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SubjectRe: [00/15] swiotlb cleanup
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On Mon, 13 Jul 2009 13:20:22 +0900
FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp> wrote:

> On Fri, 10 Jul 2009 16:12:48 +0200
> Ingo Molnar <mingo@elte.hu> wrote:
>
> > > functionality and reimplemented the surrounding infrastructure in
> > > terms of that (and incorporating our additional requirements). I
> > > prototyped this (it is currently unworking, in fact it seems to
> > > have developed rather a taste for filesystems :-() but the
> > > diffstat of my WIP patch is:
> > >
> > > arch/x86/kernel/pci-swiotlb.c | 6
> > > arch/x86/xen/pci-swiotlb.c | 2
> > > drivers/pci/xen-iommu.c | 385 ++++++++++++++++++++++++++++++++++++++++--
> > > include/linux/swiotlb.h | 12 +
> > > lib/swiotlb.c | 10 -
> > > 5 files changed, 385 insertions(+), 30 deletions(-)
> > >
> > > where a fair number of the lines in xen-iommu.c are copies of
> > > functions from swiotlb.c with minor modifications. As I say it
> > > doesn't work yet but I think it's roughly indicative of what such
> > > an approach would look like. I don't like it much but am happy to
> > > run with it if it looks to be the most acceptable approach. [...]
> >
> > +400 lines of code to avoid much fewer lines of generic code impact
> > on the lib/swiotlb.c side sounds like a bad technical choice to me.
>
> The amount of code is not the point. The way to impact on the
> lib/swiotlb.c is totally wrong from the perspective of the kernel
> design; it uses architecture code in the very original (xen) way.

btw, '+400 lines of code to avoid much fewer lines of generic code
impact on the lib/swiotlb.c' doesn't sound true to me.

Here is a patch in the way that Xen people want to do:

http://patchwork.kernel.org/patch/26343/

---
arch/x86/Kconfig | 4 +
arch/x86/include/asm/io.h | 2 +
arch/x86/include/asm/pci_x86.h | 1 +
arch/x86/include/asm/xen/iommu.h | 12 ++
arch/x86/kernel/pci-dma.c | 3 +
arch/x86/pci/Makefile | 1 +
arch/x86/pci/init.c | 6 +
arch/x86/pci/xen.c | 51 +++++++
drivers/pci/Makefile | 2 +
drivers/pci/xen-iommu.c | 271 ++++++++++++++++++++++++++++++++++++++

Even with the way that Xen people want to do, drivers/pci/xen-iommu.c
is about 300 lines. And my patchset removes the nice amount of lines
for dom0 support. I don't see much difference wrt lines.


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