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Commit 1b907f46 authored by Will Deacon's avatar Will Deacon
Browse files

arm64: kconfig: move emulation option under kernel features 



Having the instruction emulation submenu underneath "platform selection"
is a great way to hide options we don't want people to use, but somewhat
confusing when you stumble across it there.

Move the menuconfig option underneath "kernel features", where it makes
a bit more sense.

Signed-off-by: default avatarWill Deacon <will.deacon@arm.com>
parent d784e298

arch/arm64/Kconfig

+52 −54
Original line number Diff line number Diff line
@@ -164,60 +164,6 @@ config ARCH_XGENE 
	help

	  This enables support for AppliedMicro X-Gene SOC Family



comment "Processor Features"



menuconfig ARMV8_DEPRECATED

	bool "Emulate deprecated/obsolete ARMv8 instructions"

	depends on COMPAT

	help

	  Legacy software support may require certain instructions

	  that have been deprecated or obsoleted in the architecture.



	  Enable this config to enable selective emulation of these

	  features.



	  If unsure, say Y



if ARMV8_DEPRECATED



config SWP_EMULATION

	bool "Emulate SWP/SWPB instructions"

	help

	  ARMv8 obsoletes the use of A32 SWP/SWPB instructions such that

	  they are always undefined. Say Y here to enable software

	  emulation of these instructions for userspace using LDXR/STXR.



	  In some older versions of glibc [<=2.8] SWP is used during futex

	  trylock() operations with the assumption that the code will not

	  be preempted. This invalid assumption may be more likely to fail

	  with SWP emulation enabled, leading to deadlock of the user

	  application.



	  NOTE: when accessing uncached shared regions, LDXR/STXR rely

	  on an external transaction monitoring block called a global

	  monitor to maintain update atomicity. If your system does not

	  implement a global monitor, this option can cause programs that

	  perform SWP operations to uncached memory to deadlock.



	  If unsure, say Y



config CP15_BARRIER_EMULATION

	bool "Emulate CP15 Barrier instructions"

	help

	  The CP15 barrier instructions - CP15ISB, CP15DSB, and

	  CP15DMB - are deprecated in ARMv8 (and ARMv7). It is

	  strongly recommended to use the ISB, DSB, and DMB

	  instructions instead.



	  Say Y here to enable software emulation of these

	  instructions for AArch32 userspace code. When this option is

	  enabled, CP15 barrier usage is traced which can help

	  identify software that needs updating.



	  If unsure, say Y



endif



endmenu



menu "Bus support"
@@ -417,6 +363,58 @@ config FORCE_MAX_ZONEORDER 
	default "14" if (ARM64_64K_PAGES && TRANSPARENT_HUGEPAGE)

	default "11"



menuconfig ARMV8_DEPRECATED

	bool "Emulate deprecated/obsolete ARMv8 instructions"

	depends on COMPAT

	help

	  Legacy software support may require certain instructions

	  that have been deprecated or obsoleted in the architecture.



	  Enable this config to enable selective emulation of these

	  features.



	  If unsure, say Y



if ARMV8_DEPRECATED



config SWP_EMULATION

	bool "Emulate SWP/SWPB instructions"

	help

	  ARMv8 obsoletes the use of A32 SWP/SWPB instructions such that

	  they are always undefined. Say Y here to enable software

	  emulation of these instructions for userspace using LDXR/STXR.



	  In some older versions of glibc [<=2.8] SWP is used during futex

	  trylock() operations with the assumption that the code will not

	  be preempted. This invalid assumption may be more likely to fail

	  with SWP emulation enabled, leading to deadlock of the user

	  application.



	  NOTE: when accessing uncached shared regions, LDXR/STXR rely

	  on an external transaction monitoring block called a global

	  monitor to maintain update atomicity. If your system does not

	  implement a global monitor, this option can cause programs that

	  perform SWP operations to uncached memory to deadlock.



	  If unsure, say Y



config CP15_BARRIER_EMULATION

	bool "Emulate CP15 Barrier instructions"

	help

	  The CP15 barrier instructions - CP15ISB, CP15DSB, and

	  CP15DMB - are deprecated in ARMv8 (and ARMv7). It is

	  strongly recommended to use the ISB, DSB, and DMB

	  instructions instead.



	  Say Y here to enable software emulation of these

	  instructions for AArch32 userspace code. When this option is

	  enabled, CP15 barrier usage is traced which can help

	  identify software that needs updating.



	  If unsure, say Y



endif



endmenu



menu "Boot options"