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

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Date:   Mon, 23 Jan 2017 10:01:53 -0800
From:   "Luck, Tony" <tony.luck@...el.com>
To:     Borislav Petkov <bp@...en8.de>
Cc:     xlpang@...hat.com, x86@...nel.org, linux-kernel@...r.kernel.org,
        kexec@...ts.infradead.org, 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] x86/mce: Keep quiet in case of broadcasted mce after
 system panic

On Mon, Jan 23, 2017 at 06:51:30PM +0100, Borislav Petkov wrote:
> Hey Tony,
> 
> a "welcome back" is in order? :-)

Yes - first day back today. Lots of catching up to do.

> And apparently crash knows about poisoned pages and handles them:
> 
> static int __init crash_save_vmcoreinfo_init(void)
> {
> 	...
> #ifdef CONFIG_MEMORY_FAILURE
>         VMCOREINFO_NUMBER(PG_hwpoison);
> #endif
> 
> so if that works, the kexeced kernel should know about that list.

Oh good ... it is smarter than I thought.

> Doesn't matter, right? The new copy is as clueless as the old one about
> those MCEs.

If things are well enough initialized that we don't reset, and
get to do_machine_check(), then this code from Ashok:

        /* If this CPU is offline, just bail out. */
        if (cpu_is_offline(smp_processor_id())) {
                u64 mcgstatus;

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

will ignore the machine check on the other cpus ... assuming
that "cpu_is_offline(smp_processor_id())" does the right thing
in the kexec case where this is an "old" cpu that isn't online
in the new kernel.

-Tony