Re: [Qemu-devel] [RFC PATCH v2 10/10] virtio-scsi: Hook up with dataplane

[Paolo Bonzini <pbonzini@redhat.com>]

Il 06/08/2014 07:35, Fam Zheng ha scritto:
> This enables the virtio-scsi-dataplane code by setting the iothread
> in virtio-scsi device, and makes any function that is called by
> back from dataplane to cooperate with the caller: they need to be
> vring/iothread aware when handling the requests and using scsi devices
> on the bus.
> 
> Signed-off-by: Fam Zheng <famz@redhat.com>
> ---
>  hw/scsi/virtio-scsi.c | 74 ++++++++++++++++++++++++++++++++++++++++++++++++---
>  1 file changed, 71 insertions(+), 3 deletions(-)
> 
> diff --git a/hw/scsi/virtio-scsi.c b/hw/scsi/virtio-scsi.c
> index 9e78e21..1f2a9b6 100644
> --- a/hw/scsi/virtio-scsi.c
> +++ b/hw/scsi/virtio-scsi.c
> @@ -62,6 +62,22 @@ void virtio_scsi_free_req(VirtIOSCSIReq *req)
>      g_free(req);
>  }
>  
> +static void virtio_scsi_aio_acquire(VirtIOSCSICommon *vs)
> +{
> +    if (vs->dataplane_started) {
> +        assert(vs->ctx);
> +        aio_context_acquire(vs->ctx);
> +    }
> +}
> +
> +static void virtio_scsi_aio_release(VirtIOSCSICommon *vs)
> +{
> +    if (vs->dataplane_started) {
> +        assert(vs->ctx);
> +        aio_context_release(vs->ctx);
> +    }
> +}

These are not needed if you do the acquire/release in
virtio_scsi_push_event.

>  static void virtio_scsi_complete_req(VirtIOSCSIReq *req)
>  {
>      VirtIOSCSI *s = req->dev;
> @@ -69,13 +85,19 @@ static void virtio_scsi_complete_req(VirtIOSCSIReq *req)
>      VirtIODevice *vdev = VIRTIO_DEVICE(s);
>  
>      qemu_iovec_from_buf(&req->resp_iov, 0, &req->resp, req->resp_size);
> -    virtqueue_push(vq, &req->elem, req->qsgl.size + req->resp_iov.size);
> +    if (req->vring) {
> +        assert(req->vq == NULL);
> +        virtio_scsi_vring_push_notify(req);
> +    } else {
> +        virtqueue_push(vq, &req->elem, req->qsgl.size + req->resp_iov.size);
> +        virtio_notify(vdev, vq);
> +    }
> +
>      if (req->sreq) {
>          req->sreq->hba_private = NULL;
>          scsi_req_unref(req->sreq);
>      }
>      virtio_scsi_free_req(req);
> -    virtio_notify(vdev, vq);
>  }
>  
>  static void virtio_scsi_bad_req(void)
> @@ -204,10 +226,16 @@ static void *virtio_scsi_load_request(QEMUFile *f, SCSIRequest *sreq)
>  static void virtio_scsi_do_tmf(VirtIOSCSI *s, VirtIOSCSIReq *req)
>  {
>      SCSIDevice *d = virtio_scsi_device_find(s, req->req.tmf.lun);
> +    VirtIOSCSICommon *vs = (VirtIOSCSICommon *)s;
>      SCSIRequest *r, *next;
>      BusChild *kid;
>      int target;
>  
> +    if (vs->dataplane_started && bdrv_get_aio_context(d->conf.bs) != vs->ctx) {
> +        aio_context_acquire(vs->ctx);
> +        bdrv_set_aio_context(d->conf.bs, vs->ctx);
> +        aio_context_release(vs->ctx);
> +    }
>      /* Here VIRTIO_SCSI_S_OK means "FUNCTION COMPLETE".  */
>      req->resp.tmf.response = VIRTIO_SCSI_S_OK;
>  
> @@ -344,8 +372,13 @@ void virtio_scsi_handle_ctrl_req(VirtIOSCSI *s, VirtIOSCSIReq *req)
>  static void virtio_scsi_handle_ctrl(VirtIODevice *vdev, VirtQueue *vq)
>  {
>      VirtIOSCSI *s = (VirtIOSCSI *)vdev;
> +    VirtIOSCSICommon *vs = (VirtIOSCSICommon *)vdev;
>      VirtIOSCSIReq *req;
>  
> +    if (vs->ctx) {
> +        virtio_scsi_dataplane_start(vs);
> +        return;
> +    }
>      while ((req = virtio_scsi_pop_req(s, vq))) {
>          virtio_scsi_handle_ctrl_req(s, req);
>      }
> @@ -439,6 +472,11 @@ void virtio_scsi_handle_cmd_req(VirtIOSCSI *s, VirtIOSCSIReq *req)
>          virtio_scsi_complete_cmd_req(req);
>          return;
>      }
> +    if (vs->dataplane_started && bdrv_get_aio_context(d->conf.bs) != vs->ctx) {
> +        aio_context_acquire(vs->ctx);
> +        bdrv_set_aio_context(d->conf.bs, vs->ctx);
> +        aio_context_release(vs->ctx);
> +    }
>      req->sreq = scsi_req_new(d, req->req.cmd.tag,
>                               virtio_scsi_get_lun(req->req.cmd.lun),
>                               req->req.cdb, req);
> @@ -461,8 +499,13 @@ static void virtio_scsi_handle_cmd(VirtIODevice *vdev, VirtQueue *vq)
>  {
>      /* use non-QOM casts in the data path */
>      VirtIOSCSI *s = (VirtIOSCSI *)vdev;
> +    VirtIOSCSICommon *vs = (VirtIOSCSICommon *)vdev;
>      VirtIOSCSIReq *req;
>  
> +    if (vs->ctx) {
> +        virtio_scsi_dataplane_start(vs);
> +        return;
> +    }

A migration state change notifier (like in virtio-blk-dataplane) is missing.

>      while ((req = virtio_scsi_pop_req(s, vq))) {
>          virtio_scsi_handle_cmd_req(s, req);
>      }
> @@ -513,6 +556,9 @@ static void virtio_scsi_reset(VirtIODevice *vdev)
>      VirtIOSCSI *s = VIRTIO_SCSI(vdev);
>      VirtIOSCSICommon *vs = VIRTIO_SCSI_COMMON(vdev);
>  
> +    if (vs->ctx) {
> +        virtio_scsi_dataplane_stop(vs);
> +    }
>      s->resetting++;
>      qbus_reset_all(&s->bus.qbus);
>      s->resetting--;
> @@ -555,7 +601,11 @@ void virtio_scsi_push_event(VirtIOSCSI *s, SCSIDevice *dev,
>          return;
>      }
>  
> -    req = virtio_scsi_pop_req(s, vs->event_vq);
> +    if (vs->dataplane_started) {
> +        req = virtio_scsi_pop_req_vring(s, vs->event_vring);
> +    } else {
> +        req = virtio_scsi_pop_req(s, vs->event_vq);
> +    }
>      if (!req) {
>          s->events_dropped = true;
>          return;
> @@ -592,7 +642,12 @@ void virtio_scsi_push_event(VirtIOSCSI *s, SCSIDevice *dev,
>  static void virtio_scsi_handle_event(VirtIODevice *vdev, VirtQueue *vq)
>  {
>      VirtIOSCSI *s = VIRTIO_SCSI(vdev);
> +    VirtIOSCSICommon *vs = (VirtIOSCSICommon *)vdev;
>  
> +    if (vs->ctx) {
> +        virtio_scsi_dataplane_start(vs);
> +        return;
> +    }
>      if (s->events_dropped) {
>          virtio_scsi_push_event(s, NULL, VIRTIO_SCSI_T_NO_EVENT, 0);
>      }
> @@ -602,11 +657,14 @@ static void virtio_scsi_change(SCSIBus *bus, SCSIDevice *dev, SCSISense sense)
>  {
>      VirtIOSCSI *s = container_of(bus, VirtIOSCSI, bus);
>      VirtIODevice *vdev = VIRTIO_DEVICE(s);
> +    VirtIOSCSICommon *vs = (VirtIOSCSICommon *)vdev;
>  
>      if (((vdev->guest_features >> VIRTIO_SCSI_F_CHANGE) & 1) &&
>          dev->type != TYPE_ROM) {
> +        virtio_scsi_aio_acquire(vs);
>          virtio_scsi_push_event(s, dev, VIRTIO_SCSI_T_PARAM_CHANGE,
>                                 sense.asc | (sense.ascq << 8));
> +        virtio_scsi_aio_release(vs);
>      }
>  }
>  
> @@ -614,10 +672,13 @@ static void virtio_scsi_hotplug(SCSIBus *bus, SCSIDevice *dev)
>  {
>      VirtIOSCSI *s = container_of(bus, VirtIOSCSI, bus);
>      VirtIODevice *vdev = VIRTIO_DEVICE(s);
> +    VirtIOSCSICommon *vs = (VirtIOSCSICommon *)vdev;
>  
>      if ((vdev->guest_features >> VIRTIO_SCSI_F_HOTPLUG) & 1) {
> +        virtio_scsi_aio_acquire(vs);
>          virtio_scsi_push_event(s, dev, VIRTIO_SCSI_T_TRANSPORT_RESET,
>                                 VIRTIO_SCSI_EVT_RESET_RESCAN);
> +        virtio_scsi_aio_release(vs);
>      }
>  }
>  
> @@ -625,10 +686,13 @@ static void virtio_scsi_hot_unplug(SCSIBus *bus, SCSIDevice *dev)
>  {
>      VirtIOSCSI *s = container_of(bus, VirtIOSCSI, bus);
>      VirtIODevice *vdev = VIRTIO_DEVICE(s);
> +    VirtIOSCSICommon *vs = (VirtIOSCSICommon *)vdev;
>  
>      if ((vdev->guest_features >> VIRTIO_SCSI_F_HOTPLUG) & 1) {
> +        virtio_scsi_aio_acquire(vs);
>          virtio_scsi_push_event(s, dev, VIRTIO_SCSI_T_TRANSPORT_RESET,
>                                 VIRTIO_SCSI_EVT_RESET_REMOVED);
> +        virtio_scsi_aio_release(vs);
>      }
>  }
>  
> @@ -671,6 +735,10 @@ void virtio_scsi_common_realize(DeviceState *dev, Error **errp,
>          s->cmd_vqs[i] = virtio_add_queue(vdev, VIRTIO_SCSI_VQ_SIZE,
>                                           cmd);
>      }
> +
> +    if (s->conf.iothread) {
> +        virtio_scsi_set_iothread(s, s->conf.iothread);
> +    }
>  }
>  
>  static void virtio_scsi_device_realize(DeviceState *dev, Error **errp)
>