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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index f1c44735a5a63789d6f2768cf84bcfa3b7de227f..603a6e46685231dfb2df5c87a7340965d83797f7 100644 (file)
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -58,6 +58,12 @@ 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 36c8a1aecae43e5f97487d6b47b05c95c4aed9e7..c7712e042aba3a2f209589653cd00d41f6b9d0d1 100644 (file)
--- a/include/linux/cpu.h
+++ b/include/linux/cpu.h
@@ -188,9 +188,11 @@ 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 e41d453e98a598d53e40bf8378edd28ce398e244..877437989a285df8b9c9f74061fcc25ca856908c 100644 (file)
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -365,6 +365,16 @@ 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"));
@@ -2127,9 +2137,6 @@ 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);
 }