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Subject[PATCH 4.4 208/266] x86/Kconfig: Select SCHED_SMT if SMP enabled
From: Thomas Gleixner <>

commit dbe733642e01dd108f71436aaea7b328cb28fd87 upstream.

CONFIG_SCHED_SMT is enabled by all distros, so there is not a real point to
have it configurable. The runtime overhead in the core scheduler code is
minimal because the actual SMT scheduling parts are conditional on a static

This allows to expose the scheduler's SMT state static key to the
speculation control code. Alternatively the scheduler's static key could be
made always available when CONFIG_SMP is enabled, but that's just adding an
unused static key to every other architecture for nothing.

Signed-off-by: Thomas Gleixner <>
Reviewed-by: Ingo Molnar <>
Cc: Peter Zijlstra <>
Cc: Andy Lutomirski <>
Cc: Linus Torvalds <>
Cc: Jiri Kosina <>
Cc: Tom Lendacky <>
Cc: Josh Poimboeuf <>
Cc: Andrea Arcangeli <>
Cc: David Woodhouse <>
Cc: Tim Chen <>
Cc: Andi Kleen <>
Cc: Dave Hansen <>
Cc: Casey Schaufler <>
Cc: Asit Mallick <>
Cc: Arjan van de Ven <>
Cc: Jon Masters <>
Cc: Waiman Long <>
Cc: Greg KH <>
Cc: Dave Stewart <>
Cc: Kees Cook <>
Signed-off-by: Ben Hutchings <>
Signed-off-by: Greg Kroah-Hartman <>
arch/x86/Kconfig | 8 +-------
1 file changed, 1 insertion(+), 7 deletions(-)

--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -893,13 +893,7 @@ config NR_CPUS
approximately eight kilobytes to the kernel image.

config SCHED_SMT
- bool "SMT (Hyperthreading) scheduler support"
- depends on SMP
- ---help---
- SMT scheduler support improves the CPU scheduler's decision making
- when dealing with Intel Pentium 4 chips with HyperThreading at a
- cost of slightly increased overhead in some places. If unsure say
- N here.
+ def_bool y if SMP

config SCHED_MC
def_bool y

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