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cpu/hotplug: Expose SMT control init function

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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
This commit is contained in:
Jiri Kosina 2018-07-13 16:23:23 +02:00 committed by Thomas Gleixner
parent 895ae47f99
commit 8e1b706b6e
2 changed files with 15 additions and 3 deletions
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2
include/linux/cpu.h
View File

@ -177,8 +177,10 @@ enum cpuhp_smt_control {
#if defined(CONFIG_SMP) && defined(CONFIG_HOTPLUG_SMT)
extern enum cpuhp_smt_control cpu_smt_control;
extern void cpu_smt_disable(bool force);
#else
# define cpu_smt_control (CPU_SMT_ENABLED)
static inline void cpu_smt_disable(bool force) { }
#endif
#endif /* _LINUX_CPU_H_ */

16
kernel/cpu.c
View File

@ -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);