cpu/hotplug: Expose SMT control init function
The L1TF mitigation will gain a commend line parameter which allows to set
a combination of hypervisor mitigation and SMT control.
Expose cpu_smt_disable() so the command line parser can tweak SMT settings.
[ tglx: Split out of larger patch and made it preserve an already existing
force off state ]
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Jiri Kosina <jkosina@suse.cz>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Josh Poimboeuf <jpoimboe@redhat.com>
Link: https://lkml.kernel.org/r/20180713142323.039715135@linutronix.de
diff --git a/kernel/cpu.c b/kernel/cpu.c
index d79e24d..8453e31 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -347,13 +347,23 @@ EXPORT_SYMBOL_GPL(cpu_hotplug_enable);
enum cpuhp_smt_control cpu_smt_control __read_mostly = CPU_SMT_ENABLED;
EXPORT_SYMBOL_GPL(cpu_smt_control);
-static int __init smt_cmdline_disable(char *str)
+void __init cpu_smt_disable(bool force)
{
- cpu_smt_control = CPU_SMT_DISABLED;
- if (str && !strcmp(str, "force")) {
+ if (cpu_smt_control == CPU_SMT_FORCE_DISABLED ||
+ cpu_smt_control == CPU_SMT_NOT_SUPPORTED)
+ return;
+
+ if (force) {
pr_info("SMT: Force disabled\n");
cpu_smt_control = CPU_SMT_FORCE_DISABLED;
+ } else {
+ cpu_smt_control = CPU_SMT_DISABLED;
}
+}
+
+static int __init smt_cmdline_disable(char *str)
+{
+ cpu_smt_disable(str && !strcmp(str, "force"));
return 0;
}
early_param("nosmt", smt_cmdline_disable);
