blob: b28d81737ef5ef077ab7a656f874bdeb8dd6c019 [file] [log] [blame]
/*
* 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 "qemu/osdep.h"
#include "qapi/error.h"
#include "trace.h"
#include "qemu/iov.h"
#include "qemu/main-loop.h"
#include "qemu/thread.h"
#include "qemu/error-report.h"
#include "hw/virtio/virtio-access.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 starting;
bool stopping;
VirtIOBlkConf *conf;
VirtIODevice *vdev;
QEMUBH *bh; /* bh for guest notification */
unsigned long *batch_notify_vqs;
bool batch_notifications;
/* 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;
AioContext *ctx;
};
/* Raise an interrupt to signal guest, if necessary */
void virtio_blk_data_plane_notify(VirtIOBlockDataPlane *s, VirtQueue *vq)
{
if (s->batch_notifications) {
set_bit(virtio_get_queue_index(vq), s->batch_notify_vqs);
qemu_bh_schedule(s->bh);
} else {
virtio_notify_irqfd(s->vdev, vq);
}
}
static void notify_guest_bh(void *opaque)
{
VirtIOBlockDataPlane *s = opaque;
unsigned nvqs = s->conf->num_queues;
unsigned long bitmap[BITS_TO_LONGS(nvqs)];
unsigned j;
memcpy(bitmap, s->batch_notify_vqs, sizeof(bitmap));
memset(s->batch_notify_vqs, 0, sizeof(bitmap));
for (j = 0; j < nvqs; j += BITS_PER_LONG) {
unsigned long bits = bitmap[j / BITS_PER_LONG];
while (bits != 0) {
unsigned i = j + ctzl(bits);
VirtQueue *vq = virtio_get_queue(s->vdev, i);
virtio_notify_irqfd(s->vdev, vq);
bits &= bits - 1; /* clear right-most bit */
}
}
}
/* Context: QEMU global mutex held */
bool virtio_blk_data_plane_create(VirtIODevice *vdev, VirtIOBlkConf *conf,
VirtIOBlockDataPlane **dataplane,
Error **errp)
{
VirtIOBlockDataPlane *s;
BusState *qbus = BUS(qdev_get_parent_bus(DEVICE(vdev)));
VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
*dataplane = NULL;
if (conf->iothread) {
if (!k->set_guest_notifiers || !k->ioeventfd_assign) {
error_setg(errp,
"device is incompatible with iothread "
"(transport does not support notifiers)");
return false;
}
if (!virtio_device_ioeventfd_enabled(vdev)) {
error_setg(errp, "ioeventfd is required for iothread");
return false;
}
/* 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, errp)) {
error_prepend(errp, "cannot start virtio-blk dataplane: ");
return false;
}
}
/* Don't try if transport does not support notifiers. */
if (!virtio_device_ioeventfd_enabled(vdev)) {
return false;
}
s = g_new0(VirtIOBlockDataPlane, 1);
s->vdev = vdev;
s->conf = conf;
if (conf->iothread) {
s->iothread = conf->iothread;
object_ref(OBJECT(s->iothread));
s->ctx = iothread_get_aio_context(s->iothread);
} else {
s->ctx = qemu_get_aio_context();
}
s->bh = aio_bh_new(s->ctx, notify_guest_bh, s);
s->batch_notify_vqs = bitmap_new(conf->num_queues);
*dataplane = s;
return true;
}
/* Context: QEMU global mutex held */
void virtio_blk_data_plane_destroy(VirtIOBlockDataPlane *s)
{
VirtIOBlock *vblk;
if (!s) {
return;
}
vblk = VIRTIO_BLK(s->vdev);
assert(!vblk->dataplane_started);
g_free(s->batch_notify_vqs);
qemu_bh_delete(s->bh);
if (s->iothread) {
object_unref(OBJECT(s->iothread));
}
g_free(s);
}
/* Context: QEMU global mutex held */
int virtio_blk_data_plane_start(VirtIODevice *vdev)
{
VirtIOBlock *vblk = VIRTIO_BLK(vdev);
VirtIOBlockDataPlane *s = vblk->dataplane;
BusState *qbus = BUS(qdev_get_parent_bus(DEVICE(vblk)));
VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
AioContext *old_context;
unsigned i;
unsigned nvqs = s->conf->num_queues;
Error *local_err = NULL;
int r;
if (vblk->dataplane_started || s->starting) {
return 0;
}
s->starting = true;
if (!virtio_vdev_has_feature(vdev, VIRTIO_RING_F_EVENT_IDX)) {
s->batch_notifications = true;
} else {
s->batch_notifications = false;
}
/* Set up guest notifier (irq) */
r = k->set_guest_notifiers(qbus->parent, nvqs, true);
if (r != 0) {
error_report("virtio-blk failed to set guest notifier (%d), "
"ensure -accel kvm is set.", r);
goto fail_guest_notifiers;
}
/*
* Batch all the host notifiers in a single transaction to avoid
* quadratic time complexity in address_space_update_ioeventfds().
*/
memory_region_transaction_begin();
/* Set up virtqueue notify */
for (i = 0; i < nvqs; i++) {
r = virtio_bus_set_host_notifier(VIRTIO_BUS(qbus), i, true);
if (r != 0) {
int j = i;
fprintf(stderr, "virtio-blk failed to set host notifier (%d)\n", r);
while (i--) {
virtio_bus_set_host_notifier(VIRTIO_BUS(qbus), i, false);
}
/*
* The transaction expects the ioeventfds to be open when it
* commits. Do it now, before the cleanup loop.
*/
memory_region_transaction_commit();
while (j--) {
virtio_bus_cleanup_host_notifier(VIRTIO_BUS(qbus), j);
}
goto fail_host_notifiers;
}
}
memory_region_transaction_commit();
/*
* These fields are visible to the IOThread so we rely on implicit barriers
* in aio_context_acquire() on the write side and aio_notify_accept() on
* the read side.
*/
s->starting = false;
vblk->dataplane_started = true;
trace_virtio_blk_data_plane_start(s);
old_context = blk_get_aio_context(s->conf->conf.blk);
aio_context_acquire(old_context);
r = blk_set_aio_context(s->conf->conf.blk, s->ctx, &local_err);
aio_context_release(old_context);
if (r < 0) {
error_report_err(local_err);
goto fail_aio_context;
}
/* Kick right away to begin processing requests already in vring */
for (i = 0; i < nvqs; i++) {
VirtQueue *vq = virtio_get_queue(s->vdev, i);
event_notifier_set(virtio_queue_get_host_notifier(vq));
}
/* Get this show started by hooking up our callbacks */
aio_context_acquire(s->ctx);
for (i = 0; i < nvqs; i++) {
VirtQueue *vq = virtio_get_queue(s->vdev, i);
virtio_queue_aio_attach_host_notifier(vq, s->ctx);
}
aio_context_release(s->ctx);
return 0;
fail_aio_context:
memory_region_transaction_begin();
for (i = 0; i < nvqs; i++) {
virtio_bus_set_host_notifier(VIRTIO_BUS(qbus), i, false);
}
memory_region_transaction_commit();
for (i = 0; i < nvqs; i++) {
virtio_bus_cleanup_host_notifier(VIRTIO_BUS(qbus), i);
}
fail_host_notifiers:
k->set_guest_notifiers(qbus->parent, nvqs, false);
fail_guest_notifiers:
vblk->dataplane_disabled = true;
s->starting = false;
vblk->dataplane_started = true;
return -ENOSYS;
}
/* Stop notifications for new requests from guest.
*
* Context: BH in IOThread
*/
static void virtio_blk_data_plane_stop_bh(void *opaque)
{
VirtIOBlockDataPlane *s = opaque;
unsigned i;
for (i = 0; i < s->conf->num_queues; i++) {
VirtQueue *vq = virtio_get_queue(s->vdev, i);
virtio_queue_aio_detach_host_notifier(vq, s->ctx);
}
}
/* Context: QEMU global mutex held */
void virtio_blk_data_plane_stop(VirtIODevice *vdev)
{
VirtIOBlock *vblk = VIRTIO_BLK(vdev);
VirtIOBlockDataPlane *s = vblk->dataplane;
BusState *qbus = qdev_get_parent_bus(DEVICE(vblk));
VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
unsigned i;
unsigned nvqs = s->conf->num_queues;
if (!vblk->dataplane_started || s->stopping) {
return;
}
/* Better luck next time. */
if (vblk->dataplane_disabled) {
vblk->dataplane_disabled = false;
vblk->dataplane_started = false;
return;
}
s->stopping = true;
trace_virtio_blk_data_plane_stop(s);
aio_context_acquire(s->ctx);
aio_wait_bh_oneshot(s->ctx, virtio_blk_data_plane_stop_bh, s);
/* Wait for virtio_blk_dma_restart_bh() and in flight I/O to complete */
blk_drain(s->conf->conf.blk);
/*
* Try to switch bs back to the QEMU main loop. If other users keep the
* BlockBackend in the iothread, that's ok
*/
blk_set_aio_context(s->conf->conf.blk, qemu_get_aio_context(), NULL);
aio_context_release(s->ctx);
/*
* Batch all the host notifiers in a single transaction to avoid
* quadratic time complexity in address_space_update_ioeventfds().
*/
memory_region_transaction_begin();
for (i = 0; i < nvqs; i++) {
virtio_bus_set_host_notifier(VIRTIO_BUS(qbus), i, false);
}
/*
* The transaction expects the ioeventfds to be open when it
* commits. Do it now, before the cleanup loop.
*/
memory_region_transaction_commit();
for (i = 0; i < nvqs; i++) {
virtio_bus_cleanup_host_notifier(VIRTIO_BUS(qbus), i);
}
qemu_bh_cancel(s->bh);
notify_guest_bh(s); /* final chance to notify guest */
/* Clean up guest notifier (irq) */
k->set_guest_notifiers(qbus->parent, nvqs, false);
vblk->dataplane_started = false;
s->stopping = false;
}