PATCH/RFC: [kdump] fix APIC shutdown sequence

[Martin Wilck]

Vivek Goyal wrote:

> But the issue here seems to be that LAPIC state got clear but IRR bit
> at IOAPIC bit is not cleared because IOAPIC vector information was deleted
> in first kernel and now upon receiving EOI, it does not know this EOI belongs
> to which vector.

I am making another experiment right now. I check the LAPIC ISR flags in
machine_crash_shutdown() before disabling the LAPIC, trying to send EOI if
I find one ISR bit set. So far, I haven't seen a single case where an ISR bit
was set, but several (9) where the IO-APIC IRR bit was set. OTOH, I know that if
I'd re-enable IRQs, IRQ 225 would be raised. The whole thing is done before
disable_IO_APIC().

Don't ask me for an explanation why I don't see the ISR bits.

The arch/x86_64/kernel/crash.c portion of the patch I am using is attached for
your reference. The rest is the same as for the original patch.

Martin

-- 
Martin Wilck
PRIMERGY System Software Engineer
FSC IP ESP DE6

Fujitsu Siemens Computers GmbH
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