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

[Luck, Tony]

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