From 5c137714dd8cae464dbd5f028c07af149e6d09fc Mon Sep 17 00:00:00 2001 From: Suzuki K Poulose Date: Mon, 26 Mar 2018 15:12:39 +0100 Subject: [PATCH] arm64: capabilities: Introduce weak features based on local CPU 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 Reviewed-by: Dave Martin Signed-off-by: Suzuki K Poulose Signed-off-by: Will Deacon --- 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 c187b926daf9..effb1c038221 100644 --- a/arch/arm64/include/asm/cpufeature.h +++ b/arch/arm64/include/asm/cpufeature.h @@ -239,6 +239,14 @@ 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 d3301359e981..a80ca94080b7 100644 --- a/arch/arm64/kernel/cpufeature.c +++ b/arch/arm64/kernel/cpufeature.c @@ -1010,7 +1010,7 @@ 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 -- 2.11.0