Messages in this thread | | | Date | Fri, 4 Dec 2015 19:00:01 +0100 | From | Borislav Petkov <> | Subject | Re: [Patch V0] x86, mce: Ensure offline CPU's don't participate in mce rendezvous process. |
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On Fri, Dec 04, 2015 at 05:53:33PM +0000, Luck, Tony wrote: > > I don't mean that - I mean the stuff we do before we call > > cpu_is_offline() like ist_enter, this_cpu_inc(mce_exception_count), > > etc. Then we do a whole another bunch of stuff at the "out:" label like > > printk and whatnot which shouldn't run on an offlined CPU. > > ist_enter() is black magic to me. Andy? Would you be worried about executing > ist_{enter,exit}() on a cpu that was once online, but is currently marked offline > by Linux?
ist_enter() is context tracking functionality.
> Bumping mce_exception_count doesn't look like a big deal either way. It is visible in > /proc/interrupts so I'd like to keep that honest (if the cpu comes back online again). > But we could do the offline check before this. > > There will be no printk() executed in the tail of the function. after we clear MCG_STATUS > at the (new location of) the out: label we will see recover_paddr is still ~0ull and "goto done".
Whether it is kosher or not is beside the point. Why should an offlined CPU even noodle through all that code if it doesn't need/have to? It can return immediately instead.
-- Regards/Gruss, Boris.
ECO tip #101: Trim your mails when you reply.
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