linux-kernel - Re: [PATCH] x86/mce: Keep quiet in case of broadcasted mce after system panic

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Date:   Fri, 17 Feb 2017 10:07:35 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     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>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH] x86/mce: Keep quiet in case of broadcasted mce after
 system panic

On Fri, Feb 17, 2017 at 09:53:21AM +0800, Xunlei Pang wrote:
> It changes the value of cpu_online_mask/etc which will cause confusion to vmcore analysis.

Then export the crashing_cpu variable, initialize it to something
invalid in the first kernel, -1 for example, and test it in the #MC
handlier like this:

	int cpu;

	...

	cpu = smp_processor_id();

	if (cpu_is_offline(cpu) ||
	    ((crashing_cpu != -1) && (crashing_cpu != cpu)) {
                u64 mcgstatus;

                mcgstatus = mce_rdmsrl(MSR_IA32_MCG_STATUS);
                if (mcgstatus & MCG_STATUS_RIPV) {
                        mce_wrmsrl(MSR_IA32_MCG_STATUS, 0);
			return;
		}
	}

> Moreover, for the code(see comment inlined)
> 
>         if (cpu_is_offline(smp_processor_id())) {
>                 u64 mcgstatus;
> 
>                 mcgstatus = mce_rdmsrl(MSR_IA32_MCG_STATUS);
>                 if (mcgstatus & MCG_STATUS_RIPV) { // This condition may be not true, the mce triggered on kdump cpu 
>                                                                      // doesn't need to have this bit set for the other cpus remain in 1st kernel. 

Is this on kvm or on a real hardware? Because for kvm I don't care. And
don't say "theoretically".

-- 
Regards/Gruss,
    Boris.

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