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Commit 8e1b706b authored by Jiri Kosina's avatar Jiri Kosina Committed by Thomas Gleixner
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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: default avatarJiri Kosina <jkosina@suse.cz>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Tested-by: default avatarJiri Kosina <jkosina@suse.cz>
Reviewed-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: default avatarJosh Poimboeuf <jpoimboe@redhat.com>
Link: https://lkml.kernel.org/r/20180713142323.039715135@linutronix.de
parent 895ae47f

include/linux/cpu.h

+2 −0
Original line number Diff line number Diff line
@@ -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_ */

kernel/cpu.c

+13 −3
Original line number Diff line number Diff line
@@ -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);