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

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Date:   Sat, 18 Feb 2017 00:21:42 +0800
From:   Xunlei Pang <xpang@...hat.com>
To:     Borislav Petkov <bp@...en8.de>, xlpang@...hat.com
Cc:     Prarit Bhargava <prarit@...hat.com>,
        Kiyoshi Ueda <k-ueda@...jp.nec.com>,
        Tony Luck <tony.luck@...el.com>,
        Peter Zijlstra <peterz@...radead.org>, x86@...nel.org,
        kexec@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Ingo Molnar <mingo@...hat.com>,
        Junichi Nomura <j-nomura@...jp.nec.com>,
        Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
        Dave Young <dyoung@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH] x86/mce: Keep quiet in case of broadcasted mce after
 system panic

On 02/17/2017 at 05:07 PM, Borislav Petkov wrote:
> 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;
> 		}
> 	}

Yes, it is doable, I will do some tests later.

>> 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".
>

It's from my understanding, I didn't get the explicit description from the intel SDM on this point.
If a broadcast SRAO comes on real hardware, will MSR_IA32_MCG_STATUS of each cpu have MCG_STATUS_RIPV bit set?

Regards,
Xunlei