Re: [PATCH v2] virtio-scsi: Send "REPORTED LUNS CHANGED" sense data upon disk hotplug events.

[Venu Busireddy <venu.busireddy@oracle.com>]

On 2022-09-21 16:33:35 +0200, Paolo Bonzini wrote:
> On Fri, Sep 16, 2022 at 3:44 AM Venu Busireddy
> <venu.busireddy@oracle.com> wrote:
> > diff --git a/hw/scsi/virtio-scsi.c b/hw/scsi/virtio-scsi.c
> > index 41f2a5630173..69194c7ae23c 100644
> > --- a/hw/scsi/virtio-scsi.c
> > +++ b/hw/scsi/virtio-scsi.c
> > @@ -608,7 +608,19 @@ static void virtio_scsi_command_complete(SCSIRequest *r, size_t resid)
> >
> >      req->resp.cmd.response = VIRTIO_SCSI_S_OK;
> >      req->resp.cmd.status = r->status;
> > -    if (req->resp.cmd.status == GOOD) {
> > +    if (req->dev->reported_luns_changed &&
> > +            (req->req.cmd.cdb[0] != INQUIRY) &&
> > +            (req->req.cmd.cdb[0] != REPORT_LUNS) &&
> > +            (req->req.cmd.cdb[0] != REQUEST_SENSE)) {
> > +        req->dev->reported_luns_changed = false;
> > +        req->resp.cmd.resid = 0;
> > +        req->resp.cmd.status_qualifier = 0;
> > +        req->resp.cmd.status = CHECK_CONDITION;
> > +        sense_len = scsi_build_sense(sense, SENSE_CODE(REPORTED_LUNS_CHANGED));
> > +        qemu_iovec_from_buf(&req->resp_iov, sizeof(req->resp.cmd),
> > +                            sense, sense_len);
> > +        req->resp.cmd.sense_len = virtio_tswap32(vdev, sense_len);
> > +    } else if (req->resp.cmd.status == GOOD) {
> >          req->resp.cmd.resid = virtio_tswap32(vdev, resid);
> >      } else {
> >          req->resp.cmd.resid = 0;
> 
> Hi,
> 
> a unit attention sense must be sent _instead_ of executing the command.
> 
> QEMU already has a function scsi_device_set_ua() that handles
> everything; you have to call it, if reported_luns_changed is true,
> from virtio_scsi_handle_cmd_req_prepare() before scsi_req_new().
> 
> It will also skip GET_CONFIGURATION and GET_EVENT_STATUS_NOTIFICATION
> commands which are further special-cased in 4.1.6.1 of the MMC
> specification.

Thanks, Paolo. I will test your suggestion (as soon as I finish what I
am working currently), and get back with either more questions, or with
a v3 post.

Venu

> > @@ -956,6 +968,7 @@ static void virtio_scsi_hotplug(HotplugHandler *hotplug_dev, DeviceState *dev,
> >          virtio_scsi_push_event(s, sd,
> >                                 VIRTIO_SCSI_T_TRANSPORT_RESET,
> >                                 VIRTIO_SCSI_EVT_RESET_RESCAN);
> > +        s->reported_luns_changed = true;
> >          virtio_scsi_release(s);
> >      }
> >  }
> > @@ -973,6 +986,7 @@ static void virtio_scsi_hotunplug(HotplugHandler *hotplug_dev, DeviceState *dev,
> >          virtio_scsi_push_event(s, sd,
> >                                 VIRTIO_SCSI_T_TRANSPORT_RESET,
> >                                 VIRTIO_SCSI_EVT_RESET_REMOVED);
> > +        s->reported_luns_changed = true;
> >          virtio_scsi_release(s);
> >      }
> >
> > diff --git a/include/hw/virtio/virtio-scsi.h b/include/hw/virtio/virtio-scsi.h
> > index a36aad9c8695..efbcf9ba069a 100644
> > --- a/include/hw/virtio/virtio-scsi.h
> > +++ b/include/hw/virtio/virtio-scsi.h
> > @@ -81,6 +81,7 @@ struct VirtIOSCSI {
> >      SCSIBus bus;
> >      int resetting;
> >      bool events_dropped;
> > +    bool reported_luns_changed;
> >
> >      /* Fields for dataplane below */
> >      AioContext *ctx; /* one iothread per virtio-scsi-pci for now */
> >
>