linux-kernel - Re: [PATCH 03/28] x86/irq: Use irq_remap specific print_IO

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Message-ID: <20120706130530.GC2639@amd.com>
Date:	Fri, 6 Jul 2012 15:05:30 +0200
From:	Joerg Roedel <joerg.roedel@....com>
To:	Ingo Molnar <mingo@...nel.org>
CC:	<iommu@...ts.linux-foundation.org>, <linux-kernel@...r.kernel.org>,
	<x86@...nel.org>, Yinghai Lu <yinghai@...nel.org>,
	Suresh Siddha <suresh.b.siddha@...el.com>
Subject: Re: [PATCH 03/28] x86/irq: Use irq_remap specific print_IO_APIC
 paths only on Intel

On Fri, Jul 06, 2012 at 10:50:36AM +0200, Ingo Molnar wrote:
> 
> * Joerg Roedel <joerg.roedel@....com> wrote:
> >  extern int irq_remapping_enabled;
> > +extern int intel_irq_remap_debug;

> Instead of yet another set of global flags thrown around the 
> kernel please properly factor out this code, its data structures 
> and methods: introduce a single descriptor structure that 
> describes this piece of hardware, with debugging flags part of 
> this structure - with operations function pointer structure and 
> such.

Not sure I understand what you mean. So, simplified, from a hardware
point of view we have IO-APICs and MSIs. This doesn't change with
IOMMU-based interrupt remapping. The IO-APICs and MSIs are properly
abstraced through 'struct irq_chip'.

When an IOMMU comes into play the IO-APICs and MSIs need to be
programmed differently so that they send the IRQ messages in a way the
IOMMU can remap. This is done by using a different 'struct irq_chip'
when interrupt remapping is enabled.

For IRQ remapping there are two (not so much) different implementations
which are abstracted through 'struct irq_remap_ops' made accessible via
functions.

So what I _think_ you mean is to add another call-back to the
irq_remap_ops to print out debugging information and use that call-back
when IRQ remapping is enabled instead of the routine in io_apic.c. Is
that right?

Regards,

	Joerg

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