Re: [PATCH v2 16/22] arm64/debug: Make use of the system wide safe value

[Suzuki K. Poulose]

On 08/10/15 12:11, Catalin Marinas wrote:
> On Mon, Oct 05, 2015 at 06:02:05PM +0100, Suzuki K. Poulose wrote:
> > @@ -137,13 +138,17 @@ extern struct pmu perf_ops_bp;
> >   /* Determine number of BRP registers available. */
> >   static inline int get_num_brps(void)
> >   {
> > -	return ((read_cpuid(ID_AA64DFR0_EL1) >> 12) & 0xf) + 1;
> > +	return 1 +
> > +		cpuid_feature_extract_field(read_system_reg(SYS_ID_AA64DFR0_EL1),
> > +						ID_AA64DFR0_BRPS_SHIFT);
> >   }
>
> cpuid_feature_extract_field() is fine but we should we bother with
> read_system_reg vs just read_cpuid?
> Similar question for patch 17/22.

Well, we would have already TAINTed the kernel, if these fields are different.
It is just the matter of, whether we want to provide the safer value on a tainted
kernel or not. I am open to suggestions.


Thanks
Suzuki

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