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RE: [Xen-devel] hardware interrupt


  • To: "Daniel Stodden" <stodden@xxxxxxxxxx>
  • From: "Agarwal, Lomesh" <lomesh.agarwal@xxxxxxxxx>
  • Date: Tue, 23 Oct 2007 20:26:13 -0700
  • Cc: Xen Developers <xen-devel@xxxxxxxxxxxxxxxxxxx>
  • Delivery-date: Tue, 23 Oct 2007 20:26:55 -0700
  • List-id: Xen developer discussion <xen-devel.lists.xensource.com>
  • Thread-index: AcgV4edhSAQLvHXqQWawLj4d1cn2ZgAC1qCg
  • Thread-topic: [Xen-devel] hardware interrupt

Are hardware interrupts programmed to be delivered in round robin fashion in 
Xen? If yes then interrupt from a particular device can go to different 
processor.

-----Original Message-----
From: Daniel Stodden [mailto:stodden@xxxxxxxxxx] 
Sent: Tuesday, October 23, 2007 7:02 PM
To: Agarwal, Lomesh
Cc: Xen Developers
Subject: Re: [Xen-devel] hardware interrupt


On Tue, 2007-10-23 at 15:57 -0700, Agarwal, Lomesh wrote:
> Is there a way I can find out on which physical processor I am receiving
> interrupt from a particular device? 

if you know the irq number.

the path taken on irqs is roughly IRQ0x**_interrupt -> common_interrupt
-> do_IRQ() (C, finally), then back to guest context via ret_from_intr.
see the definition of BUILD_COMMON_INTERRUPT() and related.

if it's bound, it will visit send_guest_pirq().

as far as i know, the physical cpu does not leak to guest context, so
it's going to be the VMM.

you get the physical cpu number via smp_processor_id().

> Can I put prints somewhere in Xen to
> do that?

printk in irq context isn't exactly scalable, but you'll might just get
away with it.

hth,
daniel

-- 
Daniel Stodden
LRR     -      Lehrstuhl für Rechnertechnik und Rechnerorganisation
Institut für Informatik der TU München             D-85748 Garching
http://www.lrr.in.tum.de/~stodden         mailto:stodden@xxxxxxxxxx
PGP Fingerprint: F5A4 1575 4C56 E26A 0B33  3D80 457E 82AE B0D8 735B

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