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

[Paolo Bonzini]

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


> @@ -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 */
>