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    SubjectRe: [PATCH 2/2] x86: re-enable MCE on secondary CPUS after suspend/resume
    On Fri, Dec 12, 2008 at 08:06:21PM +0100, Andi Kleen wrote:
    > Andreas Herrmann <> writes:
    > > Impact: fix suspend/resume bug with MCE
    > >
    > > After suspend/resume MCx_CTL registers of secondary CPUs are cleared.
    > > (At least that's what I've observed on several systems.)
    > > Linux currently only re-initializes MCE on the boot CPU - see mce_resume().
    > > Thus after suspend/resume we end up with a system where MCE is active
    > > on the boot CPU but switched off on all other CPUs.
    > >
    > > By calling mce_init() whenever a CPU comes online this problem is
    > > solved.
    > Can you double check that please?
    > Suspend/resume are supposted to hotunplug all CPUs except the BP and
    > then re-online them on resume (with "disable_nonboot_cpus()) . The
    > re-online initializes MCEs in the standard CPU bootup path.

    For BP we have

    /* On resume clear all MCE state. Don't want to see leftovers from the BIOS.
    Only one CPU is active at this time, the others get readded later using
    CPU hotplug. */
    static int mce_resume(struct sys_device *dev)
    return 0;

    For APs mcheck_init() is called on resume. But as the respective bit
    for an AP is usually set in "mce_cpus" after boot (which is correct, I
    think) mcheck_init does not call mce_init, see:

    void __cpuinit mcheck_init(struct cpuinfo_x86 *c)
    static cpumask_t mce_cpus = CPU_MASK_NONE;


    if (mce_dont_init ||
    cpu_test_and_set(smp_processor_id(), mce_cpus) ||
    => return;


    But we need to call mce_init to clear all MCE state.
    IMHO the best location to call mce_init for APs is the cpu notifier.



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