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

From: H. Peter Anvin
Date: Mon Jan 11 2010 - 19:14:42 EST

On 01/11/2010 04:06 PM, Suresh Siddha wrote:
>> Yes, that's what I said. My question was to Suresh what enforces that
>> in the case of his patch, which moves the legacy range into the middle
>> of the device vectors.
> It's not the used_vector bitmap. That range will appear as used on all
> the cpu's and hence we won't be allocating it for anything else.

OK, fair enough.

> Now the question is: for non-legacy (io-apic) case, instead of reserving
> this range for all the cpu's, does it make sense to generalize like any
> other vector?

It sounds like something that we could experiment with -- after
switching an IRQ to ioapic mode, make it a movable interrupt. It
*seems* it should work, but it's scary stuff to muck with.

Eric, do you see any reason why it wouldn't work? I truly couldn't
understand your previous remark, especially the bit about "it is
dangerous to play lowest priority irq games in that range".


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