linux-kernel - Re: [PATCH 0/7] Boot IRQ quirks and rerouting

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Date:	Tue, 3 Jun 2008 12:11:43 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Olaf Dabrunz <od@...e.de>
cc:	Ingo Molnar <mingo@...e.hu>, "H. Peter Anvin" <hpa@...or.com>,
	Jon Masters <jonathan@...masters.org>,
	Stefan Assmann <sassmann@...e.de>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 0/7] Boot IRQ quirks and rerouting

Olaf,

On Mon, 2 Jun 2008, Olaf Dabrunz wrote:
> These patches are against linux-2.6-tip, auto-x86-next.
> 
> When IRQ lines on secondary or higher IO-APICs are masked (as done by
> RT and others), many chipsets redirect IRQs on this line to the PIC, and
> thereby regularly to the first IO-APIC in the system. This causes
> spurious interrupts and can lead to disabled IRQ lines.
> 
> Disabling this "boot interrupt" (as it is mostly used to supply all
> IRQs to the legacy PIC during boot) is chipset-specific, and not
> possible for all chips. This patchset disables the boot interrupt on
> chipsets where this is possible and where we know how to do it.
> 
> When disabling the boot interrupt is not possible, the patches tell the
> IRQ code to always use the redirected interrupt line (on the first
> IO-APIC) instead of the "original" line on the secondary (tertiary ...)
> IO-APIC. The original line remains masked, and IRQs always appear on
> the boot interrupt line on the first IO-APIC instead.

Thanks for doing the research on this problem. 

We probably don't want to enable this unconditionally right away, so
we should have a command line option which enables these quirks.

Also is there any interaction with MSI ?

Thanks,
	tglx
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