arm64: cpufeature: Document the rules of safe value for features (156e0d57) · Commits · 戴 / test

Document the rules for choosing the safe value for different types of features. Cc: Dave Martin <dave.martin@arm.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Will Deacon <will.deacon@arm.com> Cc: Mark Rutland <mark.rutland@arm.com> Reviewed-by:

Catalin Marinas <catalin.marinas@arm.com> Signed-off-by:

Suzuki K Poulose <suzuki.poulose@arm.com> Signed-off-by:

Will Deacon <will.deacon@arm.com>

arch/arm64/include/asm/cpufeature.h

+14 −1

Original line number	Diff line number	Diff line
		@@ -29,7 +29,20 @@
		#include <linux/jump_label.h>
		#include <linux/kernel.h>

		/* CPU feature register tracking */
		/*
		* CPU feature register tracking
		*
		* The safe value of a CPUID feature field is dependent on the implications
		* of the values assigned to it by the architecture. Based on the relationship
		* between the values, the features are classified into 3 types - LOWER_SAFE,
		* HIGHER_SAFE and EXACT.
		*
		* The lowest value of all the CPUs is chosen for LOWER_SAFE and highest
		* for HIGHER_SAFE. It is expected that all CPUs have the same value for
		* a field when EXACT is specified, failing which, the safe value specified
		* in the table is chosen.
		*/

		enum ftr_type {
		FTR_EXACT, /* Use a predefined safe value */
		FTR_LOWER_SAFE, /* Smaller value is safe */

Admin message