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    SubjectRe: [RFC PATCH] x86, entry: Switch stacks on a paranoid entry from userspace
    On Fri, Nov 14, 2014 at 09:56:38PM +0000, Luck, Tony wrote:
    > ...
    > But I think that means we need more than one of these structures ...
    > we may not be done with one before a new machine check occurs. So
    > we'd have to make an NMI-safe allocator to grab one for use inside
    > do_machine_check()

    Well, I think we might do something with a lockless list as it is being
    done in ghes.c.

    It allocates entries from its own pool in the NMI handler and
    llist_add's them to a list.

    Then, in user context it does llist_del_all and then looks at each of
    the elements at leisure and stress-free :-)

    Pool alloc/free is NMI-safe too so we should be good. It looks pretty
    clean, I'd give it a try.

    > General testing note - one thing I did see was that if inject 1000
    > errors at 0.3s interval from my ssh'd login ... the serial console
    > keeps streaming messages for about 40 seconds after my test says it is
    > all done. This might be a factor in the other tests I've been running
    > against the stack-switching code (especially with extra debug) ... at
    > some point __log_buf must get full - what happens then?

    Start gets overwritten AFAICR.

    --
    Regards/Gruss,
    Boris.

    Sent from a fat crate under my desk. Formatting is fine.
    --


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