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/main-loop.h"
  20 #include "qemu/thread.h"
  21 #include "qemu/error-report.h"
  22 #include "hw/virtio/virtio-access.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     VirtIODevice *vdev;
  35     QEMUBH *bh;                     /* bh for guest notification */
  36     unsigned long *batch_notify_vqs;
  37     bool batch_notifications;
  38
  39     /* Note that these EventNotifiers are assigned by value.  This is
  40      * fine as long as you do not call event_notifier_cleanup on them
  41      * (because you don't own the file descriptor or handle; you just
  42      * use it).
  43      */
  44     IOThread *iothread;
  45     AioContext *ctx;
  46 };
  47
  48 /* Raise an interrupt to signal guest, if necessary */
  49 void virtio_blk_data_plane_notify(VirtIOBlockDataPlane *s, VirtQueue *vq)
  50 {
  51     if (s->batch_notifications) {
  52         set_bit(virtio_get_queue_index(vq), s->batch_notify_vqs);
  53         qemu_bh_schedule(s->bh);
  54     } else {
  55         virtio_notify_irqfd(s->vdev, vq);
  56     }
  57 }
  58
  59 static void notify_guest_bh(void *opaque)
  60 {
  61     VirtIOBlockDataPlane *s = opaque;
  62     unsigned nvqs = s->conf->num_queues;
  63     unsigned long bitmap[BITS_TO_LONGS(nvqs)];
  64     unsigned j;
  65
  66     memcpy(bitmap, s->batch_notify_vqs, sizeof(bitmap));
  67     memset(s->batch_notify_vqs, 0, sizeof(bitmap));
  68
  69     for (j = 0; j < nvqs; j += BITS_PER_LONG) {
  70         unsigned long bits = bitmap[j / BITS_PER_LONG];
  71
  72         while (bits != 0) {
  73             unsigned i = j + ctzl(bits);
  74             VirtQueue *vq = virtio_get_queue(s->vdev, i);
  75
  76             virtio_notify_irqfd(s->vdev, vq);
  77
  78             bits &= bits - 1; /* clear right-most bit */
  79         }
  80     }
  81 }
  82
  83 /* Context: QEMU global mutex held */
  84 bool virtio_blk_data_plane_create(VirtIODevice *vdev, VirtIOBlkConf *conf,
  85                                   VirtIOBlockDataPlane **dataplane,
  86                                   Error **errp)
  87 {
  88     VirtIOBlockDataPlane *s;
  89     BusState *qbus = BUS(qdev_get_parent_bus(DEVICE(vdev)));
  90     VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
  91
  92     *dataplane = NULL;
  93
  94     if (conf->iothread) {
  95         if (!k->set_guest_notifiers || !k->ioeventfd_assign) {
  96             error_setg(errp,
  97                        "device is incompatible with iothread "
  98                        "(transport does not support notifiers)");
  99             return false;
 100         }
 101         if (!virtio_device_ioeventfd_enabled(vdev)) {
 102             error_setg(errp, "ioeventfd is required for iothread");
 103             return false;
 104         }
 105
 106         /* If dataplane is (re-)enabled while the guest is running there could
 107          * be block jobs that can conflict.
 108          */
 109         if (blk_op_is_blocked(conf->conf.blk, BLOCK_OP_TYPE_DATAPLANE, errp)) {
 110             error_prepend(errp, "cannot start virtio-blk dataplane: ");
 111             return false;
 112         }
 113     }
 114     /* Don't try if transport does not support notifiers. */
 115     if (!virtio_device_ioeventfd_enabled(vdev)) {
 116         return false;
 117     }
 118
 119     s = g_new0(VirtIOBlockDataPlane, 1);
 120     s->vdev = vdev;
 121     s->conf = conf;
 122
 123     if (conf->iothread) {
 124         s->iothread = conf->iothread;
 125         object_ref(OBJECT(s->iothread));
 126         s->ctx = iothread_get_aio_context(s->iothread);
 127     } else {
 128         s->ctx = qemu_get_aio_context();
 129     }
 130     s->bh = aio_bh_new(s->ctx, notify_guest_bh, s);
 131     s->batch_notify_vqs = bitmap_new(conf->num_queues);
 132
 133     *dataplane = s;
 134
 135     return true;
 136 }
 137
 138 /* Context: QEMU global mutex held */
 139 void virtio_blk_data_plane_destroy(VirtIOBlockDataPlane *s)
 140 {
 141     VirtIOBlock *vblk;
 142
 143     if (!s) {
 144         return;
 145     }
 146
 147     vblk = VIRTIO_BLK(s->vdev);
 148     assert(!vblk->dataplane_started);
 149     g_free(s->batch_notify_vqs);
 150     qemu_bh_delete(s->bh);
 151     if (s->iothread) {
 152         object_unref(OBJECT(s->iothread));
 153     }
 154     g_free(s);
 155 }
 156
 157 static bool virtio_blk_data_plane_handle_output(VirtIODevice *vdev,
 158                                                 VirtQueue *vq)
 159 {
 160     VirtIOBlock *s = (VirtIOBlock *)vdev;
 161
 162     assert(s->dataplane);
 163     assert(s->dataplane_started);
 164
 165     return virtio_blk_handle_vq(s, vq);
 166 }
 167
 168 /* Context: QEMU global mutex held */
 169 int virtio_blk_data_plane_start(VirtIODevice *vdev)
 170 {
 171     VirtIOBlock *vblk = VIRTIO_BLK(vdev);
 172     VirtIOBlockDataPlane *s = vblk->dataplane;
 173     BusState *qbus = BUS(qdev_get_parent_bus(DEVICE(vblk)));
 174     VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
 175     AioContext *old_context;
 176     unsigned i;
 177     unsigned nvqs = s->conf->num_queues;
 178     Error *local_err = NULL;
 179     int r;
 180
 181     if (vblk->dataplane_started || s->starting) {
 182         return 0;
 183     }
 184
 185     s->starting = true;
 186
 187     if (!virtio_vdev_has_feature(vdev, VIRTIO_RING_F_EVENT_IDX)) {
 188         s->batch_notifications = true;
 189     } else {
 190         s->batch_notifications = false;
 191     }
 192
 193     /* Set up guest notifier (irq) */
 194     r = k->set_guest_notifiers(qbus->parent, nvqs, true);
 195     if (r != 0) {
 196         error_report("virtio-blk failed to set guest notifier (%d), "
 197                      "ensure -accel kvm is set.", r);
 198         goto fail_guest_notifiers;
 199     }
 200
 201     /* Set up virtqueue notify */
 202     for (i = 0; i < nvqs; i++) {
 203         r = virtio_bus_set_host_notifier(VIRTIO_BUS(qbus), i, true);
 204         if (r != 0) {
 205             fprintf(stderr, "virtio-blk failed to set host notifier (%d)\n", r);
 206             while (i--) {
 207                 virtio_bus_set_host_notifier(VIRTIO_BUS(qbus), i, false);
 208                 virtio_bus_cleanup_host_notifier(VIRTIO_BUS(qbus), i);
 209             }
 210             goto fail_guest_notifiers;
 211         }
 212     }
 213
 214     s->starting = false;
 215     vblk->dataplane_started = true;
 216     trace_virtio_blk_data_plane_start(s);
 217
 218     old_context = blk_get_aio_context(s->conf->conf.blk);
 219     aio_context_acquire(old_context);
 220     r = blk_set_aio_context(s->conf->conf.blk, s->ctx, &local_err);
 221     aio_context_release(old_context);
 222     if (r < 0) {
 223         error_report_err(local_err);
 224         goto fail_guest_notifiers;
 225     }
 226
 227     /* Process queued requests before the ones in vring */
 228     virtio_blk_process_queued_requests(vblk, false);
 229
 230     /* Kick right away to begin processing requests already in vring */
 231     for (i = 0; i < nvqs; i++) {
 232         VirtQueue *vq = virtio_get_queue(s->vdev, i);
 233
 234         event_notifier_set(virtio_queue_get_host_notifier(vq));
 235     }
 236
 237     /* Get this show started by hooking up our callbacks */
 238     aio_context_acquire(s->ctx);
 239     for (i = 0; i < nvqs; i++) {
 240         VirtQueue *vq = virtio_get_queue(s->vdev, i);
 241
 242         virtio_queue_aio_set_host_notifier_handler(vq, s->ctx,
 243                 virtio_blk_data_plane_handle_output);
 244     }
 245     aio_context_release(s->ctx);
 246     return 0;
 247
 248   fail_guest_notifiers:
 249     /*
 250      * If we failed to set up the guest notifiers queued requests will be
 251      * processed on the main context.
 252      */
 253     virtio_blk_process_queued_requests(vblk, false);
 254     vblk->dataplane_disabled = true;
 255     s->starting = false;
 256     vblk->dataplane_started = true;
 257     return -ENOSYS;
 258 }
 259
 260 /* Stop notifications for new requests from guest.
 261  *
 262  * Context: BH in IOThread
 263  */
 264 static void virtio_blk_data_plane_stop_bh(void *opaque)
 265 {
 266     VirtIOBlockDataPlane *s = opaque;
 267     unsigned i;
 268
 269     for (i = 0; i < s->conf->num_queues; i++) {
 270         VirtQueue *vq = virtio_get_queue(s->vdev, i);
 271
 272         virtio_queue_aio_set_host_notifier_handler(vq, s->ctx, NULL);
 273     }
 274 }
 275
 276 /* Context: QEMU global mutex held */
 277 void virtio_blk_data_plane_stop(VirtIODevice *vdev)
 278 {
 279     VirtIOBlock *vblk = VIRTIO_BLK(vdev);
 280     VirtIOBlockDataPlane *s = vblk->dataplane;
 281     BusState *qbus = qdev_get_parent_bus(DEVICE(vblk));
 282     VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
 283     unsigned i;
 284     unsigned nvqs = s->conf->num_queues;
 285
 286     if (!vblk->dataplane_started || s->stopping) {
 287         return;
 288     }
 289
 290     /* Better luck next time. */
 291     if (vblk->dataplane_disabled) {
 292         vblk->dataplane_disabled = false;
 293         vblk->dataplane_started = false;
 294         return;
 295     }
 296     s->stopping = true;
 297     trace_virtio_blk_data_plane_stop(s);
 298
 299     aio_context_acquire(s->ctx);
 300     aio_wait_bh_oneshot(s->ctx, virtio_blk_data_plane_stop_bh, s);
 301
 302     /* Drain and try to switch bs back to the QEMU main loop. If other users
 303      * keep the BlockBackend in the iothread, that's ok */
 304     blk_set_aio_context(s->conf->conf.blk, qemu_get_aio_context(), NULL);
 305
 306     aio_context_release(s->ctx);
 307
 308     for (i = 0; i < nvqs; i++) {
 309         virtio_bus_set_host_notifier(VIRTIO_BUS(qbus), i, false);
 310         virtio_bus_cleanup_host_notifier(VIRTIO_BUS(qbus), i);
 311     }
 312
 313     qemu_bh_cancel(s->bh);
 314     notify_guest_bh(s); /* final chance to notify guest */
 315
 316     /* Clean up guest notifier (irq) */
 317     k->set_guest_notifiers(qbus->parent, nvqs, false);
 318
 319     vblk->dataplane_started = false;
 320     s->stopping = false;
 321 }