Messages in this thread | | | Date | Fri, 19 Sep 2008 14:34:26 +0200 | From | Joerg Roedel <> | Subject | Re: [GIT PULL] AMD IOMMU updates for 2.6.28 |
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On Fri, Sep 19, 2008 at 09:24:18PM +0900, FUJITA Tomonori wrote: > On Fri, 19 Sep 2008 13:52:59 +0200 > Joerg Roedel <joerg.roedel@amd.com> wrote: > > > On Fri, Sep 19, 2008 at 08:47:54PM +0900, FUJITA Tomonori wrote: > > > On Fri, 19 Sep 2008 20:23:50 +0900 > > > FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp> wrote: > > > > > > And you don't need to add 'fullflush' to the generic place too. > > > > > > 'fullflush' will be supported with only GART and AMD IOMMU. So adding > > > the description of it to both GART and AMD IOMMU should be fine. > > > > > > 'fullflush' has the same meaning for both IOMMUs. That's nice > > > consistency, I think. > > > > Huh? The whole point of this patch was to have a common option between > > IOMMUs to disable lazy IOTLB flushing. This was suggested by _you_ and > > the only reason I wrote this patch. > > You misunderstand what I meant. I'm sorry if my explanation is not > clear. > > > > After this patch we can change other IOMMU implementations with lazy > > flushing to use that parameter too. > > I'm not sure that Calgary wants to support such option. It always uses > lazy flushing. > > > What I don't like is that there is no consistency about the option > name for lazy flushing. It doesn't mean that we move the option to the > generic place. > > Here's my first reply: > > = > Would it be nice to have consistency of IOMMU parameters? > > VT-d also has the kernel-boot option for this lazy flushing trick > though VT-d 'strict' option is more vague than 'unmap_flush' > = > > What I meant that using the option name 'strict' that VT-d uses for > lazy flushing for AMD IOMMU would be better than introducing a new > option name, "unmap_flush" for AMD IOMMU though I don't think that > 'strict' is the good name. > > > Seems 'fullflush' is better than 'strict'. So I think that it's better > to use 'fullflush' for AMD IMMU rather introducing a new name, > 'unmap_flush'. But again, it doesn't mean that 'fullflush' moves to > the generic place.
Ok, so now we have fullflush, which makes sense for all x86 hardware IOMMUs except maybe Calgary (from what I know about Calgary fullflush can be implemented there only with a abyssal performance penalty nobody is willing to pay). So it makes sense to have the option in the generic place. But we can surely add a comment that it does not affect Calgary to the kernel documentation (and change VT-d to use that parameter too). But the AMD IOMMU update chain is not the right place for making big changes to other IOMMUs.
Joerg
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