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From: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
To: mingo@elte.hu
Cc: jeremy@goop.org, tony.luck@intel.com, linux-ia64@vger.kernel.org,
	Ian.Campbell@citrix.com, x86@kernel.org,
	linux-kernel@vger.kernel.org, fujita.tomonori@lab.ntt.co.jp,
	linuxppc-dev@ozlabs.org, joerg.roedel@amd.com
Subject: Re: [00/15] swiotlb cleanup
Date: Fri, 10 Jul 2009 14:35:10 +0900	[thread overview]
Message-ID: <20090710143408A.fujita.tomonori@lab.ntt.co.jp> (raw)
In-Reply-To: <20090710051236.GA22218@elte.hu>

On Fri, 10 Jul 2009 07:12:36 +0200
Ingo Molnar <mingo@elte.hu> wrote:

> 
> * FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp> wrote:
> 
> > - removes unused (and unnecessary) hooks in swiotlb.
> > 
> > - adds dma_capable() and converts swiotlb to use it. It can be used to
> > know if a memory area is dma capable or not. I added
> > is_buffer_dma_capable() for the same purpose long ago but it turned
> > out that the function doesn't work on POWERPC.
> > 
> > This can be applied cleanly to linux-next, -mm, and mainline. This
> > patchset touches multiple architectures (ia64, powerpc, x86) so I
> > guess that -mm is appropriate for this patchset (I don't care much
> > what tree would merge this though).
> > 
> > This is tested on x86 but only compile tested on POWERPC and IA64.
> > 
> > Thanks,
> > 
> > =
> >  arch/ia64/include/asm/dma-mapping.h    |   18 ++++++
> >  arch/powerpc/include/asm/dma-mapping.h |   23 +++++++
> >  arch/powerpc/kernel/dma-swiotlb.c      |   48 +---------------
> >  arch/x86/include/asm/dma-mapping.h     |   18 ++++++
> >  arch/x86/kernel/pci-dma.c              |    2 +-
> >  arch/x86/kernel/pci-gart_64.c          |    5 +-
> >  arch/x86/kernel/pci-nommu.c            |    2 +-
> >  arch/x86/kernel/pci-swiotlb.c          |   25 --------
> >  include/linux/dma-mapping.h            |    5 --
> >  include/linux/swiotlb.h                |   11 ----
> >  lib/swiotlb.c                          |  102 +++++++++-----------------------
> >  11 files changed, 92 insertions(+), 167 deletions(-)
> 
> Hm, the functions and facilities you remove here were added as part 
> of preparatory patches for Xen guest support. You were aware of 
> them, you were involved in discussions about those aspects with Ian 
> and Jeremy but still you chose not to Cc: either of them and you 
> failed to address that aspect in the changelogs.
> 
> I'd like the Xen code to become cleaner more than anyone else here i 
> guess, but patch submission methods like this are not really 
> helpful. A far better method is to be open about such disagreements, 
> to declare them, to Cc: everyone who disagrees, and to line out the 
> arguments in the changelogs as well - instead of just curtly 
> declaring those APIs 'unused' and failing to Cc: involved parties.
> 
> Alas, on the technical level the cleanups themselves look mostly 
> fine to me. Ian, Jeremy, the changes will alter Xen's use of 
> swiotlb, but can the Xen side still live with these new methods - in 
> particular is dma_capable() sufficient as a mechanism and can the 
> Xen side filter out DMA allocations to make them physically 
> continuous?

dma_capable() doesn't work for Xen in the way that Ian hopes.

As I said to him again and again, he tries to use arch code in the
very original way, and it's unacceptable (of course, he disagreed with
it).

I don't think that we need to take account of dom0 support; we don't
have a clear idea about an acceptable dom0 design (it needs to use
swiotlb code? I don't know yet), we don't even know we will have dom0
support in mainline. That's why I didn't CC this patchset to Xen
camp.

I think that it's more reasonable to think about how the code can
works for dom0 support when Xen people come with the new dom0 code.


> Ben, Tony, Becky, any objections wrt. the PowerPC / IA64 impact? If 
> everyone agrees i can apply them to the IOMMU tree, test it and push 
> it out to -next, etc.
> 
> 	Ingo
> --
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  reply	other threads:[~2009-07-10  5:36 UTC|newest]

Thread overview: 33+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2009-07-10  1:04 [00/15] swiotlb cleanup FUJITA Tomonori
2009-07-10  1:04 ` [PATCH 01/15] swiotlb: remove unused swiotlb_alloc_boot() FUJITA Tomonori
2009-07-10  1:04 ` [PATCH 02/15] swiotlb: remove unused swiotlb_alloc() FUJITA Tomonori
2009-07-10  1:04 ` [PATCH 03/15] swiotlb: remove swiotlb_arch_range_needs_mapping FUJITA Tomonori
2009-07-10  1:04 ` [PATCH 04/15] swiotlb: remove unnecessary swiotlb_bus_to_virt FUJITA Tomonori
2009-07-14  2:17   ` Becky Bruce
2009-07-14  5:08     ` FUJITA Tomonori
2009-07-16  3:40     ` Benjamin Herrenschmidt
2009-07-10  1:04 ` [PATCH 05/15] x86: add dma_capable() to replace is_buffer_dma_capable() FUJITA Tomonori
2009-07-10  1:04 ` [PATCH 06/15] x86: replace is_buffer_dma_capable() with dma_capable FUJITA Tomonori
2009-07-10  1:04 ` [PATCH 07/15] ia64: add dma_capable() to replace is_buffer_dma_capable() FUJITA Tomonori
2009-07-10  1:04 ` [PATCH 08/15] powerpc: " FUJITA Tomonori
2009-07-10  1:04 ` [PATCH 09/15] swiotlb: use dma_capable() FUJITA Tomonori
2009-07-10  1:04 ` [PATCH 10/15] powerpc: remove unncesary swiotlb_arch_address_needs_mapping FUJITA Tomonori
2009-07-10  1:05 ` [PATCH 11/15] remove is_buffer_dma_capable() FUJITA Tomonori
2009-07-10  1:05 ` [PATCH 12/15] x86, IA64, powerpc: add phys_to_dma() and dma_to_phys() FUJITA Tomonori
2009-07-10  1:05 ` [PATCH 13/15] swiotlb: use phys_to_dma and dma_to_phys FUJITA Tomonori
2009-07-10  1:05 ` [PATCH 14/15] powerpc: remove unused swiotlb_phys_to_bus() and swiotlb_bus_to_phys() FUJITA Tomonori
2009-07-10  1:05 ` [PATCH 15/15] x86: " FUJITA Tomonori
2009-07-10  5:12 ` [00/15] swiotlb cleanup Ingo Molnar
2009-07-10  5:35   ` FUJITA Tomonori [this message]
2009-07-10 14:02     ` Ian Campbell
2009-07-13  4:20       ` FUJITA Tomonori
2009-07-13  9:40         ` Ian Campbell
2009-07-13  9:53           ` FUJITA Tomonori
2009-07-13 10:05             ` Ian Campbell
2009-07-10 14:01   ` Ian Campbell
2009-07-10 14:12     ` Ingo Molnar
2009-07-13  4:20       ` FUJITA Tomonori
2009-07-13  9:16         ` FUJITA Tomonori
2009-07-18 10:41           ` Ingo Molnar
2009-07-14  3:13   ` Becky Bruce
2009-07-15 20:24     ` Becky Bruce

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