linux-kernel - Re: Linux 2.6.39-rc3

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Message-ID: <BANLkTim23SQiyb4R+QA7=fpPZrnQw9_PRQ@mail.gmail.com>
Date:	Fri, 15 Apr 2011 12:11:28 -0400
From:	Jerome Glisse <j.glisse@...il.com>
To:	Joerg Roedel <joro@...tes.org>
Cc:	Ingo Molnar <mingo@...e.hu>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	"dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
	Tejun Heo <tj@...nel.org>, "H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Yinghai Lu <yinghai@...nel.org>, alexandre.f.demers@...il.com
Subject: Re: Linux 2.6.39-rc3

On Fri, Apr 15, 2011 at 11:46 AM, Joerg Roedel <joro@...tes.org> wrote:
> On Fri, Apr 15, 2011 at 03:16:50PM +0200, Ingo Molnar wrote:
>> Ok, but how did the allocation changes start triggering this error in
>> v2.6.39-rc1? There must still be some layout specific thing here, right?
>> Do we understand the details of that as well?
>
> Well, thinking again about this, the GPU likely generated this DMA
> request before too (which has an address in the range configured for the
> GTT on the card), but nobody noticed because they just hit main memory.
> And with the allocation changes in 39-rc1 the GART aperture started to
> be on the same address as the GTT (in their respective address spaces)
> so that the DMA request hit the GART. This caused the MCE and the
> sync-flood.
> The open question is why the GPU generates a DMA request with an address
> that is configured as the GTT base (+1 page) on the card.
>
>        Joerg
>

Do you also got the write if you load radeon with radeon.no_wb=1 ?
I think at this address it's the wb page, or maybe the cp as wb likely
take only one page

Cheers,
Jerome
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