trace, eMCA: Add a knob to adjust where to save event log

To avoid saving two copies for one H/W event, add a new
file under debugfs to control how to save event log.
Once this file is opened, the perf/trace will be used,
in the meanwhile, kernel will stop printing event log
to the console. On the other hand, if this file is closed,
kernel will print event log to the console again.
Signed-off-by: NChen, Gong <gong.chen@linux.intel.com>
Acked-by: NBorislav Petkov <bp@suse.de>
Signed-off-by: NTony Luck <tony.luck@intel.com>

drivers/acpi/acpi_extlog.c

@@ -12,6 +12,7 @@
 #include <linux/cper.h>
 #include <linux/ratelimit.h>
 #include <linux/edac.h>
+#include <linux/ras.h>
 #include <asm/cpu.h>
 #include <asm/mce.h>
 
@@ -154,7 +155,11 @@ static int extlog_print(struct notifier_block *nb, unsigned long val,
 	estatus->block_status = 0;
 
 	tmp = (struct acpi_generic_status *)elog_buf;
-	print_extlog_rcd(NULL, tmp, cpu);
+
+	if (!ras_userspace_consumers()) {
+		print_extlog_rcd(NULL, tmp, cpu);
+		goto out;
+	}
 
 	/* log event via trace */
 	err_seq++;
@@ -171,6 +176,7 @@ static int extlog_print(struct notifier_block *nb, unsigned long val,
 					       (u8)gdata->error_severity);
 	}
 
+out:
 	return NOTIFY_STOP;
 }