x86, microcode: Cleanup cpu hotplug notifier callback

Mask out CPU_TASKS_FROZEN bit so that all _FROZEN cases can be dropped.
Also, add some more comments as to why CPU_ONLINE falls through to
CPU_DOWN_FAILED (no break), and for the CPU_DEAD case. Realign debug
printks better.

Idea blatantly stolen from a tglx patch:
http://marc.info/?l=linux-kernel&m=134267779513862

Signed-off-by: Borislav Petkov <borislav.petkov@amd.com>
Link: http://lkml.kernel.org/r/1344361461-10076-5-git-send-email-bp@amd64.org
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>

1 files changed, 16 insertions, 9 deletions

diff --git a/arch/x86/kernel/microcode_core.c b/arch/x86/kernel/microcode_core.c
index 706a5c9b8eb2..dcde544e012c 100644
--- a/arch/x86/kernel/microcode_core.c
+++ b/arch/x86/kernel/microcode_core.c
@@ -470,34 +470,41 @@ mc_cpu_callback(struct notifier_block *nb, unsigned long action, void *hcpu)
         struct device *dev;
 
         dev = get_cpu_device(cpu);
-        switch (action) {
+
+        switch (action & ~CPU_TASKS_FROZEN) {
         case CPU_ONLINE:
-        case CPU_ONLINE_FROZEN:
                 microcode_update_cpu(cpu);
-        case CPU_DOWN_FAILED:
-        case CPU_DOWN_FAILED_FROZEN:
                 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;
+
         case CPU_DOWN_PREPARE:
-        case CPU_DOWN_PREPARE_FROZEN:
                 /* Suspend is in progress, only remove the interface */
                 sysfs_remove_group(&dev->kobj, &mc_attr_group);
                 pr_debug("CPU%d removed\n", cpu);
                 break;
 
         /*
+         * 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.
          */
-        case CPU_UP_CANCELED_FROZEN:
-                /* The CPU refused to come up during a system resume */
-                microcode_fini_cpu(cpu);
-                break;
         }
+
+        /* The CPU refused to come up during a system resume */
+        if (action == CPU_UP_CANCELED_FROZEN)
+                microcode_fini_cpu(cpu);
+
         return NOTIFY_OK;
 }