4.9-stable review patch. If anyone has any objections, please let me know.
------------------
From: Jiri Kosina <jkos...@suse.cz>
commit 8e1b706b6e819bed215c0db16345568864660393 upstream
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 <jkos...@suse.cz>
Signed-off-by: Thomas Gleixner <t...@linutronix.de>
Tested-by: Jiri Kosina <jkos...@suse.cz>
Reviewed-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
Reviewed-by: Josh Poimboeuf <jpoim...@redhat.com>
Link: https://lkml.kernel.org/r/20180713142323.039715...@linutronix.de
Signed-off-by: David Woodhouse <d...@amazon.co.uk>
Signed-off-by: Greg Kroah-Hartman <gre...@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
@@ -266,8 +266,10 @@ 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
@@ -360,13 +360,23 @@ 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);
