linux-kernel - Re: [patch 2/2] x86: arch specific support for remapping HPET MSIs

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Date:	Mon, 10 Aug 2009 20:51:56 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Suresh Siddha <suresh.b.siddha@...el.com>
Cc:	"tglx@...utronix.de" <tglx@...utronix.de>,
	"hpa@...or.com" <hpa@...or.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"Pallipadi, Venkatesh" <venkatesh.pallipadi@...el.com>,
	David Woodhouse <dwmw2@...radead.org>,
	Jesse Barnes <jbarnes@...tuousgeek.org>,
	Jay Fenlason <fenlason@...hat.com>
Subject: Re: [patch 2/2] x86: arch specific support for remapping HPET MSIs


* Suresh Siddha <suresh.b.siddha@...el.com> wrote:

> On Sat, 2009-08-08 at 08:12 -0700, Ingo Molnar wrote:
> > * Suresh Siddha <suresh.b.siddha@...el.com> wrote:
> > 
> > > x86 arch support for remapping HPET MSI's by associating the HPET 
> > > timer block with the interrupt-remapping HW unit and setting up 
> > > appropriate irq_chip
> > 
> > interesting. This means we'd materially utilize the irq-remapper 
> > not just on relatively obscure, virtualization related setups, 
> > but also in the native x86 bootup mode, on all (hpet+remap 
> > capable) Linux systems?
> 
> Ingo, For native linux kernel, interrupt-remapping allows simple 
> and reliable irq migration from the process context (in addition 
> to its need for supporting cpu's capable of x2apic). And as such 
> solves the issues we had in the past with cpu hotplug and irq 
> migration.

It's something much more directly useful than a fix for race 
conditions, and it would be used in a broader range of hardware
than x2apic. (Not to denounce its other uses - i was just upbeat 
about it getting even more mainstream use.)

	Ingo
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