linux-kernel - Re: [PATCH v2] x86/mce: Don't participate in rendezvous process once nmi_shootdown

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Date:   Tue, 21 Feb 2017 09:28:20 +0800
From:   Xunlei Pang <xpang@...hat.com>
To:     Borislav Petkov <bp@...en8.de>, xlpang@...hat.com
Cc:     x86@...nel.org, linux-kernel@...r.kernel.org,
        kexec@...ts.infradead.org, Tony Luck <tony.luck@...el.com>,
        Ingo Molnar <mingo@...hat.com>, Dave Young <dyoung@...hat.com>,
        Prarit Bhargava <prarit@...hat.com>,
        Junichi Nomura <j-nomura@...jp.nec.com>,
        Kiyoshi Ueda <k-ueda@...jp.nec.com>,
        Naoya Horiguchi <n-horiguchi@...jp.nec.com>
Subject: Re: [PATCH v2] x86/mce: Don't participate in rendezvous process once
 nmi_shootdown_cpus() was made

On 02/21/2017 at 04:26 AM, Borislav Petkov wrote:
> On Mon, Feb 20, 2017 at 09:29:24PM +0800, Xunlei Pang wrote:
>> There is a small window between crash and kdump kernel boot, so
>> if a SRAO comes within this window it will also cause the mce
>> synchronization problem on the crashing cpu if we don't bail out the
>> crashing cpu.
> You mean, in the window between, kdump kernel starts writing out memory
> and the second, kexec-ed kernel?

Not kdump kernel starts dumping, just during nmi_shootdown_cpus(), if some
MCE comes after crashing_cpu was set and we don't skip crashing_cpu, then
the crashing cpu will enter mce handler and trigger the synchronization issue.

>
> If so, please add that information to the place in do_machine_check()
> where we check crashing_cpu so that we know why we're doing this
> temporary ignore of #MC.

Ok, will add, thanks for the feedback.

Regards,
Xunlei