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

[H. Peter Anvin]

On 01/11/2010 04:28 PM, Eric W. Biederman wrote:
> 
> Without changes assign_irq_vector will reuse vectors in the range
> IRQ0_VECTOR to IRQ15_VECTOR in the code as it we currently ship it,
> when we switch irq0-15 into ioapic mode.
> 
> Switching the loop to cover IRQ0_VECTOR to IRQ15_VECTOR is not a
> problem.  I don't think it will find anything free as we assign those
> vectors on all cpus, but the data structures are fine.
> 

The question there is if we can treat the resulting ioapic IRQs as
normal movable IRQs, and just let the target-moving mechanism take care
of it.  After all, there is a discrete event at which we decide that any
particular interrupt is an IOAPIC interrupt instead of XT-PIC.
Obviously, the vectors that remain XT-PIC vectors have to remain
allocated on all vectors for all time.

Another question is why we reserve the legacy IRQ 2 vector at all --
except when ACPI is present!  I don't think it could ever be tickled,
and it sort of felt as a "just in case" thing that could be removed.

	-hpa
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