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     VirtIODevice *vdev;
  35     QEMUBH *bh;                     /* bh for guest notification */
  36     unsigned long *batch_notify_vqs;
  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     set_bit(virtio_get_queue_index(vq), s->batch_notify_vqs);
  51     qemu_bh_schedule(s->bh);
  52 }
  53
  54 static void notify_guest_bh(void *opaque)
  55 {
  56     VirtIOBlockDataPlane *s = opaque;
  57     unsigned nvqs = s->conf->num_queues;
  58     unsigned long bitmap[BITS_TO_LONGS(nvqs)];
  59     unsigned j;
  60
  61     memcpy(bitmap, s->batch_notify_vqs, sizeof(bitmap));
  62     memset(s->batch_notify_vqs, 0, sizeof(bitmap));
  63
  64     for (j = 0; j < nvqs; j += BITS_PER_LONG) {
  65         unsigned long bits = bitmap[j];
  66
  67         while (bits != 0) {
  68             unsigned i = j + ctzl(bits);
  69             VirtQueue *vq = virtio_get_queue(s->vdev, i);
  70
  71             virtio_notify_irqfd(s->vdev, vq);
  72
  73             bits &= bits - 1; /* clear right-most bit */
  74         }
  75     }
  76 }
  77
  78 /* Context: QEMU global mutex held */
  79 void virtio_blk_data_plane_create(VirtIODevice *vdev, VirtIOBlkConf *conf,
  80                                   VirtIOBlockDataPlane **dataplane,
  81                                   Error **errp)
  82 {
  83     VirtIOBlockDataPlane *s;
  84     BusState *qbus = BUS(qdev_get_parent_bus(DEVICE(vdev)));
  85     VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
  86
  87     *dataplane = NULL;
  88
  89     if (conf->iothread) {
  90         if (!k->set_guest_notifiers || !k->ioeventfd_assign) {
  91             error_setg(errp,
  92                        "device is incompatible with iothread "
  93                        "(transport does not support notifiers)");
  94             return;
  95         }
  96         if (!virtio_device_ioeventfd_enabled(vdev)) {
  97             error_setg(errp, "ioeventfd is required for iothread");
  98             return;
  99         }
 100
 101         /* If dataplane is (re-)enabled while the guest is running there could
 102          * be block jobs that can conflict.
 103          */
 104         if (blk_op_is_blocked(conf->conf.blk, BLOCK_OP_TYPE_DATAPLANE, errp)) {
 105             error_prepend(errp, "cannot start virtio-blk dataplane: ");
 106             return;
 107         }
 108     }
 109     /* Don't try if transport does not support notifiers. */
 110     if (!virtio_device_ioeventfd_enabled(vdev)) {
 111         return;
 112     }
 113
 114     s = g_new0(VirtIOBlockDataPlane, 1);
 115     s->vdev = vdev;
 116     s->conf = conf;
 117
 118     if (conf->iothread) {
 119         s->iothread = conf->iothread;
 120         object_ref(OBJECT(s->iothread));
 121         s->ctx = iothread_get_aio_context(s->iothread);
 122     } else {
 123         s->ctx = qemu_get_aio_context();
 124     }
 125     s->bh = aio_bh_new(s->ctx, notify_guest_bh, s);
 126     s->batch_notify_vqs = bitmap_new(conf->num_queues);
 127
 128     *dataplane = s;
 129 }
 130
 131 /* Context: QEMU global mutex held */
 132 void virtio_blk_data_plane_destroy(VirtIOBlockDataPlane *s)
 133 {
 134     VirtIOBlock *vblk;
 135
 136     if (!s) {
 137         return;
 138     }
 139
 140     vblk = VIRTIO_BLK(s->vdev);
 141     assert(!vblk->dataplane_started);
 142     g_free(s->batch_notify_vqs);
 143     qemu_bh_delete(s->bh);
 144     if (s->iothread) {
 145         object_unref(OBJECT(s->iothread));
 146     }
 147     g_free(s);
 148 }
 149
 150 static bool virtio_blk_data_plane_handle_output(VirtIODevice *vdev,
 151                                                 VirtQueue *vq)
 152 {
 153     VirtIOBlock *s = (VirtIOBlock *)vdev;
 154
 155     assert(s->dataplane);
 156     assert(s->dataplane_started);
 157
 158     return virtio_blk_handle_vq(s, vq);
 159 }
 160
 161 /* Context: QEMU global mutex held */
 162 int virtio_blk_data_plane_start(VirtIODevice *vdev)
 163 {
 164     VirtIOBlock *vblk = VIRTIO_BLK(vdev);
 165     VirtIOBlockDataPlane *s = vblk->dataplane;
 166     BusState *qbus = BUS(qdev_get_parent_bus(DEVICE(vblk)));
 167     VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
 168     unsigned i;
 169     unsigned nvqs = s->conf->num_queues;
 170     int r;
 171
 172     if (vblk->dataplane_started || s->starting) {
 173         return 0;
 174     }
 175
 176     s->starting = true;
 177
 178     /* Set up guest notifier (irq) */
 179     r = k->set_guest_notifiers(qbus->parent, nvqs, true);
 180     if (r != 0) {
 181         fprintf(stderr, "virtio-blk failed to set guest notifier (%d), "
 182                 "ensure -enable-kvm is set\n", r);
 183         goto fail_guest_notifiers;
 184     }
 185
 186     /* Set up virtqueue notify */
 187     for (i = 0; i < nvqs; i++) {
 188         r = virtio_bus_set_host_notifier(VIRTIO_BUS(qbus), i, true);
 189         if (r != 0) {
 190             fprintf(stderr, "virtio-blk failed to set host notifier (%d)\n", r);
 191             while (i--) {
 192                 virtio_bus_set_host_notifier(VIRTIO_BUS(qbus), i, false);
 193             }
 194             goto fail_guest_notifiers;
 195         }
 196     }
 197
 198     s->starting = false;
 199     vblk->dataplane_started = true;
 200     trace_virtio_blk_data_plane_start(s);
 201
 202     blk_set_aio_context(s->conf->conf.blk, s->ctx);
 203
 204     /* Kick right away to begin processing requests already in vring */
 205     for (i = 0; i < nvqs; i++) {
 206         VirtQueue *vq = virtio_get_queue(s->vdev, i);
 207
 208         event_notifier_set(virtio_queue_get_host_notifier(vq));
 209     }
 210
 211     /* Get this show started by hooking up our callbacks */
 212     aio_context_acquire(s->ctx);
 213     for (i = 0; i < nvqs; i++) {
 214         VirtQueue *vq = virtio_get_queue(s->vdev, i);
 215
 216         virtio_queue_aio_set_host_notifier_handler(vq, s->ctx,
 217                 virtio_blk_data_plane_handle_output);
 218     }
 219     aio_context_release(s->ctx);
 220     return 0;
 221
 222   fail_guest_notifiers:
 223     vblk->dataplane_disabled = true;
 224     s->starting = false;
 225     vblk->dataplane_started = true;
 226     return -ENOSYS;
 227 }
 228
 229 /* Context: QEMU global mutex held */
 230 void virtio_blk_data_plane_stop(VirtIODevice *vdev)
 231 {
 232     VirtIOBlock *vblk = VIRTIO_BLK(vdev);
 233     VirtIOBlockDataPlane *s = vblk->dataplane;
 234     BusState *qbus = qdev_get_parent_bus(DEVICE(vblk));
 235     VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
 236     unsigned i;
 237     unsigned nvqs = s->conf->num_queues;
 238
 239     if (!vblk->dataplane_started || s->stopping) {
 240         return;
 241     }
 242
 243     /* Better luck next time. */
 244     if (vblk->dataplane_disabled) {
 245         vblk->dataplane_disabled = false;
 246         vblk->dataplane_started = false;
 247         return;
 248     }
 249     s->stopping = true;
 250     trace_virtio_blk_data_plane_stop(s);
 251
 252     aio_context_acquire(s->ctx);
 253
 254     /* Stop notifications for new requests from guest */
 255     for (i = 0; i < nvqs; i++) {
 256         VirtQueue *vq = virtio_get_queue(s->vdev, i);
 257
 258         virtio_queue_aio_set_host_notifier_handler(vq, s->ctx, NULL);
 259     }
 260
 261     /* Drain and switch bs back to the QEMU main loop */
 262     blk_set_aio_context(s->conf->conf.blk, qemu_get_aio_context());
 263
 264     aio_context_release(s->ctx);
 265
 266     for (i = 0; i < nvqs; i++) {
 267         virtio_bus_set_host_notifier(VIRTIO_BUS(qbus), i, false);
 268     }
 269
 270     /* Clean up guest notifier (irq) */
 271     k->set_guest_notifiers(qbus->parent, nvqs, false);
 272
 273     vblk->dataplane_started = false;
 274     s->stopping = false;
 275 }