From c5ac43ee8c77b1a38d5223bb8a688b2116f1f958 Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Tue, 29 May 2018 17:48:27 +0200 Subject: cpu/hotplug: Provide knobs to control SMT commit 05736e4ac13c08a4a9b1ef2de26dd31a32cbee57 upstream Provide a command line and a sysfs knob to control SMT. The command line options are: 'nosmt': Enumerate secondary threads, but do not online them 'nosmt=force': Ignore secondary threads completely during enumeration via MP table and ACPI/MADT. The sysfs control file has the following states (read/write): 'on': SMT is enabled. Secondary threads can be freely onlined 'off': SMT is disabled. Secondary threads, even if enumerated cannot be onlined 'forceoff': SMT is permanentely disabled. Writes to the control file are rejected. 'notsupported': SMT is not supported by the CPU The command line option 'nosmt' sets the sysfs control to 'off'. This can be changed to 'on' to reenable SMT during runtime. The command line option 'nosmt=force' sets the sysfs control to 'forceoff'. This cannot be changed during runtime. When SMT is 'on' and the control file is changed to 'off' then all online secondary threads are offlined and attempts to online a secondary thread later on are rejected. When SMT is 'off' and the control file is changed to 'on' then secondary threads can be onlined again. The 'off' -> 'on' transition does not automatically online the secondary threads. When the control file is set to 'forceoff', the behaviour is the same as setting it to 'off', but the operation is irreversible and later writes to the control file are rejected. When the control status is 'notsupported' then writes to the control file are rejected. Signed-off-by: Thomas Gleixner Reviewed-by: Konrad Rzeszutek Wilk Acked-by: Ingo Molnar Signed-off-by: Greg Kroah-Hartman --- arch/Kconfig | 3 +++ 1 file changed, 3 insertions(+) (limited to 'arch/Kconfig') diff --git a/arch/Kconfig b/arch/Kconfig index 400b9e1b2f27..4e01862f58e4 100644 --- a/arch/Kconfig +++ b/arch/Kconfig @@ -13,6 +13,9 @@ config KEXEC_CORE config HAVE_IMA_KEXEC bool +config HOTPLUG_SMT + bool + config OPROFILE tristate "OProfile system profiling" depends on PROFILING -- cgit v1.2.3