hw/block/dataplane/virtio-blk.c

   1 /*
   2  * Dedicated thread for virtio-blk I/O processing
   3  *
   4  * Copyright 2012 IBM, Corp.
   5  * Copyright 2012 Red Hat, Inc. and/or its affiliates
   6  *
   7  * Authors:
   8  *   Stefan Hajnoczi <stefanha@redhat.com>
   9  *
  10  * This work is licensed under the terms of the GNU GPL, version 2 or later.
  11  * See the COPYING file in the top-level directory.
  12  *
  13  */
  14
  15 #include "qemu/osdep.h"
  16 #include "qapi/error.h"
  17 #include "trace.h"
  18 #include "qemu/iov.h"
  19 #include "qemu/thread.h"
  20 #include "qemu/error-report.h"
  21 #include "hw/virtio/virtio-access.h"
  22 #include "sysemu/block-backend.h"
  23 #include "hw/virtio/virtio-blk.h"
  24 #include "virtio-blk.h"
  25 #include "block/aio.h"
  26 #include "hw/virtio/virtio-bus.h"
  27 #include "qom/object_interfaces.h"
  28
  29 struct VirtIOBlockDataPlane {
  30     bool starting;
  31     bool stopping;
  32
  33     VirtIOBlkConf *conf;
  34
  35     VirtIODevice *vdev;
  36     VirtQueue *vq;                  /* virtqueue vring */
  37     EventNotifier *guest_notifier;  /* irq */
  38     QEMUBH *bh;                     /* bh for guest notification */
  39
  40     /* Note that these EventNotifiers are assigned by value.  This is
  41      * fine as long as you do not call event_notifier_cleanup on them
  42      * (because you don't own the file descriptor or handle; you just
  43      * use it).
  44      */
  45     IOThread *iothread;
  46     AioContext *ctx;
  47 };
  48
  49 /* Raise an interrupt to signal guest, if necessary */
  50 void virtio_blk_data_plane_notify(VirtIOBlockDataPlane *s)
  51 {
  52     qemu_bh_schedule(s->bh);
  53 }
  54
  55 static void notify_guest_bh(void *opaque)
  56 {
  57     VirtIOBlockDataPlane *s = opaque;
  58
  59     if (!virtio_should_notify(s->vdev, s->vq)) {
  60         return;
  61     }
  62
  63     event_notifier_set(s->guest_notifier);
  64 }
  65
  66 /* Context: QEMU global mutex held */
  67 void virtio_blk_data_plane_create(VirtIODevice *vdev, VirtIOBlkConf *conf,
  68                                   VirtIOBlockDataPlane **dataplane,
  69                                   Error **errp)
  70 {
  71     VirtIOBlockDataPlane *s;
  72     BusState *qbus = BUS(qdev_get_parent_bus(DEVICE(vdev)));
  73     VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
  74
  75     *dataplane = NULL;
  76
  77     if (!conf->iothread) {
  78         return;
  79     }
  80
  81     /* Don't try if transport does not support notifiers. */
  82     if (!k->set_guest_notifiers || !k->ioeventfd_started) {
  83         error_setg(errp,
  84                    "device is incompatible with dataplane "
  85                    "(transport does not support notifiers)");
  86         return;
  87     }
  88
  89     /* If dataplane is (re-)enabled while the guest is running there could be
  90      * block jobs that can conflict.
  91      */
  92     if (blk_op_is_blocked(conf->conf.blk, BLOCK_OP_TYPE_DATAPLANE, errp)) {
  93         error_prepend(errp, "cannot start dataplane thread: ");
  94         return;
  95     }
  96
  97     s = g_new0(VirtIOBlockDataPlane, 1);
  98     s->vdev = vdev;
  99     s->conf = conf;
 100
 101     if (conf->iothread) {
 102         s->iothread = conf->iothread;
 103         object_ref(OBJECT(s->iothread));
 104     }
 105     s->ctx = iothread_get_aio_context(s->iothread);
 106     s->bh = aio_bh_new(s->ctx, notify_guest_bh, s);
 107
 108     *dataplane = s;
 109 }
 110
 111 /* Context: QEMU global mutex held */
 112 void virtio_blk_data_plane_destroy(VirtIOBlockDataPlane *s)
 113 {
 114     if (!s) {
 115         return;
 116     }
 117
 118     virtio_blk_data_plane_stop(s);
 119     qemu_bh_delete(s->bh);
 120     object_unref(OBJECT(s->iothread));
 121     g_free(s);
 122 }
 123
 124 static void virtio_blk_data_plane_handle_output(VirtIODevice *vdev,
 125                                                 VirtQueue *vq)
 126 {
 127     VirtIOBlock *s = (VirtIOBlock *)vdev;
 128
 129     assert(s->dataplane);
 130     assert(s->dataplane_started);
 131
 132     virtio_blk_handle_vq(s, vq);
 133 }
 134
 135 /* Context: QEMU global mutex held */
 136 void virtio_blk_data_plane_start(VirtIOBlockDataPlane *s)
 137 {
 138     BusState *qbus = BUS(qdev_get_parent_bus(DEVICE(s->vdev)));
 139     VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
 140     VirtIOBlock *vblk = VIRTIO_BLK(s->vdev);
 141     int r;
 142
 143     if (vblk->dataplane_started || s->starting) {
 144         return;
 145     }
 146
 147     s->starting = true;
 148     s->vq = virtio_get_queue(s->vdev, 0);
 149
 150     /* Set up guest notifier (irq) */
 151     r = k->set_guest_notifiers(qbus->parent, 1, true);
 152     if (r != 0) {
 153         fprintf(stderr, "virtio-blk failed to set guest notifier (%d), "
 154                 "ensure -enable-kvm is set\n", r);
 155         goto fail_guest_notifiers;
 156     }
 157     s->guest_notifier = virtio_queue_get_guest_notifier(s->vq);
 158
 159     /* Set up virtqueue notify */
 160     r = virtio_bus_set_host_notifier(VIRTIO_BUS(qbus), 0, true);
 161     if (r != 0) {
 162         fprintf(stderr, "virtio-blk failed to set host notifier (%d)\n", r);
 163         goto fail_host_notifier;
 164     }
 165
 166     s->starting = false;
 167     vblk->dataplane_started = true;
 168     trace_virtio_blk_data_plane_start(s);
 169
 170     blk_set_aio_context(s->conf->conf.blk, s->ctx);
 171
 172     /* Kick right away to begin processing requests already in vring */
 173     event_notifier_set(virtio_queue_get_host_notifier(s->vq));
 174
 175     /* Get this show started by hooking up our callbacks */
 176     aio_context_acquire(s->ctx);
 177     virtio_queue_aio_set_host_notifier_handler(s->vq, s->ctx,
 178                                                virtio_blk_data_plane_handle_output);
 179     aio_context_release(s->ctx);
 180     return;
 181
 182   fail_host_notifier:
 183     k->set_guest_notifiers(qbus->parent, 1, false);
 184   fail_guest_notifiers:
 185     vblk->dataplane_disabled = true;
 186     s->starting = false;
 187     vblk->dataplane_started = true;
 188 }
 189
 190 /* Context: QEMU global mutex held */
 191 void virtio_blk_data_plane_stop(VirtIOBlockDataPlane *s)
 192 {
 193     BusState *qbus = BUS(qdev_get_parent_bus(DEVICE(s->vdev)));
 194     VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
 195     VirtIOBlock *vblk = VIRTIO_BLK(s->vdev);
 196
 197     if (!vblk->dataplane_started || s->stopping) {
 198         return;
 199     }
 200
 201     /* Better luck next time. */
 202     if (vblk->dataplane_disabled) {
 203         vblk->dataplane_disabled = false;
 204         vblk->dataplane_started = false;
 205         return;
 206     }
 207     s->stopping = true;
 208     trace_virtio_blk_data_plane_stop(s);
 209
 210     aio_context_acquire(s->ctx);
 211
 212     /* Stop notifications for new requests from guest */
 213     virtio_queue_aio_set_host_notifier_handler(s->vq, s->ctx, NULL);
 214
 215     /* Drain and switch bs back to the QEMU main loop */
 216     blk_set_aio_context(s->conf->conf.blk, qemu_get_aio_context());
 217
 218     aio_context_release(s->ctx);
 219
 220     virtio_bus_set_host_notifier(VIRTIO_BUS(qbus), 0, false);
 221
 222     /* Clean up guest notifier (irq) */
 223     k->set_guest_notifiers(qbus->parent, 1, false);
 224
 225     vblk->dataplane_started = false;
 226     s->stopping = false;
 227 }