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

["Michael S. Tsirkin" <mst@redhat.com>]

On Wed, Jul 05, 2023 at 09:15:23AM +0200, Stefano Garzarella wrote:
> This reverts commit 8cc5583abe6419e7faaebc9fbd109f34f4c850f2.
> 
> That commit causes several problems in Linux as described in the BZ.
> In particular, after a while, other devices on the bus are no longer
> usable even if those devices are not affected by the hotunplug.
> This may be a problem in Linux, but we have not been able to identify
> it so far. So better to revert this patch until we find a solution.
> 
> Also, Oracle, which initially proposed this patch for a problem with
> Solaris, seems to have already reversed it downstream:
>     https://linux.oracle.com/errata/ELSA-2023-12065.html
> 
> Suggested-by: Thomas Huth <thuth@redhat.com>
> Buglink: https://bugzilla.redhat.com/show_bug.cgi?id=2176702
> Cc: qemu-stable@nongnu.org
> Cc: Mark Kanda <mark.kanda@oracle.com>
> Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>

scsi maintainers, what should be done about this patch?
we don't want a regression in the release ...
revert for now and think what's the right thing to do is
after the release?


> ---
>  include/hw/scsi/scsi.h |  1 -
>  hw/scsi/scsi-bus.c     | 18 ------------------
>  hw/scsi/virtio-scsi.c  |  2 --
>  3 files changed, 21 deletions(-)
> 
> diff --git a/include/hw/scsi/scsi.h b/include/hw/scsi/scsi.h
> index e2bb1a2fbf..7c8adf10b1 100644
> --- a/include/hw/scsi/scsi.h
> +++ b/include/hw/scsi/scsi.h
> @@ -198,7 +198,6 @@ SCSIDevice *scsi_bus_legacy_add_drive(SCSIBus *bus, BlockBackend *blk,
>                                        BlockdevOnError rerror,
>                                        BlockdevOnError werror,
>                                        const char *serial, Error **errp);
> -void scsi_bus_set_ua(SCSIBus *bus, SCSISense sense);
>  void scsi_bus_legacy_handle_cmdline(SCSIBus *bus);
>  
>  SCSIRequest *scsi_req_alloc(const SCSIReqOps *reqops, SCSIDevice *d,
> diff --git a/hw/scsi/scsi-bus.c b/hw/scsi/scsi-bus.c
> index f80f4cb4fc..42a915f8b7 100644
> --- a/hw/scsi/scsi-bus.c
> +++ b/hw/scsi/scsi-bus.c
> @@ -1617,24 +1617,6 @@ static int scsi_ua_precedence(SCSISense sense)
>      return (sense.asc << 8) | sense.ascq;
>  }
>  
> -void scsi_bus_set_ua(SCSIBus *bus, SCSISense sense)
> -{
> -    int prec1, prec2;
> -    if (sense.key != UNIT_ATTENTION) {
> -        return;
> -    }
> -
> -    /*
> -     * Override a pre-existing unit attention condition, except for a more
> -     * important reset condition.
> -     */
> -    prec1 = scsi_ua_precedence(bus->unit_attention);
> -    prec2 = scsi_ua_precedence(sense);
> -    if (prec2 < prec1) {
> -        bus->unit_attention = sense;
> -    }
> -}
> -
>  void scsi_device_set_ua(SCSIDevice *sdev, SCSISense sense)
>  {
>      int prec1, prec2;
> diff --git a/hw/scsi/virtio-scsi.c b/hw/scsi/virtio-scsi.c
> index 45b95ea070..1f56607100 100644
> --- a/hw/scsi/virtio-scsi.c
> +++ b/hw/scsi/virtio-scsi.c
> @@ -1080,7 +1080,6 @@ static void virtio_scsi_hotplug(HotplugHandler *hotplug_dev, DeviceState *dev,
>  
>          virtio_scsi_acquire(s);
>          virtio_scsi_push_event(s, &info);
> -        scsi_bus_set_ua(&s->bus, SENSE_CODE(REPORTED_LUNS_CHANGED));
>          virtio_scsi_release(s);
>      }
>  }
> @@ -1112,7 +1111,6 @@ static void virtio_scsi_hotunplug(HotplugHandler *hotplug_dev, DeviceState *dev,
>      if (virtio_vdev_has_feature(vdev, VIRTIO_SCSI_F_HOTPLUG)) {
>          virtio_scsi_acquire(s);
>          virtio_scsi_push_event(s, &info);
> -        scsi_bus_set_ua(&s->bus, SENSE_CODE(REPORTED_LUNS_CHANGED));
>          virtio_scsi_release(s);
>      }
>  }
> -- 
> 2.41.0