linux-kernel - Re: [PATCH] x86/mce: fix failed to reenable cmci when swiching to interrupt mode

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Message-ID: <20150811144637.GA5573@nazgul.tnic>
Date:	Tue, 11 Aug 2015 16:46:37 +0200
From:	Borislav Petkov <bp@...en8.de>
To:	Xie XiuQi <xiexiuqi@...wei.com>
Cc:	tony.luck@...el.com, tglx@...utronix.de, mingo@...hat.com,
	hpa@...or.com, x86@...nel.org, linux-edac@...r.kernel.org,
	linux-kernel@...r.kernel.org, zhangliguang@...wei.com
Subject: Re: [PATCH] x86/mce: fix failed to reenable cmci when swiching to
 interrupt mode

On Tue, Aug 11, 2015 at 06:09:37PM +0800, Xie XiuQi wrote:
> Zhang Liguang report a bug as bellow:
> 1) system detected cmci storm on current cpu
> 2) disable cmci interrupt on banks ownd by current cpu, then swiching to poll mode
> 3) a few minites later, system swiching to interrupt mode on current cpu
> 4) we expect system to reenable cmci interrupt on banks ownd by current cpu
>    mce_intel_adjust_timer
>    |-> cmci_reenable
>        |-> cmci_discover     # but, ownd banks is ignore here
> 
> > static void cmci_discover(int banks)
> >	...
> >	for (i = 0; i < banks; i++) {
> >		...
> >		if (test_bit(i, owned))	# ownd banks is ignore here
> >			continue;
> 
> In this patch, we add a func cmci_storm_enable_banks(), just to enable banks
> which ownd by current cpu without clean the ownd flags. We call this func
> instead of cmci_reenble() when swiching to interrupt mode.

Hmm, and we cannot clear the owned bit because those banks won't be
polled otherwise, see:

27f6c573e0f7 ("x86, CMCI: Add proper detection of end of CMCI storms")

Yuck.

Well, ok, but do it differently, please: rename
cmci_storm_disable_banks() to cmci_storm_switch_banks(bool on) which
turns them on and off. Unless Tony has a better suggestion...

> Reported-by: Zhang Liguang <zhangliguang@...wei.com>
> Cc: stable@...r.kernel.org  # v4.1+

Why 4.1 only?

-- 
Regards/Gruss,
    Boris.

ECO tip #101: Trim your mails when you reply.
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