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Subject[PATCH 03/18] x86, mce: Add persistent MCE event
Date
From: Borislav Petkov <borislav.petkov@amd.com>

Add the necessary glue to enable the mce_record tracepoint on boot,
turning it into a persistent event. This exports the MCE buffer through
a debugfs per-CPU file which a userspace daemon can read and process the
error data further.

Signed-off-by: Borislav Petkov <borislav.petkov@amd.com>
---
arch/x86/include/asm/mce.h | 8 +++
arch/x86/kernel/cpu/mcheck/mce.c | 89 ++++++++++++++++++++++++++++++++++++++
2 files changed, 97 insertions(+), 0 deletions(-)
diff --git a/arch/x86/include/asm/mce.h b/arch/x86/include/asm/mce.h
index eb16e94..81f5545 100644
--- a/arch/x86/include/asm/mce.h
+++ b/arch/x86/include/asm/mce.h
@@ -115,6 +115,14 @@ struct mce_log {

#ifdef __KERNEL__

+/*
+ * a per-cpu descriptor of the persistent MCE tracepoint
+ */
+struct mce_tp_desc {
+ struct perf_event *event;
+ struct dentry *debugfs_entry;
+};
+
extern struct atomic_notifier_head x86_mce_decoder_chain;

#include <linux/percpu.h>
diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c
index 3385ea2..9589ebf 100644
--- a/arch/x86/kernel/cpu/mcheck/mce.c
+++ b/arch/x86/kernel/cpu/mcheck/mce.c
@@ -96,6 +96,7 @@ static char *mce_helper_argv[2] = { mce_helper, NULL };

static DECLARE_WAIT_QUEUE_HEAD(mce_wait);
static DEFINE_PER_CPU(struct mce, mces_seen);
+static DEFINE_PER_CPU(struct mce_tp_desc, mce_event);
static int cpu_missing;

/*
@@ -2055,6 +2056,91 @@ static void __cpuinit mce_reenable_cpu(void *h)
}
}

+static struct perf_event_attr pattr = {
+ .type = PERF_TYPE_TRACEPOINT,
+ .size = sizeof(pattr),
+ .sample_type = PERF_SAMPLE_RAW,
+ .persistent = 1,
+};
+
+static struct dentry *mce_add_event_debugfs(struct perf_event *event, int cpu)
+{
+ char buf[14];
+
+ sprintf(buf, "mce_record%d", cpu);
+
+ return debugfs_create_file(buf, S_IRUGO | S_IWUSR,
+ mce_get_debugfs_dir(),
+ event, &perf_pers_fops);
+}
+
+#define MCE_BUF_PAGES 4
+
+static int mce_enable_perf_event_on_cpu(int cpu)
+{
+ struct mce_tp_desc *d = &per_cpu(mce_event, cpu);
+ int err = -EINVAL;
+
+ d->event = perf_enable_persistent_event(&pattr, cpu, MCE_BUF_PAGES);
+ if (IS_ERR(d->event)) {
+ printk(KERN_ERR "MCE: Error enabling event on cpu %d\n", cpu);
+ goto ret;
+ }
+
+ d->debugfs_entry = mce_add_event_debugfs(d->event, cpu);
+ if (!d->debugfs_entry) {
+ printk(KERN_ERR "MCE: Error adding event debugfs entry on cpu %d\n", cpu);
+ goto disable;
+ }
+
+ return 0;
+
+disable:
+ perf_disable_persistent_event(d->event, cpu);
+
+ret:
+ return err;
+}
+
+static void mce_disable_perf_event_on_cpu(int cpu)
+{
+ struct mce_tp_desc *d = &per_cpu(mce_event, cpu);
+ debugfs_remove(d->debugfs_entry);
+ perf_disable_persistent_event(d->event, cpu);
+}
+
+static __init int mcheck_init_persistent_event(void)
+{
+ int cpu, err = 0;
+
+ get_online_cpus();
+
+ pattr.config = event_mce_record.event.type;
+ pattr.sample_period = 1;
+ pattr.wakeup_events = 1;
+
+ for_each_online_cpu(cpu)
+ if (mce_enable_perf_event_on_cpu(cpu))
+ goto err_unwind;
+
+ goto unlock;
+
+err_unwind:
+ err = -EINVAL;
+ for (--cpu; cpu >= 0; cpu--)
+ mce_disable_perf_event_on_cpu(cpu);
+
+unlock:
+ put_online_cpus();
+
+ return err;
+}
+
+/*
+ * This has to run after event_trace_init()
+ */
+device_initcall(mcheck_init_persistent_event);
+
/* Get notified when a cpu comes on/off. Be hotplug friendly. */
static int __cpuinit
mce_cpu_callback(struct notifier_block *nfb, unsigned long action, void *hcpu)
@@ -2068,6 +2154,7 @@ mce_cpu_callback(struct notifier_block *nfb, unsigned long action, void *hcpu)
mce_create_device(cpu);
if (threshold_cpu_callback)
threshold_cpu_callback(action, cpu);
+ mce_enable_perf_event_on_cpu(cpu);
break;
case CPU_DEAD:
case CPU_DEAD_FROZEN:
@@ -2077,6 +2164,7 @@ mce_cpu_callback(struct notifier_block *nfb, unsigned long action, void *hcpu)
break;
case CPU_DOWN_PREPARE:
case CPU_DOWN_PREPARE_FROZEN:
+ mce_disable_perf_event_on_cpu(cpu);
del_timer_sync(t);
smp_call_function_single(cpu, mce_disable_cpu, &action, 1);
break;
@@ -2088,6 +2176,7 @@ mce_cpu_callback(struct notifier_block *nfb, unsigned long action, void *hcpu)
add_timer_on(t, cpu);
}
smp_call_function_single(cpu, mce_reenable_cpu, &action, 1);
+ mce_enable_perf_event_on_cpu(cpu);
break;
case CPU_POST_DEAD:
/* intentionally ignoring frozen here */
--
1.7.4.rc2


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