[<prev] [next>] [<thread-prev] [day] [month] [year] [list]
Message-ID: <m1vdx3hiio.fsf@frodo.ebiederm.org>
Date: Wed, 10 Sep 2008 13:07:27 -0700
From: ebiederm@...ssion.com (Eric W. Biederman)
To: Jeremy Fitzhardinge <jeremy@...p.org>
Cc: Yinghai Lu <yhlu.kernel@...il.com>, Ingo Molnar <mingo@...e.hu>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: TARGET_CPUS in assign_irq_vector
Jeremy Fitzhardinge <jeremy@...p.org> writes:
> Hm. That would work OK for fully paravirtualized domains, which have no
> direct access to real hardware in any form (well, there's pci
> passthough, but interrupts are all thoroughly massaged into event channels).
>
> But for dom0, the kernel handles interrupts weird hybrid mode. The
> interrupts themselves are delivered via event channels rather than via a
> local apic, but the IO APIC is still under the kernel's control, and is
> responsible for poking (Xen-allocated) vectors into it. This only
> applies to physical irq event channels; there's no need to have vectors
> for purely software event channels like interdomain, IPI and timers.
> This is further complicated by the fact that the dom0 kernel parses the
> ACPI and MPTABLES to find out about IO APICs, so the existing APIC
> subsystem is already involved. I need to work out how'd I'd hook all
> this together with a minimum of mess.
In that case. Having the information on the event channel tell you
which cpu and which vector were received is sufficient. Then you
can call into do_IRQ() with the information. Unless ack_irq()
and friends are enough different at the local apic level to cause
a challenge.
For the reset of the event channel interrupts you simply want to
dispatch the irq directly.
Eric
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists