Re: [Qemu-devel] [RFC PATCH] target-ppc: Register CPU class per family only when needed

["Andreas Färber" <afaerber@suse.de>]

Am 16.03.2015 um 05:58 schrieb Alexey Kardashevskiy:
> On 03/06/2015 12:17 AM, Alexander Graf wrote:
>> On 05.03.15 02:56, Alexey Kardashevskiy wrote:
>>> At the moment when running in KVM mode, QEMU registers "host" class to
>>> match the current CPU PVR value. It also registers another CPU class
>>> with a CPU family name os if we run QEMU on POWER7 machine, "host" and
>>> "POWER7" classes are created, this way we can always use "-cpu POWER7"
>>> on the actual POWER7 machine.
>>>
>>> The existing code uses DeviceClass::desc field of the CPU class as
>>> a source for the class name; it was pointed out that it is wrong to use
>>> user-visible string as a type name.
>>>
>>> This adds a common CPU class name into PowerPCCPUClass struct.
>>> This makes registration of a CPU named after the family conditional -
>>> PowerPCCPUClass::common_cpu_name has to be non-zero. Only POWER7/POWER8
>>> families have this field initialized by now.
>>>
>>> Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
>>
>> LGTM. Andreas, do you agree?
> 
> 
> Ping?

No, I don't agree. Inventing a new class field just to distinguish
POWER7/POWER8 here seems like a weird idea, and the code placement is
not fixed either.

I gathered that you want -cpu POWER7 and -cpu POWER8 to work on POWER8
hardware and -cpu POWER7 on POWER7, for migration purposes, correct?

What exact PVRs have you tested on and why does it not work without
those types despite the PVR masking? To investigate I need a test case.

Is this just a question of the generic family type being abstract and
needing an updated PVR value? Which other fields are actually used?

Regards,
Andreas

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