Messages in this thread | | | Date | Fri, 19 Sep 2008 22:01:35 +0900 | Subject | Re: [GIT PULL] AMD IOMMU updates for 2.6.28 | From | FUJITA Tomonori <> |
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On Fri, 19 Sep 2008 14:34:26 +0200 Joerg Roedel <joerg.roedel@amd.com> wrote:
> 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.
Not sure. It would make sense but maybe not.
But it's the different topic. Making a generic option that affects all the IOMMUs is an important issue for everyone. All the parties need to discuss it and agree.
> 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.
Yes, that's the point. We should not have such important change in AMD IOMMU updates.
So please just make 'fullflush' as AMD IOMMU's option.
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