Messages in this thread | | | Date | Wed, 10 Sep 2008 23:45:34 +0900 | Subject | Re: [PATCH] x86: avoid unnecessary low zone allocation in AMD IOMMU's alloc_coherent | From | FUJITA Tomonori <> |
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On Wed, 10 Sep 2008 16:38:18 +0200 Joerg Roedel <joro@8bytes.org> wrote:
> On Wed, Sep 10, 2008 at 11:24:57PM +0900, FUJITA Tomonori wrote: > > On Wed, 10 Sep 2008 15:53:47 +0200 > > Joerg Roedel <joerg.roedel@amd.com> wrote: > > > > > On Wed, Sep 10, 2008 at 10:37:45PM +0900, FUJITA Tomonori wrote: > > > > On Wed, 10 Sep 2008 15:10:32 +0200 > > > > Joerg Roedel <joerg.roedel@amd.com> wrote: > > > > > Can't we simply make the gfp hacks depend on > > > > > dma_ops->is_phys and avoid further gfp hacks in the hardware iommu > > > > > implementations? > > > > > > > > I thought about it but adding a new dma_ops->we_don't_want_gfp_flag > > > > hook doesn't make the code simpler much. Currently, we have the gfp > > > > setting hack in just one place. It's not bad. Adding such new hook > > > > means adding more lines than we can remove. > > > > > > The is_phys flas is already in place and its meaning is "the dma_ops > > > return bus addresses equal to physical addresses". This is exactly the > > > case when we need the gfp hacks. So I don't see a problem in just > > > skipping the gfp rewrite if is_phys is zero. I don't see a point in > > > adding gfp flags in dma_alloc_coherent and remove them again > > > dma_ops->alloc_coherent code. Specially in this case where we already > > > know in dma_alloc_coherent if we really need the flag rewrite. > > > > dma_ops->is_phys doesn't work well for GART and Intel IOMMU, that do > > virtual mappings for some devices and doesn't for some. > > > > We need to a hook that can pass a point to a device to IOMMUs like: > > > > dma_ops->is_phys(struct device *dev) > > > > > > Because they need to look at a device to know if they will do virtual > > mappings or not for it. > > Ok, thats a valid point. I queue your patch with the AMD IOMMU updates > for 2.6.28. Thanks.
Ingo already has queued it his tree, I think.
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