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SubjectRe: [patch] x86, apic: use 0x20 for the IRQ_MOVE_CLEANUP_VECTOR instead of 0x1f
On 01/13/2010 12:36 PM, Eric W. Biederman wrote:
> "H. Peter Anvin" <hpa@zytor.com> 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.
>

From the looks of the original 82093AA spec, the 2-wire bus did
round-robin between different APICs (including IOAPICs), and the IOAPIC
had no ordering guarantees whatsoever.

-hpa



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