x86/Kconfig: Select SCHED_SMT if SMP enabled

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 <[email protected]>
Reviewed-by: Ingo Molnar <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Jiri Kosina <[email protected]>
Cc: Tom Lendacky <[email protected]>
Cc: Josh Poimboeuf <[email protected]>
Cc: Andrea Arcangeli <[email protected]>
Cc: David Woodhouse <[email protected]>
Cc: Tim Chen <[email protected]>
Cc: Andi Kleen <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: Casey Schaufler <[email protected]>
Cc: Asit Mallick <[email protected]>
Cc: Arjan van de Ven <[email protected]>
Cc: Jon Masters <[email protected]>
Cc: Waiman Long <[email protected]>
Cc: Greg KH <[email protected]>
Cc: Dave Stewart <[email protected]>
Cc: Kees Cook <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Ben Hutchings <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>

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