From: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Date: Mon, 23 Jan 2012 20:54:52 +0000 (-0500)
Subject: x86/mce: Fix return value of mce_chrdev_read() when erst is disabled
X-Git-Tag: firefly_0821_release~3680^2~3311^2^2
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=fadd85f16a8ec3fee8af599e79a209682dc52348;p=firefly-linux-kernel-4.4.55.git

x86/mce: Fix return value of mce_chrdev_read() when erst is disabled

Current kernel MCE code reads ERST at the first reading of /dev/mcelog
(maybe in starting mcelogd,) even if the system does not support ERST,
which results in a fake "no such device" message (as described in [1].)
This problem is not critical, but can confuse system admins.
This patch fixes it by filtering the return value from lower (ACPI) layer.

 [1] http://thread.gmane.org/gmane.linux.kernel/1060250

Reported by: Jon Masters <jonathan@jonmasters.org>
Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Huang Ying <ying.huang@intel.com>
Link: https://lkml.org/lkml/2012/1/23/299
Signed-off-by: Tony Luck <tony.luck@intel.com>
---

diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c
index 4979a5dfeba2..87c56ba8080c 100644
--- a/arch/x86/kernel/cpu/mcheck/mce.c
+++ b/arch/x86/kernel/cpu/mcheck/mce.c
@@ -1541,6 +1541,12 @@ static int __mce_read_apei(char __user **ubuf, size_t usize)
 	/* Error or no more MCE record */
 	if (rc <= 0) {
 		mce_apei_read_done = 1;
+		/*
+		 * When ERST is disabled, mce_chrdev_read() should return
+		 * "no record" instead of "no device."
+		 */
+		if (rc == -ENODEV)
+			return 0;
 		return rc;
 	}
 	rc = -EFAULT;