On Wed, 24 Oct 2007 07:40:50 -0400
Jeff Garzik <jeff@garzik.org> wrote:

quoted text
> FUJITA Tomonori wrote:
> > IOMMUs merges scatter/gather segments without considering a low level
> > driver's restrictions. The problem is that IOMMUs can't access to the
> > limitations because they are in request_queue.
> > 
> > This patchset introduces a new structure, device_dma_parameters,
> > including dma information. A pointer to device_dma_parameters is added
> > to struct device. The bus specific structures (like pci_dev) includes
> > device_dma_parameters. Low level drivers can use dma_set_max_seg_size
> > to tell IOMMUs about the restrictions.
> > 
> > We can move more dma stuff in struct device (like dma_mask) to struct
> > device_dma_parameters later (needs some cleanups before that).
> > 
> > This includes patches for all the IOMMUs that could merge sg (x86_64,
> > ppc, IA64, alpha, sparc64, and parisc) though only the ppc patch was
> > tested. The patches for other IOMMUs are only compile tested.
> > 
> > Thanks to everyone for the comments on the previous submission
> > to linux-scsi.
> > 
> > This is against 2.6.24-rc1. The same patchset is also available:
> > 
> > git://git.kernel.org/pub/scm/linux/kernel/git/tomo/linux-2.6-misc.git iommu-sg-fixes
> 
> Are you interested in collecting patches to libata that eliminate the 
> hand-rolled S/G splitting?  e.g. now ata_fill_sg() and mv_fill_sg() can 
> be made much more efficient.

Yeah, but ATA has the segment boundary limit too. It's much more
tricky than the segment size limit. It makes the IOMMU free space
managemet complicated.


quoted text
> Again, thanks for doing this!  It's been needed for a long time.

My pleasure.
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