Re: [Xen-devel] RE: [PATCH] Don't free irqaction for com irq when release irq.

[Jeremy Fitzhardinge <jeremy@xxxxxxxx>]

On 09/03/09 05:53, Zhang, Xiantao wrote:
> I think Jan also answered your question.   Dom0 shouldn't touch ioapic after 
> initialization time any more.  That is to say, maybe we can find a way to get 
> rid of ioapic from dom0.  Actually I can't see why dom0 cares so much about 
> ioapic.   Jeremy, do you know the reason ?  IMO, dom0 should only cares about 
> GSI and pirq mapping, but currently GSI is always equal to pirq in dom0, so 
> no reason to keep ioapic in dom0. 
>   

Yes, I agree.  I have a prototype branch:
git://git.kernel.org/pub/scm/linux/kernel/git/jeremy/xen.git
#rebase/dom0/new-interrupt-routing which replaces the whole interrupt
handing subsystem to avoid any direct interactions with the IO APICs.

I add a new hypercall to directly bind a gsi to a given pirq (which has
some similarities to your patch).  I've attached it below. 
(new-interrupt-routing shouldn't need this patch to function, however.)

Unfortunately I haven't had a chance to work on this lately, but when I
last tried it, it hung shortly after initializing ACPI.  I didn't get
much further than that.  I do think, however, that this is this right
way to go for dom0, esp with regard to upstreaming.

(The second patch is to allow dom0 to get Xen's acpi interrupt model so
they can always be consistent rather than independently arriving at the
same result - not not.)

    J

Attachment: xen-new-ioapic.patch
Description: Text Data

Attachment: xen-acpi-irq-model.patch
Description: Text Data

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