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);
}
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);
*dataplane = s;
}
static void xen_block_handle_requests(XenBlockDataPlane *dataplane)
{
RING_IDX rc, rp;
XenBlockRequest *request;
int inflight_atstart = dataplane->requests_inflight;
int batched = 0;
dataplane->more_work = 0;
rc = dataplane->rings.common.req_cons;
rp = dataplane->rings.common.sring->req_prod;
xen_rmb(); /* Ensure we see queued requests up to 'rp'. */
/*
* If there was more than IO_PLUG_THRESHOLD requests in flight
* when we got here, this is an indication that there the bottleneck
* is below us, so it's worth beginning to batch up I/O requests
* rather than submitting them immediately. The maximum number
* of requests we're willing to batch is the number already in
* flight, so it can grow up to max_requests when the bottleneck
* is below us.
*/
if (inflight_atstart > IO_PLUG_THRESHOLD) {
blk_io_plug(dataplane->blk);
}
while (rc != rp) {
/* pull request from ring */
if (RING_REQUEST_CONS_OVERFLOW(&dataplane->rings.common, rc)) {
break;
}
request = xen_block_start_request(dataplane);
if (request == NULL) {
dataplane->more_work++;
break;
}
xen_block_get_request(dataplane, request, rc);
dataplane->rings.common.req_cons = ++rc;
/* parse them */
if (xen_block_parse_request(request) != 0) {
switch (request->req.operation) {
case BLKIF_OP_READ:
block_acct_invalid(blk_get_stats(dataplane->blk),
BLOCK_ACCT_READ);
break;
case BLKIF_OP_WRITE:
block_acct_invalid(blk_get_stats(dataplane->blk),
BLOCK_ACCT_WRITE);
break;
case BLKIF_OP_FLUSH_DISKCACHE:
block_acct_invalid(blk_get_stats(dataplane->blk),
BLOCK_ACCT_FLUSH);
default:
break;
};
if (xen_block_send_response(request)) {
Error *local_err = NULL;
xen_device_notify_event_channel(dataplane->xendev,
dataplane->event_channel,
&local_err);
if (local_err) {
error_report_err(local_err);
}
}
xen_block_release_request(request);
continue;
}
if (inflight_atstart > IO_PLUG_THRESHOLD &&
batched >= inflight_atstart) {
blk_io_unplug(dataplane->blk);
}
xen_block_do_aio(request);
if (inflight_atstart > IO_PLUG_THRESHOLD) {
if (batched >= inflight_atstart) {
blk_io_plug(dataplane->blk);
batched = 0;
} else {
batched++;
}
}
}
if (inflight_atstart > IO_PLUG_THRESHOLD) {
blk_io_unplug(dataplane->blk);
}
if (dataplane->more_work &&
dataplane->requests_inflight < dataplane->max_requests) {
qemu_bh_schedule(dataplane->bh);
}
}
