Re: [Qemu-devel] [PATCH v2 2/4] spapr: Use DeviceClass::fw_name for device tree CPU node

["Andreas Färber" <afaerber@suse.de>]

Am 30.08.2013 15:54, schrieb Alexander Graf:
> 
> On 30.08.2013, at 08:05, Alexey Kardashevskiy wrote:
> 
>> On 08/29/2013 03:30 PM, Andreas Färber wrote:
>>> Am 29.08.2013 06:29, schrieb Alexey Kardashevskiy:
>>>> On 08/16/2013 08:35 AM, Andreas Färber wrote:
>>>>> Instead of relying on cpu_model, obtain the device tree node label
>>>>> per CPU. Use DeviceClass::fw_name when available. This implicitly
>>>>> resolves HOST@0 node labels for those CPUs through inheritance.
>>>>>
>>>>> Whenever DeviceClass::fw_name is not available, derive it from the CPU's
>>>>> type name and fill it in for that class with a "PowerPC," prefix for
>>>>> PAPR compliance.
>>>>
>>>>
>>>> I'd rather use the family's @desc instead of CPU class name, would be
>>>> simpler and we would not have nodes like "PowerPC,POWER7-family@0" (this is
>>>> what I get when comment out dc->fw_name for power7 with my PVR patch, just
>>>> to test).
>>>
>>> Negative, desc is a free-text field and may contain spaces, parenthesis,
>>> etc. Each model may set desc differently btw, so given my change request
>>> for the comparison, we might end up with "POWER7 v2.1" on that
>>> particular PVR.
>>
>> These patches are for spapr and spapr-supported CPUs have short nice names
>> in @desc. But ok, may be that's a wrong idea.
>>
>>
>>>> Either way, in what case do you expect that code to work at all? power7,
>>>> 7+, 8 have fw_name field initialized, what else is really supported for
>>>> spapr and requires this workaround?
>>>
>>> 970 comes to mind? Anyway, this was just a more direct way to address
>>> the issues raised by Prerna. If you guys don't see the need to enforce
>>> these naming rules beyond a supported list of POWER CPUs then we can
>>> strip it down further, possibly falling back to a fixed
>>> "PowerPC,UNKNOWN" rather than trying to construct a name.
>>
>>
>> The direct way would be to finish what the series started and assign
>> reasonable fw_name values to every existing family class (970, cell,
>> power6, rs64?).
> 
> I agree :). Then there's no need for magic fw_name generation anymore and we have a very obvious code path, making the code simple.
> 
>> There is very limited set of spapr CPU families, they are all there (except
>> power7+ but I'll have a patch for that too) and new CPU family will require
>> a new class anyway (so we will put fw_name there when we'll be adding the
>> class) OR we implement "compatibility mode" which will use one of existing
>> classes so we get a correct fw_name either way.
> 
> Well, I think it makes sense to always provide a fw_name field, regardless of whether that particular CPU works with sPAPR or not. We could use the same field for ePAPR too for example.

So does ePAPR have the same or similar naming rules? Could you supply us
with verified e500 etc. names so that it's not pure speculation on my part?

Andreas

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