linux-kernel - Re: [PATCH 18/23] AMD IOMMU: simplify dma_mask_to

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Message-ID: <20080918073232.GB24392@amd.com>
Date:	Thu, 18 Sep 2008 09:32:32 +0200
From:	Joerg Roedel <joerg.roedel@....com>
To:	FUJITA Tomonori <fujita.tomonori@....ntt.co.jp>
CC:	linux-kernel@...r.kernel.org, iommu@...ts.linux-foundation.org
Subject: Re: [PATCH 18/23] AMD IOMMU: simplify dma_mask_to_pages

On Thu, Sep 18, 2008 at 04:20:20AM +0900, FUJITA Tomonori wrote:
> On Wed, 17 Sep 2008 18:52:52 +0200
> Joerg Roedel <joerg.roedel@....com> wrote:
> 
> > The current calculation is very complicated. This patch replaces it with
> > a much simpler version.
> > 
> > Signed-off-by: Joerg Roedel <joerg.roedel@....com>
> > ---
> >  arch/x86/kernel/amd_iommu.c |    3 +--
> >  1 files changed, 1 insertions(+), 2 deletions(-)
> 
> I think that you can use iommu_device_max_index() for what
> dma_mask_to_pages does.

Hmm, in theory yes. But iommu_device_max_index() returns a size in bytes
and not in pages. So I still need to do the page shift somewhere. This
eliminates somewhat the benefit in this particular case.

Joerg

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