From fadd85f16a8ec3fee8af599e79a209682dc52348 Mon Sep 17 00:00:00 2001 From: Naoya Horiguchi Date: Mon, 23 Jan 2012 15:54:52 -0500 Subject: [PATCH] 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 Signed-off-by: Naoya Horiguchi Cc: Andi Kleen Cc: Huang Ying Link: https://lkml.org/lkml/2012/1/23/299 Signed-off-by: Tony Luck --- arch/x86/kernel/cpu/mcheck/mce.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c index 4979a5d..87c56ba 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; -- 2.7.4