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 "hw/virtio/virtio-blk.h"
  23 #include "virtio-blk.h"
  24 #include "block/aio.h"
  25 #include "hw/virtio/virtio-bus.h"
  26 #include "qom/object_interfaces.h"
  27
  28 struct VirtIOBlockDataPlane {
  29     bool starting;
  30     bool stopping;
  31
  32     VirtIOBlkConf *conf;
  33     VirtIODevice *vdev;
  34     QEMUBH *bh;                     /* bh for guest notification */
  35     unsigned long *batch_notify_vqs;
  36     bool batch_notifications;
  37
  38     /* Note that these EventNotifiers are assigned by value.  This is
  39      * fine as long as you do not call event_notifier_cleanup on them
  40      * (because you don't own the file descriptor or handle; you just
  41      * use it).
  42      */
  43     IOThread *iothread;
  44     AioContext *ctx;
  45 };
  46
  47 /* Raise an interrupt to signal guest, if necessary */
  48 void virtio_blk_data_plane_notify(VirtIOBlockDataPlane *s, VirtQueue *vq)
  49 {
  50     if (s->batch_notifications) {
  51         set_bit(virtio_get_queue_index(vq), s->batch_notify_vqs);
  52         qemu_bh_schedule(s->bh);
  53     } else {
  54         virtio_notify_irqfd(s->vdev, vq);
  55     }
  56 }
  57
  58 static void notify_guest_bh(void *opaque)
  59 {
  60     VirtIOBlockDataPlane *s = opaque;
  61     unsigned nvqs = s->conf->num_queues;
  62     unsigned long bitmap[BITS_TO_LONGS(nvqs)];
  63     unsigned j;
  64
  65     memcpy(bitmap, s->batch_notify_vqs, sizeof(bitmap));
  66     memset(s->batch_notify_vqs, 0, sizeof(bitmap));
  67
  68     for (j = 0; j < nvqs; j += BITS_PER_LONG) {
  69         unsigned long bits = bitmap[j];
  70
  71         while (bits != 0) {
  72             unsigned i = j + ctzl(bits);
  73             VirtQueue *vq = virtio_get_queue(s->vdev, i);
  74
  75             virtio_notify_irqfd(s->vdev, vq);
  76
  77             bits &= bits - 1; /* clear right-most bit */
  78         }
  79     }
  80 }
  81
  82 /* Context: QEMU global mutex held */
  83 bool virtio_blk_data_plane_create(VirtIODevice *vdev, VirtIOBlkConf *conf,
  84                                   VirtIOBlockDataPlane **dataplane,
  85                                   Error **errp)
  86 {
  87     VirtIOBlockDataPlane *s;
  88     BusState *qbus = BUS(qdev_get_parent_bus(DEVICE(vdev)));
  89     VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
  90
  91     *dataplane = NULL;
  92
  93     if (conf->iothread) {
  94         if (!k->set_guest_notifiers || !k->ioeventfd_assign) {
  95             error_setg(errp,
  96                        "device is incompatible with iothread "
  97                        "(transport does not support notifiers)");
  98             return false;
  99         }
 100         if (!virtio_device_ioeventfd_enabled(vdev)) {
 101             error_setg(errp, "ioeventfd is required for iothread");
 102             return false;
 103         }
 104
 105         /* If dataplane is (re-)enabled while the guest is running there could
 106          * be block jobs that can conflict.
 107          */
 108         if (blk_op_is_blocked(conf->conf.blk, BLOCK_OP_TYPE_DATAPLANE, errp)) {
 109             error_prepend(errp, "cannot start virtio-blk dataplane: ");
 110             return false;
 111         }
 112     }
 113     /* Don't try if transport does not support notifiers. */
 114     if (!virtio_device_ioeventfd_enabled(vdev)) {
 115         return false;
 116     }
 117
 118     s = g_new0(VirtIOBlockDataPlane, 1);
 119     s->vdev = vdev;
 120     s->conf = conf;
 121
 122     if (conf->iothread) {
 123         s->iothread = conf->iothread;
 124         object_ref(OBJECT(s->iothread));
 125         s->ctx = iothread_get_aio_context(s->iothread);
 126     } else {
 127         s->ctx = qemu_get_aio_context();
 128     }
 129     s->bh = aio_bh_new(s->ctx, notify_guest_bh, s);
 130     s->batch_notify_vqs = bitmap_new(conf->num_queues);
 131
 132     *dataplane = s;
 133
 134     return true;
 135 }
 136
 137 /* Context: QEMU global mutex held */
 138 void virtio_blk_data_plane_destroy(VirtIOBlockDataPlane *s)
 139 {
 140     VirtIOBlock *vblk;
 141
 142     if (!s) {
 143         return;
 144     }
 145
 146     vblk = VIRTIO_BLK(s->vdev);
 147     assert(!vblk->dataplane_started);
 148     g_free(s->batch_notify_vqs);
 149     qemu_bh_delete(s->bh);
 150     if (s->iothread) {
 151         object_unref(OBJECT(s->iothread));
 152     }
 153     g_free(s);
 154 }
 155
 156 static bool virtio_blk_data_plane_handle_output(VirtIODevice *vdev,
 157                                                 VirtQueue *vq)
 158 {
 159     VirtIOBlock *s = (VirtIOBlock *)vdev;
 160
 161     assert(s->dataplane);
 162     assert(s->dataplane_started);
 163
 164     return virtio_blk_handle_vq(s, vq);
 165 }
 166
 167 /* Context: QEMU global mutex held */
 168 int virtio_blk_data_plane_start(VirtIODevice *vdev)
 169 {
 170     VirtIOBlock *vblk = VIRTIO_BLK(vdev);
 171     VirtIOBlockDataPlane *s = vblk->dataplane;
 172     BusState *qbus = BUS(qdev_get_parent_bus(DEVICE(vblk)));
 173     VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
 174     unsigned i;
 175     unsigned nvqs = s->conf->num_queues;
 176     Error *local_err = NULL;
 177     int r;
 178
 179     if (vblk->dataplane_started || s->starting) {
 180         return 0;
 181     }
 182
 183     s->starting = true;
 184
 185     if (!virtio_vdev_has_feature(vdev, VIRTIO_RING_F_EVENT_IDX)) {
 186         s->batch_notifications = true;
 187     } else {
 188         s->batch_notifications = false;
 189     }
 190
 191     /* Set up guest notifier (irq) */
 192     r = k->set_guest_notifiers(qbus->parent, nvqs, true);
 193     if (r != 0) {
 194         error_report("virtio-blk failed to set guest notifier (%d), "
 195                      "ensure -accel kvm is set.", r);
 196         goto fail_guest_notifiers;
 197     }
 198
 199     /* Set up virtqueue notify */
 200     for (i = 0; i < nvqs; i++) {
 201         r = virtio_bus_set_host_notifier(VIRTIO_BUS(qbus), i, true);
 202         if (r != 0) {
 203             fprintf(stderr, "virtio-blk failed to set host notifier (%d)\n", r);
 204             while (i--) {
 205                 virtio_bus_set_host_notifier(VIRTIO_BUS(qbus), i, false);
 206                 virtio_bus_cleanup_host_notifier(VIRTIO_BUS(qbus), i);
 207             }
 208             goto fail_guest_notifiers;
 209         }
 210     }
 211
 212     s->starting = false;
 213     vblk->dataplane_started = true;
 214     trace_virtio_blk_data_plane_start(s);
 215
 216     r = blk_set_aio_context(s->conf->conf.blk, s->ctx, &local_err);
 217     if (r < 0) {
 218         error_report_err(local_err);
 219         goto fail_guest_notifiers;
 220     }
 221
 222     /* Kick right away to begin processing requests already in vring */
 223     for (i = 0; i < nvqs; i++) {
 224         VirtQueue *vq = virtio_get_queue(s->vdev, i);
 225
 226         event_notifier_set(virtio_queue_get_host_notifier(vq));
 227     }
 228
 229     /* Get this show started by hooking up our callbacks */
 230     aio_context_acquire(s->ctx);
 231     for (i = 0; i < nvqs; i++) {
 232         VirtQueue *vq = virtio_get_queue(s->vdev, i);
 233
 234         virtio_queue_aio_set_host_notifier_handler(vq, s->ctx,
 235                 virtio_blk_data_plane_handle_output);
 236     }
 237     aio_context_release(s->ctx);
 238     return 0;
 239
 240   fail_guest_notifiers:
 241     vblk->dataplane_disabled = true;
 242     s->starting = false;
 243     vblk->dataplane_started = true;
 244     return -ENOSYS;
 245 }
 246
 247 /* Stop notifications for new requests from guest.
 248  *
 249  * Context: BH in IOThread
 250  */
 251 static void virtio_blk_data_plane_stop_bh(void *opaque)
 252 {
 253     VirtIOBlockDataPlane *s = opaque;
 254     unsigned i;
 255
 256     for (i = 0; i < s->conf->num_queues; i++) {
 257         VirtQueue *vq = virtio_get_queue(s->vdev, i);
 258
 259         virtio_queue_aio_set_host_notifier_handler(vq, s->ctx, NULL);
 260     }
 261 }
 262
 263 /* Context: QEMU global mutex held */
 264 void virtio_blk_data_plane_stop(VirtIODevice *vdev)
 265 {
 266     VirtIOBlock *vblk = VIRTIO_BLK(vdev);
 267     VirtIOBlockDataPlane *s = vblk->dataplane;
 268     BusState *qbus = qdev_get_parent_bus(DEVICE(vblk));
 269     VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
 270     unsigned i;
 271     unsigned nvqs = s->conf->num_queues;
 272
 273     if (!vblk->dataplane_started || s->stopping) {
 274         return;
 275     }
 276
 277     /* Better luck next time. */
 278     if (vblk->dataplane_disabled) {
 279         vblk->dataplane_disabled = false;
 280         vblk->dataplane_started = false;
 281         return;
 282     }
 283     s->stopping = true;
 284     trace_virtio_blk_data_plane_stop(s);
 285
 286     aio_context_acquire(s->ctx);
 287     aio_wait_bh_oneshot(s->ctx, virtio_blk_data_plane_stop_bh, s);
 288
 289     /* Drain and try to switch bs back to the QEMU main loop. If other users
 290      * keep the BlockBackend in the iothread, that's ok */
 291     blk_set_aio_context(s->conf->conf.blk, qemu_get_aio_context(), NULL);
 292
 293     aio_context_release(s->ctx);
 294
 295     for (i = 0; i < nvqs; i++) {
 296         virtio_bus_set_host_notifier(VIRTIO_BUS(qbus), i, false);
 297         virtio_bus_cleanup_host_notifier(VIRTIO_BUS(qbus), i);
 298     }
 299
 300     /* Clean up guest notifier (irq) */
 301     k->set_guest_notifiers(qbus->parent, nvqs, false);
 302
 303     vblk->dataplane_started = false;
 304     s->stopping = false;
 305 }