linux-kernel - Re: [PATCH -mm 0/11] fix iommu sg merging problem

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Message-ID: <471F2F42.1080806@garzik.org>
Date:	Wed, 24 Oct 2007 07:40:50 -0400
From:	Jeff Garzik <jeff@...zik.org>
To:	FUJITA Tomonori <tomof@....org>
CC:	akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
	linux-scsi@...r.kernel.org, James.Bottomley@...elEye.com,
	jens.axboe@...cle.com, greg@...ah.com, muli@...ibm.com,
	paulus@...ba.org, tony.luck@...el.com, davem@...emloft.net,
	kyle@...isc-linux.org, aacraid@...ptec.com,
	fujita.tomonori@....ntt.co.jp
Subject: Re: [PATCH -mm 0/11] fix iommu sg merging problem

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.

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

	Jeff



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