Re: [Qemu-ppc] [RFC PATCH] powerpc: add PVR mask support

[Alexander Graf]

On 15.08.2013, at 07:54, Benjamin Herrenschmidt wrote:

> On Thu, 2013-08-15 at 07:21 +0200, Alexander Graf wrote:
>> 
>> Am 15.08.2013 um 05:35 schrieb Alexey Kardashevskiy <address@hidden>:
>> 
>>> IBM POWERPC processors encode PVR as a CPU family in higher 16 bits and
>>> a CPU version in lower 16 bits. Since there is no significant change
>>> in behavior between versions, there is no point to add every single CPU
>>> version in QEMU's CPU list. Also, new CPU versions of already supported
>>> CPU won't break the existing code.
>>> 
>>> This adds a PVR mask support. POWER7, POWER7+ and POWER8 CPUs
>>> definitions converted to use masks.
>> 
>> How does the user select that he wants a v2.3 p7 cpu with this patch?
> 
> It's a tradeoff. We are trading a useless feature (which you describe
> above) for a functional system that doesn't require to have an entry for
> every possible chip revision ever designed and to be designed in the
> future for things to work.

So you're saying it's good to remove a well established feature on 5% of the 
supported CPUs, leave the others inconsistent with the change and then declare 
the whole thing an improvement?

> I know the qemu folks is generally uninterested in making things
> actually work but heh .. :-)

I disagree :).


Alex