linux-kernel - Re: PROBLEM: mce: [Hardware Error] from dmesg -l emerg

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Date:   Mon, 21 May 2018 17:06:14 -0700
From:   "Luck, Tony" <tony.luck@...el.com>
To:     Jeffrin Thalakkottoor <jeffrin@...agiritech.edu.in>
Cc:     Borislav Petkov <bp@...en8.de>,
        Thomas Gleixner <tglx@...utronix.de>, mingo@...hat.com,
        hpa@...or.com, x86@...nel.org, linux-edac@...r.kernel.org,
        lkml <linux-kernel@...r.kernel.org>
Subject: Re: PROBLEM: mce: [Hardware Error] from dmesg -l emerg

On Tue, May 22, 2018 at 02:43:37AM +0530, Jeffrin Thalakkottoor wrote:
> mce: [Hardware Error]: CPU 0: Machine Check: 0 Bank 5: ee0000000040110b
> mce: [Hardware Error]: TSC 0 ADDR 160000080 MISC 5040008086
> mce: [Hardware Error]: PROCESSOR 0:306d4 TIME 1526932210 SOCKET 0 APIC
> 0 microcode 2a

The problem is that "mcelog --ascii" is expecting the first line to
look like:

	CPU 0: Machine Check Exception: 0 Bank 5: ee0000000040110b

This seems to have been broken by commit:

	cd9c57cad3fe ("x86/MCE: Dump MCE to dmesg if no consumers")

relevent part is this ... where we now conditionally include the
word "Exception".

-static void print_mce(struct mce *m)
+static void __print_mce(struct mce *m)
 {
-       int ret = 0;
-
-       pr_emerg(HW_ERR "CPU %d: Machine Check Exception: %Lx Bank %d: %016Lx\n",
-              m->extcpu, m->mcgstatus, m->bank, m->status);
+       pr_emerg(HW_ERR "CPU %d: Machine Check%s: %Lx Bank %d: %016Lx\n",
+                m->extcpu,
+                (m->mcgstatus & MCG_STATUS_MCIP ? " Exception" : ""),
+                m->mcgstatus, m->bank, m->status);

While this is a bit easier to read, no new information is included as we
do print the value of m->mcgstatus.

Sadly, the change was made back in v4.10 ... so reverting it won't
help all the people running kernels built in the last fifteen months :-(

I'll see if I can get Andi to take a patch for mcelog to accept the
line with or without the " Exception".

Oh ... one more thing. Did your e-mail client line wrap that last line?

> mce: [Hardware Error]: PROCESSOR 0:306d4 TIME 1526932210 SOCKET 0 APIC
> 0 microcode 2a

That should all be on one line.

-Tony