Re: [Qemu-devel] [PATCH] scsi-bus: fix endianness bug in store_lun()

[Alexey Kardashevskiy <aik@ozlabs.ru>]

On 16/03/13 19:13, Paolo Bonzini wrote:
> Il 16/03/2013 08:16, Alexey Kardashevskiy ha scritto:
>> SCSI protocol is defined as big endian. The SCSI command REPORT_LUNS
>> returns the list of LUNs, 8 bytes each.
>>
>> The store_lun() function is called from scsi_target_emulate_report_luns()
>> to fill the LUNs list which is sent later to a guest a response. However
>> it puts the 2 bytes long big-endian value while it is 8 bytes long.
>
> No, LUNs are composed of four 2-byte big-endian values.

I cannot find it in "SCSI Commands References Manual"
(for example here - 
http://www.seagate.com/staticfiles/support/disc/manuals/Interface%20manuals/100293068c.pdf 
). It just says that it is 8 bytes per
LUN and SCSI itself is big endian. Could you please point me to
the correct spec?

> What bug are you trying to fix?

It is a ppc64 system firmware/bios (aka SLOF) which expects 8 bytes big
endian value and therefore cannot boot from SCSI devices with LUN!=0.
I can fix QEMU or SLOF but not sure which one.


>
> Paolo
>
>> The patch fixes it. Tested on PPC64 platform.
>>
>> Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
>> ---
>>   hw/scsi-bus.c |    6 +++---
>>   1 file changed, 3 insertions(+), 3 deletions(-)
>>
>> diff --git a/hw/scsi-bus.c b/hw/scsi-bus.c
>> index a97f1cd..7059dc2 100644
>> --- a/hw/scsi-bus.c
>> +++ b/hw/scsi-bus.c
>> @@ -310,11 +310,11 @@ struct SCSITargetReq {
>>   static void store_lun(uint8_t *outbuf, int lun)
>>   {
>>       if (lun < 256) {
>> -        outbuf[1] = lun;
>> +        outbuf[7] = lun;
>>           return;
>>       }
>> -    outbuf[1] = (lun & 255);
>> -    outbuf[0] = (lun >> 8) | 0x40;
>> +    outbuf[7] = (lun & 255);
>> +    outbuf[6] = (lun >> 8) | 0x40;
>>   }
>>
>>   static bool scsi_target_emulate_report_luns(SCSITargetReq *r)
>>
>


-- 
Alexey