Messages in this thread | | | Subject | Re: [PATCH 2/2] arm64: Use static keys for CPU features | From | Suzuki K Poulose <> | Date | Fri, 26 Aug 2016 10:22:13 +0100 |
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On 25/08/16 18:26, Catalin Marinas wrote: > This patch adds static keys transparently for all the cpu_hwcaps > features by implementing an array of default-false static keys and > enabling them when detected. The cpus_have_cap() check uses the static > keys if the feature being checked is a constant, otherwise the compiler > generates the bitmap test. > > Because of the early call to static_branch_enable() via > check_local_cpu_errata() -> update_cpu_capabilities(), the jump labels > are initialised in cpuinfo_store_boot_cpu(). > > Cc: Will Deacon <will.deacon@arm.com> > Cc: Suzuki K. Poulose <Suzuki.Poulose@arm.com> > Signed-off-by: Catalin Marinas <catalin.marinas@arm.com> > ---
> static inline int __attribute_const__ > diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c > index 62272eac1352..919b2d0d68ae 100644 > --- a/arch/arm64/kernel/cpufeature.c > +++ b/arch/arm64/kernel/cpufeature.c > @@ -46,6 +46,9 @@ unsigned int compat_elf_hwcap2 __read_mostly; > > DECLARE_BITMAP(cpu_hwcaps, ARM64_NCAPS); > > +DEFINE_STATIC_KEY_ARRAY_FALSE(cpu_hwcap_keys, ARM64_NCAPS); > +EXPORT_SYMBOL(cpu_hwcap_keys); > + > #define __ARM64_FTR_BITS(SIGNED, STRICT, TYPE, SHIFT, WIDTH, SAFE_VAL) \ > { \ > .sign = SIGNED, \ > diff --git a/arch/arm64/kernel/cpuinfo.c b/arch/arm64/kernel/cpuinfo.c > index ed1b84fe6925..6a141e399daf 100644 > --- a/arch/arm64/kernel/cpuinfo.c > +++ b/arch/arm64/kernel/cpuinfo.c > @@ -377,6 +377,12 @@ void cpuinfo_store_cpu(void) > void __init cpuinfo_store_boot_cpu(void) > { > struct cpuinfo_arm64 *info = &per_cpu(cpu_data, 0); > + > + /* > + * Initialise the static keys early as they may be enabled by > + * check_local_cpu_errata() -> update_cpu_capabilities(). > + */ > + jump_label_init(); > __cpuinfo_store_cpu(info);
Catalin,
Just a heads up. I have a patch [1] which moves the "check_local_cpu_errata()" around to smp_prepare_boot_cpu(). This patch should still work fine with that case. Only that may be we could move the jump_lable_init() to smp_prepare_boot_cpu(), before we call "update_cpu_errata_work_arounds()" for Boot CPU.
Either way, this will be useful for some of the other feature checks.
Thanks Suzuki
[1] https://lkml.kernel.org/r/1471525832-21209-4-git-send-email-suzuki.poulose@arm.com
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