Re: [patch] x86, apic: use 0x20 for the IRQ_MOVE_CLEANUP_VECTOR insteadof 0x1f

From: H. Peter Anvin
Date: Wed Jan 13 2010 - 15:40:17 EST

On 01/13/2010 12:36 PM, Eric W. Biederman wrote:
> "H. Peter Anvin" <hpa@xxxxxxxxx> writes:
>> On 01/11/2010 05:52 PM, Eric W. Biederman wrote:
>>> After having the documentation quoted at me. I am having a distinct
>>> memory of one piece of documentation saying:
>>> "interrupts within a priority level can be delivered in any order"
>>> So I am guessing there is not any ordering of interrupts in the same
>>> priority level until they get to the local apic.
>> There is no ordering of interrupts before they hit the local APIC, since
>> the local APIC is what would serialize them...
> The io apic serializes them, and sends them over either the 2-wire
> bus or the front side bus. How much serialization and prioritization
> happens at that point I am not certain, but some certainly happens
> before you get to the local apic.

If you *have* a front side bus, that is! With QPI or HyperTransport,
you don't have a single serializing bus in the same way, but you have a
mesh network instead.


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