linux-kernel - Re: [RFC patch] init default dma_ops to prepare intel_iommu

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Message-Id: <20090813175921J.fujita.tomonori@lab.ntt.co.jp>
Date:	Thu, 13 Aug 2009 18:00:31 +0900
From:	FUJITA Tomonori <fujita.tomonori@....ntt.co.jp>
To:	dwmw2@...radead.org
Cc:	luming.yu@...il.com, fujita.tomonori@....ntt.co.jp,
	fenghua.yu@...el.com, tony.luck@...el.com,
	linux-kernel@...r.kernel.org, akpm@...ux-foundation.org
Subject: Re: [RFC patch] init default dma_ops to prepare intel_iommu_init 
 failure

On Thu, 13 Aug 2009 09:49:33 +0100
David Woodhouse <dwmw2@...radead.org> wrote:

> On Thu, 2009-08-13 at 16:11 +0800, Luming Yu wrote:
> > I treat this as -32 or -33 stuff, because I don't see a real system is blocking
> > on the problem. I found this problem when I was trying to disable some drhd
> > for debugging a real iommu issue...that one has priority.
> 
> (The real bug you were chasing is fixed, isn't it? Or worked around, at
> least, since the BIOS in question is still closed source and broken.)
> 
> But by talking about disabling _some_ drhd units, you've just reminded
> me that the problem is far more interesting -- we can have the IOMMU
> active for _some_ devices but not others.

It's very common. X86, POWER, IA64 can handle it (I might overlook
some).

About X86, Calgary IOMMU uses both archdata.dma_ops and the global
dma_ops.


> I was toying with the idea of putting the intel_dma_ops into
> dev->archdata for each pci device at boot or hotplug time, and leaving
> the global variable alone. We can calculate the dev->iommu mapping at
> that point too. And we can stop being quite so broken w.r.t. PCI
> hotplug...
> 
> -- 
> David Woodhouse                            Open Source Technology Centre
> David.Woodhouse@...el.com                              Intel Corporation
> 
> --
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