Re: [PATCH] virtio-scsi: Change sense buffer size to 252

Paolo Bonzini
2014-03-06T11:55:45Z

Il 06/03/2014 12:22, Hannes Reinecke ha scritto:
> On 03/06/2014 11:09 AM, Paolo Bonzini wrote:
>> Il 06/03/2014 09:47, Fam Zheng ha scritto:
>>> According to SPC-4, section 4.5.2.1, 252 is the limit of sense
>>> data. So
>>> increase the value.
>>>
>>> Signed-off-by: Fam Zheng <famz@redhat.com>
>>> ---
>>> include/linux/virtio_scsi.h | 2 +-
>>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/include/linux/virtio_scsi.h
>>> b/include/linux/virtio_scsi.h
>>> index 4195b97..a437f7f 100644
>>> --- a/include/linux/virtio_scsi.h
>>> +++ b/include/linux/virtio_scsi.h
>>> @@ -28,7 +28,7 @@
>>> #define _LINUX_VIRTIO_SCSI_H
>>>
>>> #define VIRTIO_SCSI_CDB_SIZE 32
>>> -#define VIRTIO_SCSI_SENSE_SIZE 96
>>> +#define VIRTIO_SCSI_SENSE_SIZE 252
>>>
>>> /* SCSI command request, followed by data-out */
>>> struct virtio_scsi_cmd_req {
>>>
>>
>> Hi Fam, how did you test this?
>
> Is there a specific reason _not_ to use the linux default?
> The SCSI stack typically limits the sense code to
> SCSI_SENSE_BUFFERSIZE, so using other values have a
> limited sense.
> Literally :-)

Indeed I don't think this patch makes a difference. Though I asked not
from the SCSI stack perspective, but because right now both virtio-scsi
targets (QEMU and vhost-scsi) are also truncating at 96.

Paolo