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 #include "hw/virtio/virtio-access.h"
  23
  24 /* Context: QEMU global mutex held */
  25 void virtio_scsi_dataplane_setup(VirtIOSCSI *s, Error **errp)
  26 {
  27     VirtIOSCSICommon *vs = VIRTIO_SCSI_COMMON(s);
  28     VirtIODevice *vdev = VIRTIO_DEVICE(s);
  29     BusState *qbus = qdev_get_parent_bus(DEVICE(vdev));
  30     VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
  31
  32     if (vs->conf.iothread) {
  33         if (!k->set_guest_notifiers || !k->ioeventfd_assign) {
  34             error_setg(errp,
  35                        "device is incompatible with iothread "
  36                        "(transport does not support notifiers)");
  37             return;
  38         }
  39         if (!virtio_device_ioeventfd_enabled(vdev)) {
  40             error_setg(errp, "ioeventfd is required for iothread");
  41             return;
  42         }
  43         s->ctx = iothread_get_aio_context(vs->conf.iothread);
  44     } else {
  45         if (!virtio_device_ioeventfd_enabled(vdev)) {
  46             return;
  47         }
  48         s->ctx = qemu_get_aio_context();
  49     }
  50 }
  51
  52 static int virtio_scsi_set_host_notifier(VirtIOSCSI *s, VirtQueue *vq, int n)
  53 {
  54     BusState *qbus = BUS(qdev_get_parent_bus(DEVICE(s)));
  55     int rc;
  56
  57     /* Set up virtqueue notify */
  58     rc = virtio_bus_set_host_notifier(VIRTIO_BUS(qbus), n, true);
  59     if (rc != 0) {
  60         fprintf(stderr, "virtio-scsi: Failed to set host notifier (%d)\n",
  61                 rc);
  62         s->dataplane_fenced = true;
  63         return rc;
  64     }
  65
  66     return 0;
  67 }
  68
  69 /* Context: BH in IOThread */
  70 static void virtio_scsi_dataplane_stop_bh(void *opaque)
  71 {
  72     VirtIOSCSI *s = opaque;
  73     VirtIOSCSICommon *vs = VIRTIO_SCSI_COMMON(s);
  74     int i;
  75
  76     virtio_queue_aio_detach_host_notifier(vs->ctrl_vq, s->ctx);
  77     virtio_queue_aio_detach_host_notifier(vs->event_vq, s->ctx);
  78     for (i = 0; i < vs->conf.num_queues; i++) {
  79         virtio_queue_aio_detach_host_notifier(vs->cmd_vqs[i], s->ctx);
  80     }
  81 }
  82
  83 /* Context: QEMU global mutex held */
  84 int virtio_scsi_dataplane_start(VirtIODevice *vdev)
  85 {
  86     int i;
  87     int rc;
  88     int vq_init_count = 0;
  89     BusState *qbus = qdev_get_parent_bus(DEVICE(vdev));
  90     VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
  91     VirtIOSCSICommon *vs = VIRTIO_SCSI_COMMON(vdev);
  92     VirtIOSCSI *s = VIRTIO_SCSI(vdev);
  93
  94     if (s->dataplane_started ||
  95         s->dataplane_starting ||
  96         s->dataplane_fenced) {
  97         return 0;
  98     }
  99
 100     s->dataplane_starting = true;
 101
 102     /* Set up guest notifier (irq) */
 103     rc = k->set_guest_notifiers(qbus->parent, vs->conf.num_queues + 2, true);
 104     if (rc != 0) {
 105         error_report("virtio-scsi: Failed to set guest notifiers (%d), "
 106                      "ensure -accel kvm is set.", rc);
 107         goto fail_guest_notifiers;
 108     }
 109
 110     /*
 111      * Batch all the host notifiers in a single transaction to avoid
 112      * quadratic time complexity in address_space_update_ioeventfds().
 113      */
 114     memory_region_transaction_begin();
 115
 116     rc = virtio_scsi_set_host_notifier(s, vs->ctrl_vq, 0);
 117     if (rc != 0) {
 118         goto fail_host_notifiers;
 119     }
 120
 121     vq_init_count++;
 122     rc = virtio_scsi_set_host_notifier(s, vs->event_vq, 1);
 123     if (rc != 0) {
 124         goto fail_host_notifiers;
 125     }
 126
 127     vq_init_count++;
 128
 129     for (i = 0; i < vs->conf.num_queues; i++) {
 130         rc = virtio_scsi_set_host_notifier(s, vs->cmd_vqs[i], i + 2);
 131         if (rc) {
 132             goto fail_host_notifiers;
 133         }
 134         vq_init_count++;
 135     }
 136
 137     memory_region_transaction_commit();
 138
 139     /*
 140      * These fields are visible to the IOThread so we rely on implicit barriers
 141      * in aio_context_acquire() on the write side and aio_notify_accept() on
 142      * the read side.
 143      */
 144     s->dataplane_starting = false;
 145     s->dataplane_started = true;
 146
 147     aio_context_acquire(s->ctx);
 148     virtio_queue_aio_attach_host_notifier(vs->ctrl_vq, s->ctx);
 149     virtio_queue_aio_attach_host_notifier_no_poll(vs->event_vq, s->ctx);
 150
 151     for (i = 0; i < vs->conf.num_queues; i++) {
 152         virtio_queue_aio_attach_host_notifier(vs->cmd_vqs[i], s->ctx);
 153     }
 154     aio_context_release(s->ctx);
 155     return 0;
 156
 157 fail_host_notifiers:
 158     for (i = 0; i < vq_init_count; i++) {
 159         virtio_bus_set_host_notifier(VIRTIO_BUS(qbus), i, false);
 160     }
 161
 162     /*
 163      * The transaction expects the ioeventfds to be open when it
 164      * commits. Do it now, before the cleanup loop.
 165      */
 166     memory_region_transaction_commit();
 167
 168     for (i = 0; i < vq_init_count; i++) {
 169         virtio_bus_cleanup_host_notifier(VIRTIO_BUS(qbus), i);
 170     }
 171     k->set_guest_notifiers(qbus->parent, vs->conf.num_queues + 2, false);
 172 fail_guest_notifiers:
 173     s->dataplane_fenced = true;
 174     s->dataplane_starting = false;
 175     s->dataplane_started = true;
 176     return -ENOSYS;
 177 }
 178
 179 /* Context: QEMU global mutex held */
 180 void virtio_scsi_dataplane_stop(VirtIODevice *vdev)
 181 {
 182     BusState *qbus = qdev_get_parent_bus(DEVICE(vdev));
 183     VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
 184     VirtIOSCSICommon *vs = VIRTIO_SCSI_COMMON(vdev);
 185     VirtIOSCSI *s = VIRTIO_SCSI(vdev);
 186     int i;
 187
 188     if (!s->dataplane_started || s->dataplane_stopping) {
 189         return;
 190     }
 191
 192     /* Better luck next time. */
 193     if (s->dataplane_fenced) {
 194         s->dataplane_fenced = false;
 195         s->dataplane_started = false;
 196         return;
 197     }
 198     s->dataplane_stopping = true;
 199
 200     aio_context_acquire(s->ctx);
 201     aio_wait_bh_oneshot(s->ctx, virtio_scsi_dataplane_stop_bh, s);
 202     aio_context_release(s->ctx);
 203
 204     blk_drain_all(); /* ensure there are no in-flight requests */
 205
 206     /*
 207      * Batch all the host notifiers in a single transaction to avoid
 208      * quadratic time complexity in address_space_update_ioeventfds().
 209      */
 210     memory_region_transaction_begin();
 211
 212     for (i = 0; i < vs->conf.num_queues + 2; i++) {
 213         virtio_bus_set_host_notifier(VIRTIO_BUS(qbus), i, false);
 214     }
 215
 216     /*
 217      * The transaction expects the ioeventfds to be open when it
 218      * commits. Do it now, before the cleanup loop.
 219      */
 220     memory_region_transaction_commit();
 221
 222     for (i = 0; i < vs->conf.num_queues + 2; i++) {
 223         virtio_bus_cleanup_host_notifier(VIRTIO_BUS(qbus), i);
 224     }
 225
 226     /* Clean up guest notifier (irq) */
 227     k->set_guest_notifiers(qbus->parent, vs->conf.num_queues + 2, false);
 228     s->dataplane_stopping = false;
 229     s->dataplane_started = false;
 230 }