qemu/hw/block/dataplane/virtio-blk.c

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/*
* 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/dataplane/vring.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(&req->dev->dataplane->vring, &req->elem,
req->qiov.size + sizeof(*req->in));
/* 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 = {
.num_writes = 0,
};
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);
}
virtio_submit_multiwrite(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_COMMIT, 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);
object_unref(OBJECT(s->iothread));
qemu_bh_delete(s->bh);
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;
}