[PATCH] x86-64: Allow to run a program when a machine check event is detected

When a machine check event is detected (including a AMD RevF threshold
overflow event) allow to run a "trigger" program. This allows user space
to react to such events sooner.

The trigger is configured using a new trigger entry in the
machinecheck sysfs interface. It is currently shared between
all CPUs.

I also fixed the AMD threshold handler to run the machine
check polling code immediately to actually log any events
that might have caused the threshold interrupt.

Also added some documentation for the mce sysfs interface.

Signed-off-by: Andi Kleen <ak@suse.de>

2 files changed, 58 insertions, 12 deletions

diff --git a/arch/x86_64/kernel/mce.c b/arch/x86_64/kernel/mce.c
index bdb54a2..8011a8e 100644
--- a/arch/x86_64/kernel/mce.c
+++ b/arch/x86_64/kernel/mce.c
@@ -19,6 +19,7 @@
 #include <linux/cpu.h>
 #include <linux/percpu.h>
 #include <linux/ctype.h>
+#include <linux/kmod.h>
 #include <asm/processor.h> 
 #include <asm/msr.h>
 #include <asm/mce.h>
@@ -42,6 +43,10 @@ static unsigned long console_logged;
 static int notify_user;
 static int rip_msr;
 static int mce_bootlog = 1;
+static atomic_t mce_events;
+
+static char trigger[128];
+static char *trigger_argv[2] = { trigger, NULL };
 
 /*
  * Lockless MCE logging infrastructure.
@@ -57,6 +62,7 @@ struct mce_log mcelog = {
 void mce_log(struct mce *mce)
 {
 	unsigned next, entry;
+	atomic_inc(&mce_events);
 	mce->finished = 0;
 	wmb();
 	for (;;) {
@@ -161,6 +167,17 @@ static inline void mce_get_rip(struct mce *m, struct pt_regs *regs)
 	}
 }
 
+static void do_mce_trigger(void)
+{
+	static atomic_t mce_logged;
+	int events = atomic_read(&mce_events);
+	if (events != atomic_read(&mce_logged) && trigger[0]) {
+		/* Small race window, but should be harmless.  */
+		atomic_set(&mce_logged, events);
+		call_usermodehelper(trigger, trigger_argv, NULL, -1);
+	}
+}
+
 /* 
  * The actual machine check handler
  */
@@ -234,8 +251,12 @@ void do_machine_check(struct pt_regs * regs, long error_code)
 	}
 
 	/* Never do anything final in the polling timer */
-	if (!regs)
+	if (!regs) {
+		/* Normal interrupt context here. Call trigger for any new
+		   events. */
+		do_mce_trigger();
 		goto out;
+	}
 
 	/* If we didn't find an uncorrectable error, pick
 	   the last one (shouldn't happen, just being safe). */
@@ -606,17 +627,42 @@ DEFINE_PER_CPU(struct sys_device, device_mce);
 	}									   \
 	static SYSDEV_ATTR(name, 0644, show_ ## name, set_ ## name);
 
+/* TBD should generate these dynamically based on number of available banks */
 ACCESSOR(bank0ctl,bank[0],mce_restart())
 ACCESSOR(bank1ctl,bank[1],mce_restart())
 ACCESSOR(bank2ctl,bank[2],mce_restart())
 ACCESSOR(bank3ctl,bank[3],mce_restart())
 ACCESSOR(bank4ctl,bank[4],mce_restart())
 ACCESSOR(bank5ctl,bank[5],mce_restart())
-static struct sysdev_attribute * bank_attributes[NR_BANKS] = {
-	&attr_bank0ctl, &attr_bank1ctl, &attr_bank2ctl,
-	&attr_bank3ctl, &attr_bank4ctl, &attr_bank5ctl};
+
+static ssize_t show_trigger(struct sys_device *s, char *buf)
+{
+	strcpy(buf, trigger);
+	strcat(buf, "\n");
+	return strlen(trigger) + 1;
+}
+
+static ssize_t set_trigger(struct sys_device *s,const char *buf,size_t siz)
+{
+	char *p;
+	int len;
+	strncpy(trigger, buf, sizeof(trigger));
+	trigger[sizeof(trigger)-1] = 0;
+	len = strlen(trigger);
+	p = strchr(trigger, '\n');
+	if (*p) *p = 0;
+	return len;
+}
+
+static SYSDEV_ATTR(trigger, 0644, show_trigger, set_trigger);
 ACCESSOR(tolerant,tolerant,)
 ACCESSOR(check_interval,check_interval,mce_restart())
+static struct sysdev_attribute *mce_attributes[] = {
+	&attr_bank0ctl, &attr_bank1ctl, &attr_bank2ctl,
+	&attr_bank3ctl, &attr_bank4ctl, &attr_bank5ctl,
+	&attr_tolerant, &attr_check_interval, &attr_trigger,
+	NULL
+};
 
 /* Per cpu sysdev init.  All of the cpus still share the same ctl bank */
 static __cpuinit int mce_create_device(unsigned int cpu)
@@ -632,11 +678,9 @@ static __cpuinit int mce_create_device(unsigned int cpu)
 	err = sysdev_register(&per_cpu(device_mce,cpu));
 
 	if (!err) {
-		for (i = 0; i < banks; i++)
+		for (i = 0; mce_attributes[i]; i++)
 			sysdev_create_file(&per_cpu(device_mce,cpu),
-				bank_attributes[i]);
-		sysdev_create_file(&per_cpu(device_mce,cpu), &attr_tolerant);
-		sysdev_create_file(&per_cpu(device_mce,cpu), &attr_check_interval);
+				mce_attributes[i]);
 	}
 	return err;
 }
@@ -645,11 +689,9 @@ static void mce_remove_device(unsigned int cpu)
 {
 	int i;
 
-	for (i = 0; i < banks; i++)
+	for (i = 0; mce_attributes[i]; i++)
 		sysdev_remove_file(&per_cpu(device_mce,cpu),
-			bank_attributes[i]);
-	sysdev_remove_file(&per_cpu(device_mce,cpu), &attr_tolerant);
-	sysdev_remove_file(&per_cpu(device_mce,cpu), &attr_check_interval);
+			mce_attributes[i]);
 	sysdev_unregister(&per_cpu(device_mce,cpu));
 	memset(&per_cpu(device_mce, cpu).kobj, 0, sizeof(struct kobject));
 }
diff --git a/arch/x86_64/kernel/mce_amd.c b/arch/x86_64/kernel/mce_amd.c
index cd8dbe5..d0bd5d6 100644
--- a/arch/x86_64/kernel/mce_amd.c
+++ b/arch/x86_64/kernel/mce_amd.c
@@ -220,6 +220,10 @@ asmlinkage void mce_threshold_interrupt(void)
 			     (high & MASK_LOCKED_HI))
 				continue;
 
+			/* Log the machine check that caused the threshold
+			   event. */
+			do_machine_check(NULL, 0);
+
 			if (high & MASK_OVERFLOW_HI) {
 				rdmsrl(address, m.misc);
 				rdmsrl(MSR_IA32_MC0_STATUS + bank * 4,