linux-kernel - Re: Intel IOMMU (and IOMMU for Virtualization) performances

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Message-ID: <20080609102025.GB21661@one.firstfloor.org>
Date:	Mon, 9 Jun 2008 12:20:25 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	FUJITA Tomonori <fujita.tomonori@....ntt.co.jp>
Cc:	andi@...stfloor.org, grundler@...gle.com, muli@...ibm.com,
	linux-kernel@...r.kernel.org, mgross@...ux.intel.com,
	linux-scsi@...r.kernel.org
Subject: Re: Intel IOMMU (and IOMMU for Virtualization) performances

On Mon, Jun 09, 2008 at 06:36:29PM +0900, FUJITA Tomonori wrote:
> On Mon, 09 Jun 2008 10:17:11 +0200
> Andi Kleen <andi@...stfloor.org> wrote:
> 
> > "Grant Grundler" <grundler@...gle.com> writes:
> > >
> > > The historical DMA mapping "failure mode" is a kernel panic.  Resizing or
> > 
> > Hasn't been for a long time, except in some extreme cases.  All drivers
> > are expected to check return values for a long time now.
> 
> Agreed, but I think that lots of network drivers still assume that DMA
> mapping always succeeds (they don't check return values).

Those should be just fixed. 

You're right. I reviewed some new drivers and was surprised that they
even got that wrong (code reviewers were supposed to flag this in the
first place)

I would guess in practice the main offender would be tg3.c/bnx2.c.
On the other hand Intel IOMMU systems should usually use e1000e which
checks.

-Andi
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