Messages in this thread | | | Date | Fri, 17 Jun 2022 19:24:35 +0100 | From | Catalin Marinas <> | Subject | Re: [PATCH] arm64: errata: add detection for AMEVCNTR01 incrementing incorrectly |
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On Tue, Jun 14, 2022 at 02:42:58PM +0100, Ionela Voinescu wrote: > On Friday 10 Jun 2022 at 17:47:12 (+0100), Catalin Marinas wrote: > > On Tue, Jun 07, 2022 at 01:53:40PM +0100, Ionela Voinescu wrote: > > > diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c > > > index 42ea2bd856c6..b9e4b2bd2c63 100644 > > > --- a/arch/arm64/kernel/cpufeature.c > > > +++ b/arch/arm64/kernel/cpufeature.c > > > @@ -1791,6 +1791,19 @@ int get_cpu_with_amu_feat(void) > > > return cpumask_any(&amu_cpus); > > > } > > > > > > +bool cpu_has_broken_amu_constcnt(void) > > > +{ > > > + /* List of CPUs which have broken AMEVCNTR01 (constant counter) */ > > > + static const struct midr_range cpus[] = { > > > +#ifdef CONFIG_ARM64_ERRATUM_2457168 > > > + MIDR_RANGE(MIDR_CORTEX_A510, 0, 0, 1, 1), > > > +#endif > > > + {}, > > > + }; > > > + > > > + return is_midr_in_range(read_cpuid_id(), cpus); > > > +} > > > > I'd rather not have this in cpufeature.c as it's not really a feature. > > We have some precedent with checking errata in cpufeature.c but IIRC we > > did that only to check whether to enable a feature or not in that file > > (DBM). > > If it's okay with you I can move this to cpu_errata.c:arm64_errata[], but > the type of the capability would have to be > ARM64_CPUCAP_WEAK_LOCAL_CPU_FEATURE. I see there are other workarounds > like this so I hope it's not a problem.
I think this should work. If you want to make a per-CPU decision, instead of checking cpus_have_const_cap(), use this_cpu_has_cap(). It would read the actual CPU regs pretty much like your cpu_has_broken_amu_constcnt() but at least is more unified with the errata framework.
-- Catalin
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