4.18-stable review patch. If anyone has any objections, please let me know.
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From: Jiri Kosina jkosina@suse.cz
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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- include/linux/cpu.h | 2 ++ kernel/cpu.c | 16 +++++++++++++--- 2 files changed, 15 insertions(+), 3 deletions(-)
--- a/include/linux/cpu.h +++ b/include/linux/cpu.h @@ -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_ */ --- 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);