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Re: [Xen-devel] Re: APIC rework

To: "Zhang, Xiantao" <xiantao.zhang@xxxxxxxxx>, Jeremy Fitzhardinge <jeremy@xxxxxxxx>
Subject: Re: [Xen-devel] Re: APIC rework
From: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
Date: Wed, 18 Nov 2009 09:37:00 +0000
Cc: Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxx>, "Han, Weidong" <weidong.han@xxxxxxxxx>, "Jiang, Yunhong" <yunhong.jiang@xxxxxxxxx>
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Thread-topic: [Xen-devel] Re: APIC rework
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On 18/11/2009 03:25, "Zhang, Xiantao" <xiantao.zhang@xxxxxxxxx> wrote:

>> For modern dom0 don't we already assume that dom0 pirq == irq == gsi
>> (see comments in ioapic_guest_write)? Perhaps we should just have that
>> relationship set up by default: I think only NetBSD dom0 has
>> different, and it will establish different relationship via legacy
>> method of PHYSDEVOP_alloc_irq_vector and paravirtualised IOAPIC
>> writes?
> The assumption should be right for dom0 today, but it still needs to register
> this info to dom0's private data(d->arch.{pirq_irq, irq_pirq).
> And I think maybe we should clean up the logic and let hypervisor knows the
> assumption, when consulting this relationship.

Well, it strikes me that existing MAP_PIRQ_TYPE_GSI fills this role already,
as it is, doesn't it? Seems to me that is its whole purpose. :-)

Shoehorning trig/pol information into it as well is kind of nasty. And I
think on any PC system it should suffice to assume GSI 0-15 are ISA
edge-triggered active-high, GSI 16+ are PCI level-triggered active-low, and
any exceptions are parsed out of MADT or MPBIOS. We pretty much have all
that code, it just might need plumbing back in a little bit. Yunhong points
out that ACPI DSDT can have overriding objects in the _PRT, but I don't know
it ever actually gets used on real-world PC systems. So I would try without,
but if we do end up needing to get this info from dom0, I think it should be
via a new physdev_op.

 -- Keir

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