Messages in this thread | | | Date | Thu, 10 Oct 2019 18:20:58 +0100 | From | Catalin Marinas <> | Subject | Re: [PATCH 1/4] arm64: add support for the AMU extension v1 |
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Hi Ionela,
On Tue, Sep 17, 2019 at 02:42:25PM +0100, Ionela Voinescu wrote: > +#ifdef CONFIG_ARM64_AMU_EXTN > + > +/* > + * This per cpu variable only signals that the CPU implementation supports the > + * AMU but does not provide information regarding all the events that it > + * supports. > + * When this amu_feat per CPU variable is true, the user of this feature can > + * only rely on the presence of the 4 fixed counters. But this does not > + * guarantee that the counters are enabled or access to these counters is > + * provided by code executed at higher exception levels. > + */ > +DEFINE_PER_CPU(bool, amu_feat) = false; > + > +static void cpu_amu_enable(struct arm64_cpu_capabilities const *cap) > +{ > + if (has_cpuid_feature(cap, SCOPE_LOCAL_CPU)) { > + pr_info("detected CPU%d: Activity Monitors extension\n", > + smp_processor_id()); > + this_cpu_write(amu_feat, true); > + } > +}
Sorry if I missed anything as I just skimmed through this series. I can't see the amu_feat used anywhere in these patches, so on its own it doesn't make much sense.
I also can't see the advantage of allowing mismatched CPU implementations for this feature. What's the intended use-case?
Thanks.
-- Catalin
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