linux-kernel - Re: [PATCH] iommu: moving initialization earlier

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Message-ID: <CAKocOOOzzpN_ZdN9owv5tb-28qtvXc9KvF7WuyZdxYrAYxnNTw@mail.gmail.com>
Date:	Fri, 11 Jan 2013 09:56:20 -0700
From:	Shuah Khan <shuahkhan@...il.com>
To:	Joerg Roedel <joro@...tes.org>
Cc:	Alexey Kardashevskiy <aik@...abs.ru>,
	Joerg Roedel <joerg.roedel@....com>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	linux-kernel@...r.kernel.org, iommu@...ts.linux-foundation.org,
	Shuah Khan <shuah.khan@...com>
Subject: Re: [PATCH] iommu: moving initialization earlier

On Fri, Jan 11, 2013 at 7:50 AM, Joerg Roedel <joro@...tes.org> wrote:
> On Thu, Jan 10, 2013 at 01:40:17PM -0700, Shuah Khan wrote:
>> I am currently debugging IO_PAGE_FAULTS on 3.6.11 (happens on all
>> pre-3.7 releases). I root-caused the reason 3.7 works is because in
>> 3.7 amd iommu driver moving up the early iommu initialization from
>> irq_remap_ops with the irq remapping feature.
>
> Have you investigated the reason for those IO_PAGE_FAULTS? I guess they
> come from the USB controlers and happen between the time the IOMMU is
> enabled and the USB controlers are taken over by the Linux kernel from
> the BIOS.
>
> But I don't see why this patch can have any impact on the IO_PAGE_FAULTS
> you are seeing.

USB is one of them and SATA is another. I know with my back-port to
split dma ops initialization and this patch Alexey sent, the problem
goes away on 3.6.11 and I don't see the problem on 3.7. Same system,
and two different boots. I will investigate do more investigation into
the nature of these faults I am seeing and get back to you.

Thanks,
-- Shuah
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