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Date: Mon, 03 Dec 2012 00:37:05 +0100
From: Andreas Longwitz <longwitz@incore.de>
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To: Andriy Gapon <avg@FreeBSD.org>
Subject: Re: page fault on verbose boot
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>>> "Andriy Gapon wrote"
>>> Looking at the code in ioapic_program_intpin() this seems to be possible indeed:
>>>
>>> /* Write the values to the APIC. */
>>> intpin->io_lowreg = low;
>>> ioapic_write(io->io_addr, IOAPIC_REDTBL_LO(intpin->io_intpin), low);
>>>
>>> The line above reprograms vector number AND _unmasks_ the pin (which was
>>> specifically masked before reprogramming in ioapic_assign_cpu).
>>> The lines below reprogram the destination LAPIC/CPU:
>>>
>>> value = ioapic_read(io->io_addr, IOAPIC_REDTBL_HI(intpin->io_intpin));
>>> value &= ~IOART_DEST;
>>> value |= high;
>>> ioapic_write(io->io_addr, IOAPIC_REDTBL_HI(intpin->io_intpin), value);
>>>
>>> So a pending interrupt would be happily delivered to a wrong destination (new
>>> vector + old lapic).
>>> I am not sure if just swapping these two blocks of lines would fix the issue, but
>>> I hope that it would.  Could you please try that?
>> Yes I did and the first bootverbose run with your block switching patch
>> was ok. I will do some more expansive tests next week.
> 
> Thank you very much.
> I've committed this change to head.

After several tests I can state: the patch is ok for me.

Thanks for your quick help!


-- 
Andreas Longwitz