linux-kernel - Re: [PATCH v8] x86: mce: kexec: switch MCE handler for kexec/kdump

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Date:	Thu, 9 Apr 2015 09:02:45 +0200
From:	Borislav Petkov <bp@...en8.de>
To:	Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
	Tony Luck <tony.luck@...el.com>
Cc:	Ingo Molnar <mingo@...nel.org>,
	Prarit Bhargava <prarit@...hat.com>,
	Vivek Goyal <vgoyal@...hat.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Junichi Nomura <j-nomura@...jp.nec.com>,
	Kiyoshi Ueda <k-ueda@...jp.nec.com>
Subject: Re: [PATCH v8] x86: mce: kexec: switch MCE handler for kexec/kdump

On Thu, Apr 09, 2015 at 06:57:38AM +0000, Naoya Horiguchi wrote:
> Yes, I did see it at fisrt, so I did two tweaks for the testing:
> 
> 1) to fix qemu code. I think that current mce injection code of qemu is buggy,
> because when we try to inject MCE in broadcast mode, all injections other than
> the first one are done with MCG_STATUS_MCIP (see cpu_x86_inject_mce()@target-i386/helper.c.)
> It looks to me a bug because this means that every (broadcast mode) MCE injection
> causes triplet-fault, which seems not mimicking the real HW behavior.
> 
> 2) to insert the delay (for a few seconds) into kdump_nmi_callback() before
> disable_local_APIC(). This is because MCE interrupt is delivered to CPUs in
> different manners in qemu and in bare metal. Bare metals do respond to MCE
> interrupts after disable_local_APIC(), but qemu not.

Lemme take a look at that.

> Unfortunately our testing (~15000 times kdump/reboot cycles) with the debug
> kernel on bare metals didn't reproduce the problem yet, but I believe that
> the above testing on qemu should hit a target.

If only APEI EINJ could be taught to do delayed injection, regardless of
OS kernel running. Tony, is something like that even possible at all?

-- 
Regards/Gruss,
    Boris.

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