hw/scsi/virtio-scsi-dataplane.c

   1 /*
   2  * Virtio SCSI dataplane
   3  *
   4  * Copyright Red Hat, Inc. 2014
   5  *
   6  * Authors:
   7  *   Fam Zheng <famz@redhat.com>
   8  *
   9  * This work is licensed under the terms of the GNU GPL, version 2 or later.
  10  * See the COPYING file in the top-level directory.
  11  *
  12  */
  13
  14 #include "qemu/osdep.h"
  15 #include "qapi/error.h"
  16 #include "hw/virtio/virtio-scsi.h"
  17 #include "qemu/error-report.h"
  18 #include "sysemu/block-backend.h"
  19 #include "hw/scsi/scsi.h"
  20 #include "scsi/constants.h"
  21 #include "hw/virtio/virtio-bus.h"
  22
  23 /* Context: BQL held */
  24 void virtio_scsi_dataplane_setup(VirtIOSCSI *s, Error **errp)
  25 {
  26     VirtIOSCSICommon *vs = VIRTIO_SCSI_COMMON(s);
  27     VirtIODevice *vdev = VIRTIO_DEVICE(s);
  28     BusState *qbus = qdev_get_parent_bus(DEVICE(vdev));
  29     VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
  30
  31     if (vs->conf.iothread) {
  32         if (!k->set_guest_notifiers || !k->ioeventfd_assign) {
  33             error_setg(errp,
  34                        "device is incompatible with iothread "
  35                        "(transport does not support notifiers)");
  36             return;
  37         }
  38         if (!virtio_device_ioeventfd_enabled(vdev)) {
  39             error_setg(errp, "ioeventfd is required for iothread");
  40             return;
  41         }
  42         s->ctx = iothread_get_aio_context(vs->conf.iothread);
  43     } else {
  44         if (!virtio_device_ioeventfd_enabled(vdev)) {
  45             return;
  46         }
  47         s->ctx = qemu_get_aio_context();
  48     }
  49 }
  50
  51 static int virtio_scsi_set_host_notifier(VirtIOSCSI *s, VirtQueue *vq, int n)
  52 {
  53     BusState *qbus = BUS(qdev_get_parent_bus(DEVICE(s)));
  54     int rc;
  55
  56     /* Set up virtqueue notify */
  57     rc = virtio_bus_set_host_notifier(VIRTIO_BUS(qbus), n, true);
  58     if (rc != 0) {
  59         fprintf(stderr, "virtio-scsi: Failed to set host notifier (%d)\n",
  60                 rc);
  61         s->dataplane_fenced = true;
  62         return rc;
  63     }
  64
  65     return 0;
  66 }
  67
  68 /* Context: BH in IOThread */
  69 static void virtio_scsi_dataplane_stop_bh(void *opaque)
  70 {
  71     VirtIOSCSI *s = opaque;
  72     VirtIOSCSICommon *vs = VIRTIO_SCSI_COMMON(s);
  73     EventNotifier *host_notifier;
  74     int i;
  75
  76     virtio_queue_aio_detach_host_notifier(vs->ctrl_vq, s->ctx);
  77     host_notifier = virtio_queue_get_host_notifier(vs->ctrl_vq);
  78
  79     /*
  80      * Test and clear notifier after disabling event, in case poll callback
  81      * didn't have time to run.
  82      */
  83     virtio_queue_host_notifier_read(host_notifier);
  84
  85     virtio_queue_aio_detach_host_notifier(vs->event_vq, s->ctx);
  86     host_notifier = virtio_queue_get_host_notifier(vs->event_vq);
  87     virtio_queue_host_notifier_read(host_notifier);
  88
  89     for (i = 0; i < vs->conf.num_queues; i++) {
  90         virtio_queue_aio_detach_host_notifier(vs->cmd_vqs[i], s->ctx);
  91         host_notifier = virtio_queue_get_host_notifier(vs->cmd_vqs[i]);
  92         virtio_queue_host_notifier_read(host_notifier);
  93     }
  94 }
  95
  96 /* Context: BQL held */
  97 int virtio_scsi_dataplane_start(VirtIODevice *vdev)
  98 {
  99     int i;
 100     int rc;
 101     int vq_init_count = 0;
 102     BusState *qbus = qdev_get_parent_bus(DEVICE(vdev));
 103     VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
 104     VirtIOSCSICommon *vs = VIRTIO_SCSI_COMMON(vdev);
 105     VirtIOSCSI *s = VIRTIO_SCSI(vdev);
 106
 107     if (s->dataplane_started ||
 108         s->dataplane_starting ||
 109         s->dataplane_fenced) {
 110         return 0;
 111     }
 112
 113     s->dataplane_starting = true;
 114
 115     /* Set up guest notifier (irq) */
 116     rc = k->set_guest_notifiers(qbus->parent, vs->conf.num_queues + 2, true);
 117     if (rc != 0) {
 118         error_report("virtio-scsi: Failed to set guest notifiers (%d), "
 119                      "ensure -accel kvm is set.", rc);
 120         goto fail_guest_notifiers;
 121     }
 122
 123     /*
 124      * Batch all the host notifiers in a single transaction to avoid
 125      * quadratic time complexity in address_space_update_ioeventfds().
 126      */
 127     memory_region_transaction_begin();
 128
 129     rc = virtio_scsi_set_host_notifier(s, vs->ctrl_vq, 0);
 130     if (rc != 0) {
 131         goto fail_host_notifiers;
 132     }
 133
 134     vq_init_count++;
 135     rc = virtio_scsi_set_host_notifier(s, vs->event_vq, 1);
 136     if (rc != 0) {
 137         goto fail_host_notifiers;
 138     }
 139
 140     vq_init_count++;
 141
 142     for (i = 0; i < vs->conf.num_queues; i++) {
 143         rc = virtio_scsi_set_host_notifier(s, vs->cmd_vqs[i], i + 2);
 144         if (rc) {
 145             goto fail_host_notifiers;
 146         }
 147         vq_init_count++;
 148     }
 149
 150     memory_region_transaction_commit();
 151
 152     s->dataplane_starting = false;
 153     s->dataplane_started = true;
 154     smp_wmb(); /* paired with aio_notify_accept() */
 155
 156     if (s->bus.drain_count == 0) {
 157         virtio_queue_aio_attach_host_notifier(vs->ctrl_vq, s->ctx);
 158         virtio_queue_aio_attach_host_notifier_no_poll(vs->event_vq, s->ctx);
 159
 160         for (i = 0; i < vs->conf.num_queues; i++) {
 161             virtio_queue_aio_attach_host_notifier(vs->cmd_vqs[i], s->ctx);
 162         }
 163     }
 164     return 0;
 165
 166 fail_host_notifiers:
 167     for (i = 0; i < vq_init_count; i++) {
 168         virtio_bus_set_host_notifier(VIRTIO_BUS(qbus), i, false);
 169     }
 170
 171     /*
 172      * The transaction expects the ioeventfds to be open when it
 173      * commits. Do it now, before the cleanup loop.
 174      */
 175     memory_region_transaction_commit();
 176
 177     for (i = 0; i < vq_init_count; i++) {
 178         virtio_bus_cleanup_host_notifier(VIRTIO_BUS(qbus), i);
 179     }
 180     k->set_guest_notifiers(qbus->parent, vs->conf.num_queues + 2, false);
 181 fail_guest_notifiers:
 182     s->dataplane_fenced = true;
 183     s->dataplane_starting = false;
 184     s->dataplane_started = true;
 185     return -ENOSYS;
 186 }
 187
 188 /* Context: BQL held */
 189 void virtio_scsi_dataplane_stop(VirtIODevice *vdev)
 190 {
 191     BusState *qbus = qdev_get_parent_bus(DEVICE(vdev));
 192     VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
 193     VirtIOSCSICommon *vs = VIRTIO_SCSI_COMMON(vdev);
 194     VirtIOSCSI *s = VIRTIO_SCSI(vdev);
 195     int i;
 196
 197     if (!s->dataplane_started || s->dataplane_stopping) {
 198         return;
 199     }
 200
 201     /* Better luck next time. */
 202     if (s->dataplane_fenced) {
 203         s->dataplane_fenced = false;
 204         s->dataplane_started = false;
 205         return;
 206     }
 207     s->dataplane_stopping = true;
 208
 209     if (s->bus.drain_count == 0) {
 210         aio_wait_bh_oneshot(s->ctx, virtio_scsi_dataplane_stop_bh, s);
 211     }
 212
 213     blk_drain_all(); /* ensure there are no in-flight requests */
 214
 215     /*
 216      * Batch all the host notifiers in a single transaction to avoid
 217      * quadratic time complexity in address_space_update_ioeventfds().
 218      */
 219     memory_region_transaction_begin();
 220
 221     for (i = 0; i < vs->conf.num_queues + 2; i++) {
 222         virtio_bus_set_host_notifier(VIRTIO_BUS(qbus), i, false);
 223     }
 224
 225     /*
 226      * The transaction expects the ioeventfds to be open when it
 227      * commits. Do it now, before the cleanup loop.
 228      */
 229     memory_region_transaction_commit();
 230
 231     for (i = 0; i < vs->conf.num_queues + 2; i++) {
 232         virtio_bus_cleanup_host_notifier(VIRTIO_BUS(qbus), i);
 233     }
 234
 235     /* Clean up guest notifier (irq) */
 236     k->set_guest_notifiers(qbus->parent, vs->conf.num_queues + 2, false);
 237     s->dataplane_stopping = false;
 238     s->dataplane_started = false;
 239 }