conf->conf.blk, BLOCK_OP_TYPE_DATAPLANE,
+ &local_err)) {
+ error_setg(errp, "cannot start dataplane thread: %s",
+ error_get_pretty(local_err));
+ error_free(local_err);
+ return;
+ }
+
+ s = g_new0(VirtIOBlockDataPlane, 1);
+ s->vdev = vdev;
+ s->conf = conf;
+
+ if (conf->iothread) {
+ s->iothread = conf->iothread;
+ object_ref(OBJECT(s->iothread));
+ } else {
+ /* Create per-device IOThread if none specified. This is for
+ * x-data-plane option compatibility. If x-data-plane is removed we
+ * can drop this.
+ */
+ object_initialize(&s->internal_iothread_obj,
+ sizeof(s->internal_iothread_obj),
+ TYPE_IOTHREAD);
+ user_creatable_complete(OBJECT(&s->internal_iothread_obj), &error_abort);
+ s->iothread = &s->internal_iothread_obj;
+ }
+ s->ctx = iothread_get_aio_context(s->iothread);
+ s->bh = aio_bh_new(s->ctx, notify_guest_bh, s);
+
+ error_setg(&s->blocker, "block device is in use by data plane");
+ blk_op_block_all(conf->conf.blk, s->blocker);
+ blk_op_unblock(conf->conf.blk, BLOCK_OP_TYPE_RESIZE, s->blocker);
+ blk_op_unblock(conf->conf.blk, BLOCK_OP_TYPE_DRIVE_DEL, s->blocker);
+ blk_op_unblock(conf->conf.blk, BLOCK_OP_TYPE_BACKUP_SOURCE, s->blocker);
+ blk_op_unblock(conf->conf.blk, BLOCK_OP_TYPE_CHANGE, s->blocker);
+ blk_op_unblock(conf->conf.blk, BLOCK_OP_TYPE_COMMIT_SOURCE, s->blocker);
+ blk_op_unblock(conf->conf.blk, BLOCK_OP_TYPE_COMMIT_TARGET, s->blocker);
+ blk_op_unblock(conf->conf.blk, BLOCK_OP_TYPE_EJECT, s->blocker);
+ blk_op_unblock(conf->conf.blk, BLOCK_OP_TYPE_EXTERNAL_SNAPSHOT, s->blocker);
+ blk_op_unblock(conf->conf.blk, BLOCK_OP_TYPE_INTERNAL_SNAPSHOT, s->blocker);
+ blk_op_unblock(conf->conf.blk, BLOCK_OP_TYPE_INTERNAL_SNAPSHOT_DELETE,
+ s->blocker);
+ blk_op_unblock(conf->conf.blk, BLOCK_OP_TYPE_MIRROR, s->blocker);
+ blk_op_unblock(conf->conf.blk, BLOCK_OP_TYPE_STREAM, s->blocker);
+ blk_op_unblock(conf->conf.blk, BLOCK_OP_TYPE_REPLACE, s->blocker);
+
+ *dataplane = s;
+}
+
+/* Context: QEMU global mutex held */
+void virtio_blk_data_plane_destroy(VirtIOBlockDataPlane *s)
+{
+ if (!s) {
+ return;
+ }
+
+ virtio_blk_data_plane_stop(s);
+ blk_op_unblock_all(s->conf->conf.blk, s->blocker);
+ error_free(s->blocker);
+ qemu_bh_delete(s->bh);
+ object_unref(OBJECT(s->iothread));
+ g_free(s);
+}
+
+/* Context: QEMU global mutex held */
+void virtio_blk_data_plane_start(VirtIOBlockDataPlane *s)
+{
+ BusState *qbus = BUS(qdev_get_parent_bus(DEVICE(s->vdev)));
+ VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
+ VirtIOBlock *vblk = VIRTIO_BLK(s->vdev);
+ VirtQueue *vq;
+ int r;
+
+ if (s->started || s->disabled) {
+ return;
+ }
+
+ if (s->starting) {
+ return;
+ }
+
+ s->starting = true;
+
+ vq = virtio_get_queue(s->vdev, 0);
+ if (!vring_setup(&s->vring, s->vdev, 0)) {
+ goto fail_vring;
+ }
+
+ /* Set up guest notifier (irq) */
+ r = k->set_guest_notifiers(qbus->parent, 1, true);
+ if (r != 0) {
+ fprintf(stderr, "virtio-blk failed to set guest notifier (%d), "
+ "ensure -enable-kvm is set\n", r);
+ goto fail_guest_notifiers;
+ }
+ s->guest_notifier = virtio_queue_get_guest_notifier(vq);
+
+ /* Set up virtqueue notify */
+ r = k->set_host_notifier(qbus->parent, 0, true);
+ if (r != 0) {
+ fprintf(stderr, "virtio-blk failed to set host notifier (%d)\n", r);
+ goto fail_host_notifier;
+ }
+ s->host_notifier = *virtio_queue_get_host_notifier(vq);
+
+ s->saved_complete_request = vblk->complete_request;
+ vblk->complete_request = complete_request_vring;
+
+ s->starting = false;
+ s->started = true;
+ trace_virtio_blk_data_plane_start(s);
+
+ blk_set_aio_context(s->conf->conf.blk, s->ctx);
+
+ /* Kick right away to begin processing requests already in vring */
+ event_notifier_set(virtio_queue_get_host_notifier(vq));
+
+ /* Get this show started by hooking up our callbacks */
+ aio_context_acquire(s->ctx);
+ aio_set_event_notifier(s->ctx, &s->host_notifier, handle_notify);
+ aio_context_release(s->ctx);
+ return;
+
+ fail_host_notifier:
+ k->set_guest_notifiers(qbus->parent, 1, false);
+ fail_guest_notifiers:
+ vring_teardown(&s->vring, s->vdev, 0);
+ s->disabled = true;
+ fail_vring:
+ s->starting = false;
+}
+
+/* Context: QEMU global mutex held */
+void virtio_blk_data_plane_stop(VirtIOBlockDataPlane *s)
+{
+ BusState *qbus = BUS(qdev_get_parent_bus(DEVICE(s->vdev)));
+ VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
+ VirtIOBlock *vblk = VIRTIO_BLK(s->vdev);
+
+
+ /* Better luck next time. */
+ if (s->disabled) {
+ s->disabled = false;
+ return;
+ }
+ if (!s->started || s->stopping) {
+ return;
+ }
+ s->stopping = true;
+ vblk->complete_request = s->saved_complete_request;
+ trace_virtio_blk_data_plane_stop(s);
+
+ aio_context_acquire(s->ctx);
+
+ /* Stop notifications for new requests from guest */
+ aio_set_event_notifier(s->ctx, &s->host_notifier, NULL);
+
+ /* Drain and switch bs back to the QEMU main loop */
+ blk_set_aio_context(s->conf->conf.blk, qemu_get_aio_context());
+
+ aio_context_release(s->ctx);
+
+ /* Sync vring state back to virtqueue so that non-dataplane request
+ * processing can continue when we disable the host notifier below.
+ */
+ vring_teardown(&s->vring, s->vdev, 0);
+
+ k->set_host_notifier(qbus->parent, 0, false);
+
+ /* Clean up guest notifier (irq) */
+ k->set_guest_notifiers(qbus->parent, 1, false);
+
+ s->started = false;
+ s->stopping = false;
+}
Code Review / kvmfornfv.git / blobdiff