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Commit efd9e03f authored by Catalin Marinas's avatar Catalin Marinas Committed by Will Deacon
Browse files

arm64: Use static keys for CPU features 



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: default avatarCatalin Marinas <catalin.marinas@arm.com>
Signed-off-by: default avatarWill Deacon <will.deacon@arm.com>
parent ef0da55a

arch/arm64/include/asm/cpufeature.h

+11 −3
Original line number Diff line number Diff line
@@ -9,6 +9,8 @@ 
#ifndef __ASM_CPUFEATURE_H

#define __ASM_CPUFEATURE_H



#include <linux/jump_label.h>



#include <asm/hwcap.h>

#include <asm/sysreg.h>
@@ -110,6 +112,7 @@ struct arm64_cpu_capabilities { 
};



extern DECLARE_BITMAP(cpu_hwcaps, ARM64_NCAPS);

extern struct static_key_false cpu_hwcap_keys[ARM64_NCAPS];



bool this_cpu_has_cap(unsigned int cap);
@@ -122,16 +125,21 @@ static inline bool cpus_have_cap(unsigned int num) 
{

	if (num >= ARM64_NCAPS)

		return false;

	if (__builtin_constant_p(num))

		return static_branch_unlikely(&cpu_hwcap_keys[num]);

	else

		return test_bit(num, cpu_hwcaps);

}



static inline void cpus_set_cap(unsigned int num)

{

	if (num >= ARM64_NCAPS)

	if (num >= ARM64_NCAPS) {

		pr_warn("Attempt to set an illegal CPU capability (%d >= %d)\n",

			num, ARM64_NCAPS);

	else

	} else {

		__set_bit(num, cpu_hwcaps);

		static_branch_enable(&cpu_hwcap_keys[num]);

	}

}



static inline int __attribute_const__

arch/arm64/kernel/cpufeature.c

+3 −0
Original line number Diff line number Diff line
@@ -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,				\

arch/arm64/kernel/smp.c

+5 −0
Original line number Diff line number Diff line
@@ -437,6 +437,11 @@ void __init smp_cpus_done(unsigned int max_cpus) 
void __init smp_prepare_boot_cpu(void)

{

	set_my_cpu_offset(per_cpu_offset(smp_processor_id()));

	/*

	 * Initialise the static keys early as they may be enabled by the

	 * cpufeature code.

	 */

	jump_label_init();

	cpuinfo_store_boot_cpu();

	save_boot_cpu_run_el();

}