Subject: Re: [PATCH v2] IA64 Compilation Error Fix for Intel IOMMU Identity
 Mapping Support
From: David Woodhouse <dwmw2@infradead.org>
To: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Cc: fenghua.yu@intel.com, chrisw@redhat.com, torvalds@linux-foundation.org,
       akpm@linux-foundation.org, tony.luck@intel.com,
       linux-kernel@vger.kernel.org, iommu@lists.linux-foundation.org,
       linux-ia64@vger.kernel.org
In-Reply-To: <20090625134827W.fujita.tomonori@lab.ntt.co.jp>
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	 <20090625095643F.fujita.tomonori@lab.ntt.co.jp>
	 <20090625041605.GA9330@linux-os.sc.intel.com>
	 <20090625134827W.fujita.tomonori@lab.ntt.co.jp>
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Date: Thu, 25 Jun 2009 08:11:26 +0100
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On Thu, 2009-06-25 at 13:48 +0900, FUJITA Tomonori wrote:
> This patch is really ugly; adds another ifdef and VT-D specific code
> to the generic place (arch/x86/kernel/pci-dma.c).
> 
> However, I guess that we need to live with this for now since this
> fixes the build error.

It raises the question: Why are we using firmware-specific interfaces to
list the available memory -- can't we get that from somewhere _generic_?

The less we tie our code to these crappy BIOS, EFI and ACPI interfaces,
the better off we'll be.

> Another complaint from me is that, IIRC, the patch causes this build
> error was posted was posted first during the merge window (18 June)
> and merged few days later without properly reviewed (or compile
> tested).

I apologise for that. I got to it rather late, just as I was reviewing
my outstanding code for Linus to pull. It _had_ been reviewed though --
this was the second incarnation of the patch, after review.

I didn't include it in my original pull request, and instead let it sit
in linux-next for a day (which is not long, I know, but better than
nothing). I then spent that day testing it myself, and tracking down a
bug in it.

I sent the fixed version to Linus at the end of the day -- I _thought_
I would have been told of any IA64 build failures in linux-next by then,
even if the original hadn't been tested on IA64 -- evidently I was
wrong.

I really must set myself up an IA64 cross-compiler. Every time I've
looked at that so far I've got distracted into the whole "why is
GCC/glibc build so incestuously broken" quagmire -- but I only need gcc,
so I'll steel myself to ignore the braindamage and just build a simple
compiler without glibc support.

Better still would be if I could find some IA64 hardware with this
IOMMU. Would kind of help with maintenance...

-- 
David Woodhouse                            Open Source Technology Centre
David.Woodhouse@intel.com                              Intel Corporation

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