Re: WARNING: at drivers/ata/libata-core.c:5988 ata_qc_issue()

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James Bottomley wrote:
On Thu, 2008-01-24 at 23:29 -0500, Mark Lord wrote:
Tejun Heo wrote:
Mark Lord wrote:
..
Super!  You've done a great job with this stuff, Tejun!
Thanks but I can't really say nice things about how sata_sil24's
qc_defer() is implemented or how we generally handle command deferring.
 We really need the control at the higher level - request_queue group.
Oh well... I guess you guys will be talking about it over beer again
soon.  :-)
..

You too?

Another one for those beers, is a way to tell the IOMMU code about
physical segment limitations -- so we can stop having to allocate
PRD tables 2X as big as necessary in drivers like sata_mv.

If the IOMMU would observe the queue dma_boundary parameter, is that
enough?  (it is for the 64k PRD limit).  If so, there are already
patches in the works to solve this permanently.  If not, could we get
the requirements to see how it might be done?
..

That sounds like the right thing.

We just have ensure that:

1. single SG/PRD entries never cross a 64KB address boundary.

and these two then naturally follow for free:

2. single SG/PRD entries never exceed 64KB.
3. single SG/PRD entries never cross a 32-bit address boundary.

Are the patches going into 2.6.25 ?
How do we take advantage of them ?

Cheers

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