Messages in this thread | | | Date | Tue, 16 Sep 2008 18:20:29 +0200 | From | Andi Kleen <> | Subject | Re: [PATCH 0/3] fix GART to respect device's dma_mask about virtual mappings |
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On Tue, Sep 16, 2008 at 05:52:11PM +0200, Joerg Roedel wrote: > On Tue, Sep 16, 2008 at 10:20:40PM +0900, FUJITA Tomonori wrote: > > On Tue, 16 Sep 2008 02:54:32 +0200 > > Andi Kleen <andi@firstfloor.org> wrote: > > > > > FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp> writes: > > > > > > > Currently, gart IOMMU ignores device's dma_mask when it does virtual > > > > mappings. So it could give a device a virtual address that the device > > > > can't access to. > > > > > > Huh? That is what the need_iommu() logic in gart_map_sg() > > > does. An I'm not aware of any bugs in this area. > > > > What the need_iommu() does is seeing if GART needs to do virtual > > mappings or not. > > > > (After need_iommu() checking) What this patchset does is to guarantee > > that GART provides a virtual address that a device can access to. > > > > > > > Did you actually see that failure in practice? I don't see > > > how it could happen. > > > > No, I did not. This patchset does the right thing theoretically, I > > think, but if such problem never happens for GART, I'll drop the patch > > for GART. Joerg? > > I am not aware of any failures which are fixed by these patches.
AFAIK all subsystems deal with it on their own. That is because i386 is the same (no remapping pci_map_* at all) and subsystems are usually written to i386 semantics.
> But in > theory there could be failures.
They will stay failures because GFP_DMA bouncing can not be really done today in the pci_map_* layer. With a lot of effort you could probably fix all that, but I doubt it would be worth the effort for the few devices left with DMA masks < 32bit.
-Andi
> > Joerg > > -- > | AMD Saxony Limited Liability Company & Co. KG > Operating | Wilschdorfer Landstr. 101, 01109 Dresden, Germany > System | Register Court Dresden: HRA 4896 > Research | General Partner authorized to represent: > Center | AMD Saxony LLC (Wilmington, Delaware, US) > | General Manager of AMD Saxony LLC: Dr. Hans-R. Deppe, Thomas McCoy >
-- ak@linux.intel.com
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