From: Thomas Gleixner tglx@linutronix.de
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 key.
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 tglx@linutronix.de Reviewed-by: Ingo Molnar mingo@kernel.org Cc: Peter Zijlstra peterz@infradead.org Cc: Andy Lutomirski luto@kernel.org Cc: Linus Torvalds torvalds@linux-foundation.org Cc: Jiri Kosina jkosina@suse.cz Cc: Tom Lendacky thomas.lendacky@amd.com Cc: Josh Poimboeuf jpoimboe@redhat.com Cc: Andrea Arcangeli aarcange@redhat.com Cc: David Woodhouse dwmw@amazon.co.uk Cc: Tim Chen tim.c.chen@linux.intel.com Cc: Andi Kleen ak@linux.intel.com Cc: Dave Hansen dave.hansen@intel.com Cc: Casey Schaufler casey.schaufler@intel.com Cc: Asit Mallick asit.k.mallick@intel.com Cc: Arjan van de Ven arjan@linux.intel.com Cc: Jon Masters jcm@redhat.com Cc: Waiman Long longman9394@gmail.com Cc: Greg KH gregkh@linuxfoundation.org Cc: Dave Stewart david.c.stewart@intel.com Cc: Kees Cook keescook@chromium.org Link: https://lkml.kernel.org/r/20181125185004.337452245@linutronix.de Signed-off-by: Ben Hutchings ben@decadent.org.uk Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- 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