linux-kernel - Re: [PATCH 0/16] DMA-API debugging facility v2

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Message-ID: <20090206182052.GI27684@sequoia.sous-sol.org>
Date:	Fri, 6 Feb 2009 10:20:52 -0800
From:	Chris Wright <chrisw@...s-sol.org>
To:	David Woodhouse <dwmw2@...radead.org>
Cc:	Chris Wright <chrisw@...s-sol.org>,
	Joerg Roedel <joerg.roedel@....com>,
	fujita.tomonori@....ntt.co.jp, netdev@...r.kernel.org,
	iommu@...ts.linux-foundation.org, mingo@...hat.com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/16] DMA-API debugging facility v2

* David Woodhouse (dwmw2@...radead.org) wrote:
> An alternative explanation... The DMA is aborted¹, and the device
> interrupts us to tell us about it at the _same_ time that the IOMMU
> interrupts us to tell us about the fault. We process the device
> interrupt first, unmap that buffer. And then we process the IOMMU
> interrupt... and the buffer is already gone from the list.

[  362.283661] Device 0000:03:00.0 mapping: 1000@...1b000
[  362.283727] DMAR:[DMA Write] Request device [03:00.0] fault addr fff1b000 
[  362.284719] Device 0000:03:00.0 unmapping: 1000@...1b000

[  362.426974] Device 0000:03:00.0 mapping: 1000@...1b000
[  362.427040] DMAR:[DMA Write] Request device [03:00.0] fault addr fff1b000 
[  362.429092] Device 0000:03:00.0 unmapping: 1000@...1b000

[  447.644332] Device 0000:03:00.0 mapping: 1000@...03000
[  447.644373] DMAR:[DMA Write] Request device [03:00.0] fault addr fff03000 
[  447.646008] Device 0000:03:00.0 unmapping: 1000@...03000

[  483.037641] Device 0000:03:00.0 mapping: 1000@...9f000
[  483.037707] DMAR:[DMA Write] Request device [03:00.0] fault addr ffc9f000 
[  483.038699] Device 0000:03:00.0 unmapping: 1000@...9f000

...

Looks like driver is doing the right thing.
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