On Wed, Jan 31, 2018 at 06:27:56PM +0000, Suzuki K Poulose wrote: > Now that we have the flexibility of defining system features based > on individual CPUs, introduce CPU feature type that can be detected > on a local SCOPE and ignores the conflict on late CPUs. This is > applicable for ARM64_HAS_NO_HW_PREFETCH, where it is fine for > the system to have CPUs without hardware prefetch turning up > later. We only suffer a performance penalty, nothing fatal. > > Cc: Will Deacon <[email protected]> > Cc: Dave Martin <[email protected]> > Signed-off-by: Suzuki K Poulose <[email protected]>
Reviewed-by: Dave Martin <[email protected]> > --- > arch/arm64/include/asm/cpufeature.h | 8 ++++++++ > arch/arm64/kernel/cpufeature.c | 2 +- > 2 files changed, 9 insertions(+), 1 deletion(-) > > diff --git a/arch/arm64/include/asm/cpufeature.h > b/arch/arm64/include/asm/cpufeature.h > index cda62b70d338..7bb3fdec827e 100644 > --- a/arch/arm64/include/asm/cpufeature.h > +++ b/arch/arm64/include/asm/cpufeature.h > @@ -214,6 +214,14 @@ extern struct arm64_ftr_reg arm64_ftr_reg_ctrel0; > */ > #define ARM64_CPUCAP_SYSTEM_FEATURE \ > (ARM64_CPUCAP_SCOPE_SYSTEM | ARM64_CPUCAP_PERMITTED_FOR_LATE_CPU) > +/* > + * CPU feature detected at boot time based on feature of one or more CPUs. > + * All possible conflicts for a late CPU are ignored. > + */ > +#define ARM64_CPUCAP_WEAK_LOCAL_CPU_FEATURE \ > + (ARM64_CPUCAP_SCOPE_LOCAL_CPU | \ > + ARM64_CPUCAP_OPTIONAL_FOR_LATE_CPU | \ > + ARM64_CPUCAP_PERMITTED_FOR_LATE_CPU) > > struct arm64_cpu_capabilities { > const char *desc; > diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c > index c710ef28524e..ecc87aa74c64 100644 > --- a/arch/arm64/kernel/cpufeature.c > +++ b/arch/arm64/kernel/cpufeature.c > @@ -956,7 +956,7 @@ static const struct arm64_cpu_capabilities > arm64_features[] = { > { > .desc = "Software prefetching using PRFM", > .capability = ARM64_HAS_NO_HW_PREFETCH, > - .type = ARM64_CPUCAP_SYSTEM_FEATURE, > + .type = ARM64_CPUCAP_WEAK_LOCAL_CPU_FEATURE, > .matches = has_no_hw_prefetch, > }, > #ifdef CONFIG_ARM64_UAO > -- > 2.14.3 > > > _______________________________________________ > linux-arm-kernel mailing list > [email protected] > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
