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    SubjectRe: [Xen-devel] [PATCH 1/3] xen/mce: Add mcelog support for Xen platform (v2)
    On Fri, May 25, 2012 at 05:56:56PM +0000, Liu, Jinsong wrote:
    > Konrad Rzeszutek Wilk wrote:
    > >>>>>> -static struct miscdevice mce_chrdev_device = {
    > >>>>>> +struct miscdevice mce_chrdev_device = {
    > >>>>>> MISC_MCELOG_MINOR,
    > >>>>>> "mcelog",
    > >>>>>> &mce_chrdev_ops,
    > >>>>>
    > >>>>> You're still reusing those - pls, define your own 'struct
    > >>>>> miscdevice mce_chrdev_device' in drivers/xen/ or somewhere
    > >>>>> convenient and
    > >>>>> your own mce_chrdev_ops. The only thing you should be touching in
    > >>>>> arch/x86/.../mcheck/ is the export of MISC_MCELOG_MINOR.
    > >>>>>
    > >>>>> Thanks.
    > >>>>
    > >>>> I'm *not* reuse native code.
    > >>>> I have defined 'struct miscdevice xen_mce_chrdev_device' in
    > >>>> drivers/xen, and I also implement xen_mce_chrdev_ops, they are all
    > >>>> xen-self-contained.
    > >>>>
    > >>>> The patch just redirect native mce_chrdev_device to
    > >>>> xen_mce_chrdev_device when running under xen environment.
    > >>>> It didn't change any native code (except just cancel
    > >>>> mce_chrdev_device 'static'), and will not break native logic.
    > >>>
    > >>> Why are you doing that?
    > >>>
    > >>> Why don't you do
    > >>>
    > >>> misc_register(&xen_mce_chrdev_device);
    > >>>
    > >>> in xen_early_init_mcelog() ?
    > >>>
    > >>> This way there'll be no arch/x86/ dependencies at all.
    > >>
    > >> The reason is, if we do so, it would be covered by native
    > >> misc_register(&mce_chrdev_device) later when native kernel init (xen
    > >> init first and then start native kernel).
    > >
    > > Won't the second registration (so the original one) of the major
    > > fail? So the mce_log would just error out since somebody already
    > > registered?
    >
    > No, that would be device confliction, the 2nd register return as -EBUSY and un-predicetable result.

    And the existing code does not actually check the 'misc_register' return
    value? Ah yes. Perhaps then a fix to arch/x86/kernel/cpu/mcheck/mce.c to
    do the proper de-registration if 'misc_register' fails?

    Or just set 'mce_disabled=1' in the bootup of Xen, similar to
    how lguest.c does it?

    > I test it in your way, mcelog fail to fetch any error log.

    And that is b/c of? What exactly?
    >
    > Thanks,
    > Jinsong


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