linux-kernel - Re: ATA device reset, shoud I be concerned?

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Date:	Wed, 26 Aug 2009 23:07:01 -0400
From:	Jeff Garzik <jeff@...zik.org>
To:	Robert Hancock <hancockrwd@...il.com>
CC:	Tejun Heo <htejun@...il.com>, Alan Cox <alan@...rguk.ukuu.org.uk>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Georgi Chulkov <g.chulkov@...obs-university.de>,
	linux-kernel@...r.kernel.org, linux-ide@...r.kernel.org,
	Mark Lord <liml@....ca>
Subject: Re: ATA device reset, shoud I be concerned?

On 08/26/2009 10:40 PM, Robert Hancock wrote:
> On 01/21/2008 08:33 AM, Tejun Heo wrote:
>> Tejun Heo wrote:
>>> IMHO, losing media error information is much better than locking up a
>>> machine hard. We can start white listing known good controllers but I'm
>>> skeptical how much benefit it will bring.
>>
>> Just a data point, even ICHs lock up after PHY event if the wrong TF
>> register is accessed. I just don't think tempting with TF regs after
>> timeout is worth the cost.
>
> Nvidia CK804 SATA controllers appear to also explode on reading TF
> registers after media errors in certain cases. (They tend to either
> lockup the machine or throw HyperTransport timeout machine check
> exceptions). I suspect those error paths aren't well tested (except that
> it even explodes in Windows with the default Microsoft IDE driver, when
> reading a scratched DVD on a SATA drive, for example.)

Well, reading TF when DMA or other operation is enabled is a big 
no-no...  according to spec.  If we are touching TF before data xfer 
operation is completed, and host controller has a chance to receive D2H 
FIS, TF is undefined (except Status, in some cases).

	Jeff




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