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Message-ID: <m1vdmtgtt2.fsf@fess.ebiederm.org>
Date: Thu, 18 Jun 2009 13:39:53 -0700
From: ebiederm@...ssion.com (Eric W. Biederman)
To: Jeremy Fitzhardinge <jeremy@...p.org>
Cc: Len Brown <lenb@...nel.org>, Ingo Molnar <mingo@...hat.com>,
Thomas Gleixner <tglx@...utronix.de>,
"H. Peter Anvin" <hpa@...or.com>,
the arch/x86 maintainers <x86@...nel.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Xen-devel <xen-devel@...ts.xensource.com>
Subject: Re: [PATCH RFC] x86/acpi: don't ignore I/O APICs just because there's no local APIC
Jeremy Fitzhardinge <jeremy@...p.org> writes:
> On 06/18/09 12:27, Eric W. Biederman wrote:
>>> The only actual exception I know of is Xen's replacement of the physical
>>> local APIC with a paravirtualized interrupt interface.
>>>
>>
>> No one ever has. Xen doesn't have I/O APICs either. Not in any real
>> sense. Xen just has devices that looking like I/O apics if you don't
>> look close.
>>
>
> Well, if acpi_pci_irq_lookup() and friends return the right things
> without having parsed the MADT and set up the secondary state, then we
> should be fine either way.
>
> acpi_irq_model gets tested in all sorts of random places, so I wonder if
> we'll need to set it to ACPI_IRQ_MODEL_IOAPIC (or something else?) to
> make things work properly.
And this is where things get interesting. Xen strictly speaking has
already made that decision. Unless you support non APIC mode it
should always be ACPI_IRQ_MODEL_IOAPIC.
But Xen runs the hardware so Xen knows, and Xen should be running
all of the acpi and what not to make it happen.
> Hm, and principle we just get the SCI gsi from the FADT, but there's all
> that other mucking about with it in the MADT processing... Wonder what
> needs to happen there...
Good question. What does the domU case do?
Eric
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