Re: 2.6.24-rc & SB600 AHCI no go on >=4GB of RAM

[Andi Kleen <ak@suse.de>]

On Wednesday 14 November 2007 12:55, Srihari Vijayaraghavan wrote:
> [Sorry to reply to my own email thread]
>
> Srihari Vijayaraghavan <sriharivijayaraghavan@yahoo.com.au> wrote:
> ...
>
> > No problems. Here's the log of unworking kernel with IOMMU turned on.
> > Basically it goes on reseting the SATA ports throwing many errors (none
> > are present in 2.6.23 or on 2.6.24-rc with mem=3500M) for many minutes at
> > which point I do a power reset :-(.
> >
> > Also the log of the working kernel with IOMMU but with mem=3500M is also
> > attached for the record. It's basically the same above kernel just with
> > the added parameter.
>
> Gentlemen,
>
> This changeset has introduced a regression in 2.6.24-rc, such that my
> machine boots no more:

Hmm, you got an AHCI controller that does not do 64bit DMA masks?
Or do you have CONFIG_IOMMU_DEBUG enabled? 

Anyways, not being able to deal with merged SG lists must be some
driver or hardware bug. I would stick some printks into gart_map_sg()
and try to find out where the failing DMA is initiatiated and then
split it into multiple IO submissions at the caller level.

-Andi