xen-netfront: Update features after registering netdev

[platform/kernel/linux-rpi.git] / kernel / cpu.c

diff --git a/kernel/cpu.c b/kernel/cpu.c
index e41d453..f3f389e 100644 (file)
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -351,6 +351,8 @@ 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 bool cpu_smt_available __read_mostly;
+
 void __init cpu_smt_disable(bool force)
 {
        if (cpu_smt_control == CPU_SMT_FORCE_DISABLED ||
@@ -365,6 +367,30 @@ 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 before non boot CPUs
+ * are brought up.
+ */
+void __init cpu_smt_check_topology_early(void)
+{
+       if (!topology_smt_supported())
+               cpu_smt_control = CPU_SMT_NOT_SUPPORTED;
+}
+
+/*
+ * If SMT was disabled by BIOS, detect it here, after the CPUs have been
+ * brought online. This ensures the smt/l1tf sysfs entries are consistent
+ * with reality. cpu_smt_available is set to true during the bringup of non
+ * boot CPUs when a SMT sibling is detected. Note, this may overwrite
+ * cpu_smt_control's previous setting.
+ */
+void __init cpu_smt_check_topology(void)
+{
+       if (!cpu_smt_available)
+               cpu_smt_control = CPU_SMT_NOT_SUPPORTED;
+}
+
 static int __init smt_cmdline_disable(char *str)
 {
        cpu_smt_disable(str && !strcmp(str, "force"));
@@ -374,10 +400,18 @@ early_param("nosmt", smt_cmdline_disable);
 
 static inline bool cpu_smt_allowed(unsigned int cpu)
 {
-       if (cpu_smt_control == CPU_SMT_ENABLED)
+       if (topology_is_primary_thread(cpu))
                return true;
 
-       if (topology_is_primary_thread(cpu))
+       /*
+        * If the CPU is not a 'primary' thread and the booted_once bit is
+        * set then the processor has SMT support. Store this information
+        * for the late check of SMT support in cpu_smt_check_topology().
+        */
+       if (per_cpu(cpuhp_state, cpu).booted_once)
+               cpu_smt_available = true;
+
+       if (cpu_smt_control == CPU_SMT_ENABLED)
                return true;
 
        /*
@@ -578,15 +612,15 @@ static void cpuhp_thread_fun(unsigned int cpu)
        bool bringup = st->bringup;
        enum cpuhp_state state;
 
+       if (WARN_ON_ONCE(!st->should_run))
+               return;
+
        /*
         * ACQUIRE for the cpuhp_should_run() load of ->should_run. Ensures
         * that if we see ->should_run we also see the rest of the state.
         */
        smp_mb();
 
-       if (WARN_ON_ONCE(!st->should_run))
-               return;
-
        cpuhp_lock_acquire(bringup);
 
        if (st->single) {
@@ -898,7 +932,8 @@ static int cpuhp_down_callbacks(unsigned int cpu, struct cpuhp_cpu_state *st,
                ret = cpuhp_invoke_callback(cpu, st->state, false, NULL, NULL);
                if (ret) {
                        st->target = prev_state;
-                       undo_cpu_down(cpu, st);
+                       if (st->state < prev_state)
+                               undo_cpu_down(cpu, st);
                        break;
                }
        }
@@ -951,7 +986,7 @@ static int __ref _cpu_down(unsigned int cpu, int tasks_frozen,
         * to do the further cleanups.
         */
        ret = cpuhp_down_callbacks(cpu, st, target);
-       if (ret && st->state > CPUHP_TEARDOWN_CPU && st->state < prev_state) {
+       if (ret && st->state == CPUHP_TEARDOWN_CPU && st->state < prev_state) {
                cpuhp_reset_state(st, prev_state);
                __cpuhp_kick_ap(st);
        }
@@ -2127,9 +2162,6 @@ 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);
 }
@@ -2248,6 +2280,8 @@ void __init boot_cpu_init(void)
  */
 void __init boot_cpu_hotplug_init(void)
 {
+#ifdef CONFIG_SMP
        this_cpu_write(cpuhp_state.booted_once, true);
+#endif
        this_cpu_write(cpuhp_state.state, CPUHP_ONLINE);
 }