Re: [Qemu-devel] [PULL 00/14] SCSI updates for 2012-07-02

[Hannes Reinecke]

On 07/10/2012 02:52 PM, Anthony Liguori wrote:
> On 07/10/2012 12:57 AM, Hannes Reinecke wrote:
>> On 07/10/2012 01:19 AM, Anthony Liguori wrote:
>>> On 07/09/2012 06:09 PM, Alexander Graf wrote:
>>>>
>>>> On 09.07.2012, at 18:48, Anthony Liguori wrote:
>>>>
>>>>> On 07/02/2012 04:41 AM, Paolo Bonzini wrote:
>>>>>> Anthony,
>>>>>>
>>>>>> The following changes since commit
>>>>>> 71ea2e016131a9fcde6f1ffd3e0e34a64c21f593:
>>>>>>
>>>>>>     bsd-user: fix build (2012-06-28 20:28:36 +0000)
>>>>>
>>>>> Pulled.  Thanks.
>>>>
>>>> Megasas? :)
>>>
>>> So this code is really broken:
>>>
>>>      info.host.type = MFI_INFO_HOST_PCIX;
>>>      info.device.type = MFI_INFO_DEV_SAS3G;
>>>      info.device.port_count = 2;
>>>      info.device.port_addr[0] =
>>> cpu_to_le64(megasas_gen_sas_addr((uint64_t)s));
>>>
>>> This will make migration impossible not to mention the fact that
>>> casting a pointer to a uint64_t is really broken.
>>>
>> Hey, this is _NOT_ an address. It's a simple way of generating a
>> system-wide unique SAS address.
> 
> But it's not stable across migration.  That's the problem.
> 
>> The whole thing is informational anyway, and can only be seen when
>> using the (proprietary) MegaCLI userspace command.
> 
> Nonetheless, it's still guest visible.
> 

Okay, I see your point. I'll be reworking things to not use the
pointer here.

>>> This code needs to be refactored to not do this.  It's quite
>>> pervasive though (there's a half a dozen instances like this).
>>>
>>
>> Okay, so here's the challenge: We need to generate a system-wide
>> unique SAS address, one per SCSI device and one per megasas instance.
>> A simple counter won't work, as we might have several qemu instances
>> running. Which would result in all of them having the same SAS
>> address for the host.
> 
> You could used a hashed uuid.
> 
Right. Will see how that'll work out.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                   zSeries & Storage
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