cpu/hotplug: Set CPU_SMT_NOT_SUPPORTED early

commit fee0aede6f4739c87179eca76136f83210953b86 upstream

The CPU_SMT_NOT_SUPPORTED state is set (if the processor does not support
SMT) when the sysfs SMT control file is initialized.

That was fine so far as this was only required to make the output of the
control file correct and to prevent writes in that case.

With the upcoming l1tf command line parameter, this needs to be set up
before the L1TF mitigation selection and command line parsing happens.

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/20180713142323.121795971@linutronix.de
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 23aa3de93920e7997dc88b23b1405cf6b0712d09..ddc2dfeb3d59bbb41f94b43066a858e81a5c8f09 100644 (file)
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -57,6 +57,12 @@ void __init check_bugs(void)
 {
        identify_boot_cpu();
 
+       /*
+        * identify_boot_cpu() initialized SMT support information, let the
+        * core code know.
+        */
+       cpu_smt_check_topology();
+
        if (!IS_ENABLED(CONFIG_SMP)) {
                pr_info("CPU: ");
                print_cpu_info(&boot_cpu_data);

diff --git a/include/linux/cpu.h b/include/linux/cpu.h
index e2a028e4fca98823f33210ca398bf94203d328f0..d059c67e4658f34d8b6311db9e3ebce0059ef9cf 100644 (file)
--- a/include/linux/cpu.h
+++ b/include/linux/cpu.h
@@ -267,9 +267,11 @@ 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);
+extern void cpu_smt_check_topology(void);
 #else
 # define cpu_smt_control               (CPU_SMT_ENABLED)
 static inline void cpu_smt_disable(bool force) { }
+static inline void cpu_smt_check_topology(void) { }
 #endif
 
 #endif /* _LINUX_CPU_H_ */

diff --git a/kernel/cpu.c b/kernel/cpu.c
index e1de463a90f2712daa87dc253f3d905f61cfe87d..8a2ad1587280ea555359c5a92a0065ad5570c76a 100644 (file)
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -374,6 +374,16 @@ void __init cpu_smt_disable(bool force)
        }
 }
 
+/*
+ * The decision whether SMT is supported can only be done after the full
+ * CPU identification. Called from architecture code.
+ */
+void __init cpu_smt_check_topology(void)
+{
+       if (!topology_smt_supported())
+               cpu_smt_control = CPU_SMT_NOT_SUPPORTED;
+}
+
 static int __init smt_cmdline_disable(char *str)
 {
        cpu_smt_disable(str && !strcmp(str, "force"));
@@ -2053,9 +2063,6 @@ static const struct attribute_group cpuhp_smt_attr_group = {
 
 static int __init cpu_smt_state_init(void)
 {
-       if (!topology_smt_supported())
-               cpu_smt_control = CPU_SMT_NOT_SUPPORTED;
-
        return sysfs_create_group(&cpu_subsys.dev_root->kobj,
                                  &cpuhp_smt_attr_group);
 }