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Date: Thu, 25 Feb 2010 07:49:17 -0500
From: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
To: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Cc: chrisw@sous-sol.org, jeremy@goop.org, Ian.Campbell@eu.citrix.com,
       linux-kernel@vger.kernel.org, iommu@lists.linux-foundation.org,
       dwmw2@infradead.org, alex.williamson@hp.com
Subject: Re: [PATCH 02/10] swiotlb: Make 'setup_io_tlb_npages' accept new
	'swiotlb=' syntax.
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On Thu, Feb 25, 2010 at 03:53:20PM +0900, FUJITA Tomonori wrote:
> On Thu, 18 Feb 2010 11:26:58 -0500
> Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> wrote:
> 
> > The old syntax for 'swiotlb' is still in effect, and we extend it
> > now to include the overflow buffer size. The syntax is now:
> > 
> > swiotlb=[force,][nslabs=<pages>,][overflow=<size>] or more
> > commonly know as:
> > 
> > swiotlb=[force]
> > swiotlb=[nslabs=<pages>]
> > swiotlb=[overflow=<size>]
> > 
> > Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
> > ---
> >  Documentation/x86/x86_64/boot-options.txt |    6 ++++-
> >  lib/swiotlb.c                             |   36 +++++++++++++++++++++++++---
> >  2 files changed, 37 insertions(+), 5 deletions(-)
> 
> 'overflow' is a workaround for broken drivers (that ignores DMA
> mapping errors). We have fixed such drivers and other hardware IOMMU
> implementations don't have such workaround. So please don't extend
> it. We should remove it instead.

Will do. Do you remember which drivers (or e-mail threads) exhibited this
behavior so that I can do a regression test to make absolutely certain
that removing the overflow functionality won't blow something up?

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