x86/microcode: Convert to hotplug state machine

Install the callbacks via the state machine. 
CPU_UP_CANCELED_FROZEN() is not preserved: It is only there to free memory in an
error case because it is assumed if the CPU does show up on resume it won't be
seen ever again. As per Borislav:
|IOW, you don't need mc_cpu_dead().

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: rt@linutronix.de
Link: http://lkml.kernel.org/r/20160907164523.46a2xnffha4bv63g@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 17 insertions, 35 deletions

diff --git a/arch/x86/kernel/cpu/microcode/core.c b/arch/x86/kernel/cpu/microcode/core.c
index df04b2d033f6..5ce5155f0695 100644
--- a/arch/x86/kernel/cpu/microcode/core.c
+++ b/arch/x86/kernel/cpu/microcode/core.c
@@ -558,55 +558,36 @@ static struct syscore_ops mc_syscore_ops = {
         .resume                 = mc_bp_resume,
 };
 
-static int
-mc_cpu_callback(struct notifier_block *nb, unsigned long action, void *hcpu)
+static int mc_cpu_online(unsigned int cpu)
 {
-        unsigned int cpu = (unsigned long)hcpu;
         struct device *dev;
 
         dev = get_cpu_device(cpu);
+        microcode_update_cpu(cpu);
+        pr_debug("CPU%d added\n", cpu);
 
-        switch (action & ~CPU_TASKS_FROZEN) {
-        case CPU_ONLINE:
-                microcode_update_cpu(cpu);
-                pr_debug("CPU%d added\n", cpu);
-                /*
-                 * "break" is missing on purpose here because we want to fall
-                 * through in order to create the sysfs group.
-                 */
-
-        case CPU_DOWN_FAILED:
-                if (sysfs_create_group(&dev->kobj, &mc_attr_group))
-                        pr_err("Failed to create group for CPU%d\n", cpu);
-                break;
+        if (sysfs_create_group(&dev->kobj, &mc_attr_group))
+                pr_err("Failed to create group for CPU%d\n", cpu);
+        return 0;
+}
 
-        case CPU_DOWN_PREPARE:
-                /* Suspend is in progress, only remove the interface */
-                sysfs_remove_group(&dev->kobj, &mc_attr_group);
-                pr_debug("CPU%d removed\n", cpu);
-                break;
+static int mc_cpu_down_prep(unsigned int cpu)
+{
+        struct device *dev;
 
+        dev = get_cpu_device(cpu);
+        /* Suspend is in progress, only remove the interface */
+        sysfs_remove_group(&dev->kobj, &mc_attr_group);
+        pr_debug("CPU%d removed\n", cpu);
         /*
-         * case CPU_DEAD:
-         *
          * When a CPU goes offline, don't free up or invalidate the copy of
          * the microcode in kernel memory, so that we can reuse it when the
          * CPU comes back online without unnecessarily requesting the userspace
          * for it again.
          */
-        }
-
-        /* The CPU refused to come up during a system resume */
-        if (action == CPU_UP_CANCELED_FROZEN)
-                microcode_fini_cpu(cpu);
-
-        return NOTIFY_OK;
+        return 0;
 }
 
-static struct notifier_block mc_cpu_notifier = {
-        .notifier_call  = mc_cpu_callback,
-};
-
 static struct attribute *cpu_root_microcode_attrs[] = {
         &dev_attr_reload.attr,
         NULL
@@ -665,7 +646,8 @@ int __init microcode_init(void)
                 goto out_ucode_group;
 
         register_syscore_ops(&mc_syscore_ops);
-        register_hotcpu_notifier(&mc_cpu_notifier);
+        cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN, "x86/microcode:online",
+                                  mc_cpu_online, mc_cpu_down_prep);
 
         pr_info("Microcode Update Driver: v" MICROCODE_VERSION
                 " <tigran@aivazian.fsnet.co.uk>, Peter Oruba\n");