linux-kernel - Re: [PATCH 01/34] AMD IOMMU: add Kconfig entry

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Message-ID: <20080628105240.GI10197@8bytes.org>
Date:	Sat, 28 Jun 2008 12:52:40 +0200
From:	Joerg Roedel <joro@...tes.org>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	Muli Ben-Yehuda <muli@...ibm.com>, Adrian Bunk <bunk@...nel.org>,
	Joerg Roedel <joerg.roedel@....com>, tglx@...utronix.de,
	mingo@...hat.com, linux-kernel@...r.kernel.org,
	iommu@...ts.linux-foundation.org, bhavna.sarathy@....com,
	Sebastian.Biemueller@....com, robert.richter@....com
Subject: Re: [PATCH 01/34] AMD IOMMU: add Kconfig entry

On Fri, Jun 27, 2008 at 08:54:59PM +0200, Andi Kleen wrote:
> Joerg Roedel <joro@...tes.org> writes:
> 
> > On Fri, Jun 27, 2008 at 12:39:45PM -0400, Muli Ben-Yehuda wrote:
> >> On Fri, Jun 27, 2008 at 04:47:29PM +0200, Andi Kleen wrote:
> >> 
> >> > Also it should ideally describe that there is a trade off between
> >> > reliability and performance with IOMMU enabled.
> >> 
> >> I agree that there's a performance tradeoff with current generation
> >> hardware and ingerfaces, but it wouldn't be fair to single out a
> >> single IOMMU implementation ;=)
> >
> > True. At least for the case without device isolation I have some
> > optimizations in mind which will minimize the performance tradeoff. I
> > hope to have them ready for 2.6.28 :)
> 
> Not sure that would be very useful. Outside of virtualization device
> isolation is the main feature of an IOMMU on a native kernel.

I agree that device isolation is one of the a main usage scenarios for
an IOMMU. But if somebody want to use it for virtualization and doesn't
need device isolation this optimization would be usefull.

Joerg

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