qemu

virtio-scsi-dataplane.c (6716B)

---

 /*
  * Virtio SCSI dataplane
  *
  * Copyright Red Hat, Inc. 2014
  *
  * Authors:
  *   Fam Zheng <famz@redhat.com>
  *
  * This work is licensed under the terms of the GNU GPL, version 2 or later.
  * See the COPYING file in the top-level directory.
  *
  */
 
 #include "qemu/osdep.h"
 #include "qapi/error.h"
 #include "hw/virtio/virtio-scsi.h"
 #include "qemu/error-report.h"
 #include "sysemu/block-backend.h"
 #include "hw/scsi/scsi.h"
 #include "scsi/constants.h"
 #include "hw/virtio/virtio-bus.h"
 #include "hw/virtio/virtio-access.h"
 
 /* Context: QEMU global mutex held */
 void virtio_scsi_dataplane_setup(VirtIOSCSI *s, Error **errp)
 {
     VirtIOSCSICommon *vs = VIRTIO_SCSI_COMMON(s);
     VirtIODevice *vdev = VIRTIO_DEVICE(s);
     BusState *qbus = qdev_get_parent_bus(DEVICE(vdev));
     VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
 
     if (vs->conf.iothread) {
         if (!k->set_guest_notifiers || !k->ioeventfd_assign) {
             error_setg(errp,
                        "device is incompatible with iothread "
                        "(transport does not support notifiers)");
             return;
         }
         if (!virtio_device_ioeventfd_enabled(vdev)) {
             error_setg(errp, "ioeventfd is required for iothread");
             return;
         }
         s->ctx = iothread_get_aio_context(vs->conf.iothread);
     } else {
         if (!virtio_device_ioeventfd_enabled(vdev)) {
             return;
         }
         s->ctx = qemu_get_aio_context();
     }
 }
 
 static int virtio_scsi_set_host_notifier(VirtIOSCSI *s, VirtQueue *vq, int n)
 {
     BusState *qbus = BUS(qdev_get_parent_bus(DEVICE(s)));
     int rc;
 
     /* Set up virtqueue notify */
     rc = virtio_bus_set_host_notifier(VIRTIO_BUS(qbus), n, true);
     if (rc != 0) {
         fprintf(stderr, "virtio-scsi: Failed to set host notifier (%d)\n",
                 rc);
         s->dataplane_fenced = true;
         return rc;
     }
 
     return 0;
 }
 
 /* Context: BH in IOThread */
 static void virtio_scsi_dataplane_stop_bh(void *opaque)
 {
     VirtIOSCSI *s = opaque;
     VirtIOSCSICommon *vs = VIRTIO_SCSI_COMMON(s);
     int i;
 
     virtio_queue_aio_detach_host_notifier(vs->ctrl_vq, s->ctx);
     virtio_queue_aio_detach_host_notifier(vs->event_vq, s->ctx);
     for (i = 0; i < vs->conf.num_queues; i++) {
         virtio_queue_aio_detach_host_notifier(vs->cmd_vqs[i], s->ctx);
     }
 }
 
 /* Context: QEMU global mutex held */
 int virtio_scsi_dataplane_start(VirtIODevice *vdev)
 {
     int i;
     int rc;
     int vq_init_count = 0;
     BusState *qbus = qdev_get_parent_bus(DEVICE(vdev));
     VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
     VirtIOSCSICommon *vs = VIRTIO_SCSI_COMMON(vdev);
     VirtIOSCSI *s = VIRTIO_SCSI(vdev);
 
     if (s->dataplane_started ||
         s->dataplane_starting ||
         s->dataplane_fenced) {
         return 0;
     }
 
     s->dataplane_starting = true;
 
     /* Set up guest notifier (irq) */
     rc = k->set_guest_notifiers(qbus->parent, vs->conf.num_queues + 2, true);
     if (rc != 0) {
         error_report("virtio-scsi: Failed to set guest notifiers (%d), "
                      "ensure -accel kvm is set.", rc);
         goto fail_guest_notifiers;
     }
 
     /*
      * Batch all the host notifiers in a single transaction to avoid
      * quadratic time complexity in address_space_update_ioeventfds().
      */
     memory_region_transaction_begin();
 
     rc = virtio_scsi_set_host_notifier(s, vs->ctrl_vq, 0);
     if (rc != 0) {
         goto fail_host_notifiers;
     }
 
     vq_init_count++;
     rc = virtio_scsi_set_host_notifier(s, vs->event_vq, 1);
     if (rc != 0) {
         goto fail_host_notifiers;
     }
 
     vq_init_count++;
 
     for (i = 0; i < vs->conf.num_queues; i++) {
         rc = virtio_scsi_set_host_notifier(s, vs->cmd_vqs[i], i + 2);
         if (rc) {
             goto fail_host_notifiers;
         }
         vq_init_count++;
     }
 
     memory_region_transaction_commit();
 
     /*
      * These fields are visible to the IOThread so we rely on implicit barriers
      * in aio_context_acquire() on the write side and aio_notify_accept() on
      * the read side.
      */
     s->dataplane_starting = false;
     s->dataplane_started = true;
 
     aio_context_acquire(s->ctx);
     virtio_queue_aio_attach_host_notifier(vs->ctrl_vq, s->ctx);
     virtio_queue_aio_attach_host_notifier_no_poll(vs->event_vq, s->ctx);
 
     for (i = 0; i < vs->conf.num_queues; i++) {
         virtio_queue_aio_attach_host_notifier(vs->cmd_vqs[i], s->ctx);
     }
     aio_context_release(s->ctx);
     return 0;
 
 fail_host_notifiers:
     for (i = 0; i < vq_init_count; i++) {
         virtio_bus_set_host_notifier(VIRTIO_BUS(qbus), i, false);
     }
 
     /*
      * The transaction expects the ioeventfds to be open when it
      * commits. Do it now, before the cleanup loop.
      */
     memory_region_transaction_commit();
 
     for (i = 0; i < vq_init_count; i++) {
         virtio_bus_cleanup_host_notifier(VIRTIO_BUS(qbus), i);
     }
     k->set_guest_notifiers(qbus->parent, vs->conf.num_queues + 2, false);
 fail_guest_notifiers:
     s->dataplane_fenced = true;
     s->dataplane_starting = false;
     s->dataplane_started = true;
     return -ENOSYS;
 }
 
 /* Context: QEMU global mutex held */
 void virtio_scsi_dataplane_stop(VirtIODevice *vdev)
 {
     BusState *qbus = qdev_get_parent_bus(DEVICE(vdev));
     VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
     VirtIOSCSICommon *vs = VIRTIO_SCSI_COMMON(vdev);
     VirtIOSCSI *s = VIRTIO_SCSI(vdev);
     int i;
 
     if (!s->dataplane_started || s->dataplane_stopping) {
         return;
     }
 
     /* Better luck next time. */
     if (s->dataplane_fenced) {
         s->dataplane_fenced = false;
         s->dataplane_started = false;
         return;
     }
     s->dataplane_stopping = true;
 
     aio_context_acquire(s->ctx);
     aio_wait_bh_oneshot(s->ctx, virtio_scsi_dataplane_stop_bh, s);
     aio_context_release(s->ctx);
 
     blk_drain_all(); /* ensure there are no in-flight requests */
 
     /*
      * Batch all the host notifiers in a single transaction to avoid
      * quadratic time complexity in address_space_update_ioeventfds().
      */
     memory_region_transaction_begin();
 
     for (i = 0; i < vs->conf.num_queues + 2; i++) {
         virtio_bus_set_host_notifier(VIRTIO_BUS(qbus), i, false);
     }
 
     /*
      * The transaction expects the ioeventfds to be open when it
      * commits. Do it now, before the cleanup loop.
      */
     memory_region_transaction_commit();
 
     for (i = 0; i < vs->conf.num_queues + 2; i++) {
         virtio_bus_cleanup_host_notifier(VIRTIO_BUS(qbus), i);
     }
 
     /* Clean up guest notifier (irq) */
     k->set_guest_notifiers(qbus->parent, vs->conf.num_queues + 2, false);
     s->dataplane_stopping = false;
     s->dataplane_started = false;
 }