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: QEMU global mutex 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: QEMU global mutex 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     /*
 153      * These fields are visible to the IOThread so we rely on implicit barriers
 154      * in aio_context_acquire() on the write side and aio_notify_accept() on
 155      * the read side.
 156      */
 157     s->dataplane_starting = false;
 158     s->dataplane_started = true;
 159
 160     if (s->bus.drain_count == 0) {
 161         aio_context_acquire(s->ctx);
 162         virtio_queue_aio_attach_host_notifier(vs->ctrl_vq, s->ctx);
 163         virtio_queue_aio_attach_host_notifier_no_poll(vs->event_vq, s->ctx);
 164
 165         for (i = 0; i < vs->conf.num_queues; i++) {
 166             virtio_queue_aio_attach_host_notifier(vs->cmd_vqs[i], s->ctx);
 167         }
 168         aio_context_release(s->ctx);
 169     }
 170     return 0;
 171
 172 fail_host_notifiers:
 173     for (i = 0; i < vq_init_count; i++) {
 174         virtio_bus_set_host_notifier(VIRTIO_BUS(qbus), i, false);
 175     }
 176
 177     /*
 178      * The transaction expects the ioeventfds to be open when it
 179      * commits. Do it now, before the cleanup loop.
 180      */
 181     memory_region_transaction_commit();
 182
 183     for (i = 0; i < vq_init_count; i++) {
 184         virtio_bus_cleanup_host_notifier(VIRTIO_BUS(qbus), i);
 185     }
 186     k->set_guest_notifiers(qbus->parent, vs->conf.num_queues + 2, false);
 187 fail_guest_notifiers:
 188     s->dataplane_fenced = true;
 189     s->dataplane_starting = false;
 190     s->dataplane_started = true;
 191     return -ENOSYS;
 192 }
 193
 194 /* Context: QEMU global mutex held */
 195 void virtio_scsi_dataplane_stop(VirtIODevice *vdev)
 196 {
 197     BusState *qbus = qdev_get_parent_bus(DEVICE(vdev));
 198     VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
 199     VirtIOSCSICommon *vs = VIRTIO_SCSI_COMMON(vdev);
 200     VirtIOSCSI *s = VIRTIO_SCSI(vdev);
 201     int i;
 202
 203     if (!s->dataplane_started || s->dataplane_stopping) {
 204         return;
 205     }
 206
 207     /* Better luck next time. */
 208     if (s->dataplane_fenced) {
 209         s->dataplane_fenced = false;
 210         s->dataplane_started = false;
 211         return;
 212     }
 213     s->dataplane_stopping = true;
 214
 215     if (s->bus.drain_count == 0) {
 216         aio_wait_bh_oneshot(s->ctx, virtio_scsi_dataplane_stop_bh, s);
 217     }
 218
 219     blk_drain_all(); /* ensure there are no in-flight requests */
 220
 221     /*
 222      * Batch all the host notifiers in a single transaction to avoid
 223      * quadratic time complexity in address_space_update_ioeventfds().
 224      */
 225     memory_region_transaction_begin();
 226
 227     for (i = 0; i < vs->conf.num_queues + 2; i++) {
 228         virtio_bus_set_host_notifier(VIRTIO_BUS(qbus), i, false);
 229     }
 230
 231     /*
 232      * The transaction expects the ioeventfds to be open when it
 233      * commits. Do it now, before the cleanup loop.
 234      */
 235     memory_region_transaction_commit();
 236
 237     for (i = 0; i < vs->conf.num_queues + 2; i++) {
 238         virtio_bus_cleanup_host_notifier(VIRTIO_BUS(qbus), i);
 239     }
 240
 241     /* Clean up guest notifier (irq) */
 242     k->set_guest_notifiers(qbus->parent, vs->conf.num_queues + 2, false);
 243     s->dataplane_stopping = false;
 244     s->dataplane_started = false;
 245 }