From: Suzuki K Poulose suzuki.poulose@arm.com
[ Upstream commit 5c137714dd8cae464dbd5f028c07af149e6d09fc ]
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 will.deacon@arm.com Reviewed-by: Dave Martin dave.martin@arm.com Signed-off-by: Suzuki K Poulose suzuki.poulose@arm.com Signed-off-by: Will Deacon will.deacon@arm.com Signed-off-by: Ard Biesheuvel ard.biesheuvel@linaro.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/arm64/include/asm/cpufeature.h | 8 ++++++++ arch/arm64/kernel/cpufeature.c | 2 +- 2 files changed, 9 insertions(+), 1 deletion(-)
--- a/arch/arm64/include/asm/cpufeature.h +++ b/arch/arm64/include/asm/cpufeature.h @@ -235,6 +235,14 @@ extern struct arm64_ftr_reg arm64_ftr_re */ #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; --- a/arch/arm64/kernel/cpufeature.c +++ b/arch/arm64/kernel/cpufeature.c @@ -959,7 +959,7 @@ static const struct arm64_cpu_capabiliti { .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