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