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    SubjectRe: [tip:x86/debug] x86/kdump: No need to disable ioapic/ lapic in crash path
    Yinghai Lu <> writes:

    > On Sat, Feb 11, 2012 at 7:13 PM, Eric W. Biederman
    > <> wrote:
    >> Yinghai Lu <> writes:
    >>> After reverting this commit, kdump is working again.
    >>> So assume you need to drop this patch.
    >> It sounds like there is a bug in ioapic initialization in the context of
    >> VT-d.  Where do you fail?
    > before get debug print out from second kernel, the system get reset.


    Don can you work with with Yinghai to figure out what is different
    between your test configuration and his?

    YH did you have early printk enabled?

    YH Did I understand you properly that things work if you don't enable
    VT-d? By VT-d are you referring to interrupt remapping?

    For anyone watching. The premise of this patch was that we can boot
    the kernel without resorting to legacy tricks that require us to
    put the interrupt controllers in PIT mode.

    Apparently there is some weird corner case that YH can reproduce that
    Don did not have in his test set that YH does that causes things to

    I really don't see any likely candidates when looking at the code. The
    most I can see is some code that we don't run when interrupt remapping
    is enabled in disable_IO_APIC.

    So I suspect we have a bug in our apic initialization somewhere, but
    apic initialization should happen after printk are enabled. Or at least
    after early printks so the reset YH is reporting doesn't make much sense.

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