Re: [Qemu-devel] [PATCH 1/2] scsi: Make LUN 0 a simple enclosure

[Hannes Reinecke]

On 08/03/2017 03:32 PM, Daniel P. Berrange wrote:
> On Thu, Aug 03, 2017 at 03:27:00PM +0200, Hannes Reinecke wrote:
>> Instead of having an 'invisible' LUN0 (in case LUN 0 is not connected)
>> this patch maks LUN0 a enclosure service, exposing it to the OS.
>>
>> Signed-off-by: Hannes Reinecke <address@hidden>
>> ---
>>  hw/scsi/scsi-bus.c | 56 
>> +++++++++++++++++++++++++++++++++++++++++++++++++++++-
>>  1 file changed, 55 insertions(+), 1 deletion(-)
>>
>> diff --git a/hw/scsi/scsi-bus.c b/hw/scsi/scsi-bus.c
>> index 23c51de..c89e82d 100644
>> --- a/hw/scsi/scsi-bus.c
>> +++ b/hw/scsi/scsi-bus.c
>> @@ -493,10 +493,11 @@ static bool scsi_target_emulate_inquiry(SCSITargetReq 
>> *r)
>>      if (r->req.lun != 0) {
>>          r->buf[0] = TYPE_NO_LUN;
>>      } else {
>> -        r->buf[0] = TYPE_NOT_PRESENT | TYPE_INACTIVE;
>> +        r->buf[0] = TYPE_ENCLOSURE;
>>          r->buf[2] = 5; /* Version */
>>          r->buf[3] = 2 | 0x10; /* HiSup, response data format */
>>          r->buf[4] = r->len - 5; /* Additional Length = (Len - 1) - 4 */
>> +        r->buf[6] = 0x40; /* Enclosure service */
>>          r->buf[7] = 0x10 | (r->req.bus->info->tcq ? 0x02 : 0); /* Sync, 
>> TCQ.  */
>>          memcpy(&r->buf[8], "QEMU    ", 8);
>>          memcpy(&r->buf[16], "QEMU TARGET     ", 16);
> 
> I would think this needs to be tied into machine type version, otherwise
> when you migrate old to new QEMU, LUN0 is suddenly going to change beneath
> the running guest ?
> 
(I _knew_ this would be coming ...)

It will only change if LUN0 is _not_ assigned, ie if a LUN larger than 0
is the first LUN on that host.
In those cases the system would see an additional LUN, correct.
But as that LUN is trivially not used I don't really see a problem with
that.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                            zSeries & Storage
address@hidden                                 +49 911 74053 688
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