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Subject[PATCH v0 04/12] x86, microcode: Cleanup cpu hotplug notifier callback
Date
From: Borislav Petkov <borislav.petkov@amd.com>

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>
---
arch/x86/kernel/microcode_core.c | 25 ++++++++++++++++---------
1 file 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;
}

--
1.7.11.rc1


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