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Commit 0e4a0709 authored by Will Deacon's avatar Will Deacon
Browse files

arm64: kconfig: group the v8.1 features together 



ARMv8 CPUs do not support any of the v8.1 features, so group them
together in Kconfig to make it clear that they're part of 8.1 and not
relevant to older cores.

Signed-off-by: default avatarWill Deacon <will.deacon@arm.com>
parent c739dc83

arch/arm64/Kconfig

+47 −43
Original line number Diff line number Diff line
@@ -481,23 +481,6 @@ config ARM64_VA_BITS 
	default 42 if ARM64_VA_BITS_42

	default 48 if ARM64_VA_BITS_48



config ARM64_HW_AFDBM

	bool "Support for hardware updates of the Access and Dirty page flags"

	default y

	help

	  The ARMv8.1 architecture extensions introduce support for

	  hardware updates of the access and dirty information in page

	  table entries. When enabled in TCR_EL1 (HA and HD bits) on

	  capable processors, accesses to pages with PTE_AF cleared will

	  set this bit instead of raising an access flag fault.

	  Similarly, writes to read-only pages with the DBM bit set will

	  clear the read-only bit (AP[2]) instead of raising a

	  permission fault.



	  Kernels built with this configuration option enabled continue

	  to work on pre-ARMv8.1 hardware and the performance impact is

	  minimal. If unsure, say Y.



config CPU_BIG_ENDIAN

       bool "Build big-endian kernel"

       help
@@ -605,32 +588,6 @@ config FORCE_MAX_ZONEORDER 
	default "14" if (ARM64_64K_PAGES && TRANSPARENT_HUGEPAGE)

	default "11"



config ARM64_PAN

	bool "Enable support for Privileged Access Never (PAN)"

	default y

	help

	 Privileged Access Never (PAN; part of the ARMv8.1 Extensions)

	 prevents the kernel or hypervisor from accessing user-space (EL0)

	 memory directly.



	 Choosing this option will cause any unprotected (not using

	 copy_to_user et al) memory access to fail with a permission fault.



	 The feature is detected at runtime, and will remain as a 'nop'

	 instruction if the cpu does not implement the feature.



config ARM64_LSE_ATOMICS

	bool "ARMv8.1 atomic instructions"

	help

	  As part of the Large System Extensions, ARMv8.1 introduces new

	  atomic instructions that are designed specifically to scale in

	  very large systems.



	  Say Y here to make use of these instructions for the in-kernel

	  atomic routines. This incurs a small overhead on CPUs that do

	  not support these instructions and requires the kernel to be

	  built with binutils >= 2.25.



menuconfig ARMV8_DEPRECATED

	bool "Emulate deprecated/obsolete ARMv8 instructions"

	depends on COMPAT
@@ -698,6 +655,53 @@ config SETEND_EMULATION 
	  If unsure, say Y

endif



menu "ARMv8.1 architectural features"



config ARM64_HW_AFDBM

	bool "Support for hardware updates of the Access and Dirty page flags"

	default y

	help

	  The ARMv8.1 architecture extensions introduce support for

	  hardware updates of the access and dirty information in page

	  table entries. When enabled in TCR_EL1 (HA and HD bits) on

	  capable processors, accesses to pages with PTE_AF cleared will

	  set this bit instead of raising an access flag fault.

	  Similarly, writes to read-only pages with the DBM bit set will

	  clear the read-only bit (AP[2]) instead of raising a

	  permission fault.



	  Kernels built with this configuration option enabled continue

	  to work on pre-ARMv8.1 hardware and the performance impact is

	  minimal. If unsure, say Y.



config ARM64_PAN

	bool "Enable support for Privileged Access Never (PAN)"

	default y

	help

	 Privileged Access Never (PAN; part of the ARMv8.1 Extensions)

	 prevents the kernel or hypervisor from accessing user-space (EL0)

	 memory directly.



	 Choosing this option will cause any unprotected (not using

	 copy_to_user et al) memory access to fail with a permission fault.



	 The feature is detected at runtime, and will remain as a 'nop'

	 instruction if the cpu does not implement the feature.



config ARM64_LSE_ATOMICS

	bool "Atomic instructions"

	help

	  As part of the Large System Extensions, ARMv8.1 introduces new

	  atomic instructions that are designed specifically to scale in

	  very large systems.



	  Say Y here to make use of these instructions for the in-kernel

	  atomic routines. This incurs a small overhead on CPUs that do

	  not support these instructions and requires the kernel to be

	  built with binutils >= 2.25.



endmenu



endmenu



menu "Boot options"