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From: Bjorn Helgaas <bjorn.helgaas@hp.com>
To: Yinghai Lu <yinghai@kernel.org>
Subject: Re: [PATCH] x86: update_mptable need pci_routeirq
Date: Fri, 15 May 2009 15:52:51 -0600
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Cc: Ingo Molnar <mingo@elte.hu>, Thomas Gleixner <tglx@linutronix.de>,
       "H. Peter Anvin" <hpa@zytor.com>,
       Jesse Barnes <jbarnes@virtuousgeek.org>,
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On Friday 15 May 2009 03:13:20 pm Yinghai Lu wrote:
> Bjorn Helgaas wrote:
> > On Friday 15 May 2009 01:51:56 pm Yinghai Lu wrote:
> >> to get all device irq routing and save them
> > 
> > This changelog isn't really enough for me to understand
> > what's going on.
> > 
> >> Index: linux-2.6/arch/x86/kernel/mpparse.c
> >> ===================================================================
> >> --- linux-2.6.orig/arch/x86/kernel/mpparse.c
> >> +++ linux-2.6/arch/x86/kernel/mpparse.c
> >> @@ -17,6 +17,7 @@
> >>  #include <linux/acpi.h>
> >>  #include <linux/module.h>
> >>  #include <linux/smp.h>
> >> +#include <linux/pci.h>
> >>  
> >>  #include <asm/mtrr.h>
> >>  #include <asm/mpspec.h>
> >> @@ -961,6 +962,7 @@ static int __initdata enable_update_mpta
> >>  static int __init update_mptable_setup(char *str)
> >>  {
> >>  	enable_update_mptable = 1;
> >> +	pci_routeirq = 1;
> > 
> > I hate to see new uses of pci_routeirq.  It'd be nice to remove it
> > completely someday.  But maybe it can't be helped.
> > 
> >>  	return 0;
> >>  }
> >>  early_param("update_mptable", update_mptable_setup);
> > 
> > "update_mptable" is apparently a boot option, but it's not mentioned
> > in Documentation/kernel-parameters.txt.  Is this some sort of debug
> > code or BIOS-writer's helper?  Same with "alloc_mptable".  Why do
> > we have this stuff?
> > 
> 
> 1. kexec path: after acpi kernel and use kexec to load kerenl with mptable support only or acpi=off
> 2. help to BIOS engineer to understand how to set mptable and irq routing setup by chipset.
>    esp system have several cards and there is bridge in those cards.

I was sort of hoping for a Documentation/kernel-parameters.txt patch.

Is (1) common enough to worry about?  What OSes don't have ACPI
support?  What advantage is there to using "acpi=off"?

(2) sounds like something that should be under a config option, if
it's in the mainline kernel at all.

Bjorn