Re: [kvm-unit-tests PATCH] arm/arm64: introduce is_aarch32

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Hi Mark,

On Wed, Nov 16, 2016 at 05:45:44PM +0000, Mark Rutland wrote:
> On Wed, Nov 16, 2016 at 03:38:36PM +0100, Andrew Jones wrote:
> > ARMv7-A isn't exactly the same as ARMv8-A32 (AArch32). This
> > function allows unit tests to make the distinction.
> > 
> > Signed-off-by: Andrew Jones <drjones@xxxxxxxxxx>
> > 
> > ---
> > I'm actually unsure if there's a feature bit or not that I could
> > probe instead. It'd be nice if somebody can confirm. Thanks, drew
> 
> > +/*
> > + * ARMv7-A isn't exactly the same as ARMv8-A32 (AArch32). This
> > + * function allows unit tests to make the distinction.
> > + */
> 
> What do you want this for, specifically?
> 
> Since the CPUID registers were introduced, the architecture goes to
> great lengths to not expose a version, and trying to guess from software
> is a losing battle.
> 
> So I don't think we should try to distinguish ARMv8-A AArch32 from
> ARMv7-A. We should test individual features, or if that's not possible,
> group them in the same bucket.

Perhaps I was too quick to look for a general way to approach the first
place I saw the need, which is

 check_cntr(read_pmccntr());
 if (is_aarch64())
     check_cntr(read_pmccntr64());

Is PMCCNTR the only "weird" difference?

Thanks,
drew

> 
> Thanks,
> Mark.
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