Re: [Qemu-devel] [PATCH] Chage disk serial length from 20 to 36

[Paolo Bonzini <pbonzini@redhat.com>]

On 30/08/2016 14:08, Markus Armbruster wrote:
> Paolo Bonzini <pbonzini@redhat.com> writes:
> 
>> On 29/08/2016 09:52, ronyweng@synology.com wrote:
>>> From: ronyweng <ronyweng@synology.com>
>>>
>>> Openstack Cinder assigns volume a 36 characters uuid as serial.
>>> Qemu will shrinks the uuid to 20 characters,
>>> missmatch with original uuid.
>>>
>>> Signed-off-by: Rony Weng <ronyweng@synology.com>
>>> ---
>>>  hw/scsi/scsi-disk.c | 4 ++--
>>>  1 file changed, 2 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/hw/scsi/scsi-disk.c b/hw/scsi/scsi-disk.c
>>> index 836a155..0e1bb68 100644
>>> --- a/hw/scsi/scsi-disk.c
>>> +++ b/hw/scsi/scsi-disk.c
>>> @@ -599,8 +599,8 @@ static int scsi_disk_emulate_inquiry(SCSIRequest *req, uint8_t *outbuf)
>>>              }
>>>  
>>>              l = strlen(s->serial);
>>> -            if (l > 20) {
>>> -                l = 20;
>>> +            if (l > 36) {
>>> +                l = 36;
>>>              }
>>>  
>>>              DPRINTF("Inquiry EVPD[Serial number] "
>>>
>>
>> Cc: qemu-stable@nongnu.org
>>
>> Thanks, queued for 2.8 and 2.7.1
>>
>> Paolo
> 
> Pointing to the applicable SCSI spec chapter & verse in the commit
> message would be nice.  As is, 36 looks as arbitrary as 20.

There is no limit in the SCSI spec.  20 was copy-pasted from virtio-blk
which in turn was copy-pasted from ATA.  So 36 is even more arbitrary,
but bumping it up too much might cause issues (e.g. who knows there's no
off-by-one somewhere if I make it 252, so that 256 is the maximum amount
of returned data).

Thanks,

Paolo