On Thu, 1 Sep 2016 11:58:48 +0800 Peter Xu <pet...@redhat.com> wrote:
> On Wed, Aug 31, 2016 at 08:43:42PM -0600, Alex Williamson wrote: > > > > >>This reverts commit 3cb3b1549f5401dc3a5e1d073e34063dc274136f. Vhost > > > > >>device IOTLB API will get notified and send invalidation request to > > > > >>vhost through this notifier. > > > > >AFAICT this series does not address the original problem for which > > > > >commit 3cb3b1549f54 was added. We've only addressed the very narrow > > > > >use case of a device iotlb firing the iommu notifier therefore this > > > > >change is a regression versus 2.7 since it allows invalid > > > > >configurations with a physical iommu which will never receive the > > > > >necessary notifies from intel-iommu emulation to work properly. > > > > >Thanks, > > > > > > > > > >Alex > > > > > > > > Looking at vfio, it cares about map but vhost only cares about IOTLB > > > > invalidation. Then I think we probably need another kind of notifier in > > > > this > > > > case to avoid this. > > > > > > Shall we leverage IOMMUTLBEntry.perm == IOMMU_NONE as a sign for > > > invalidation? If so, we can use the same IOTLB interface as before. > > > IMHO these two interfaces are not conflicting? > > > > > > Alex, > > > > > > Do you mean we should still disallow user from passing through devices > > > while Intel IOMMU enabled? If so, not sure whether patch below can > > > solve the issue. > > > > > > It seems that we need a "name" for either IOMMU notifier > > > provider/consumer, and we should not allow (provider==Intel && > > > consumer==VFIO) happen. In the following case, I added a name for > > > provider, and VFIO checks it. > > > > Absolutely not, intel-iommu emulation is simply incomplete, the IOMMU > > notifier is never called for mappings. There's a whole aspect of > > iommu notifiers that intel-iommu simply hasn't bothered to implement. > > Don't punish vfio for actually making use of the interface as it was > > intended to be used. AFAICT you're implementing the unmap/invalidation > > half, without the actual mapping half of the interface. It's broken > > and incompatible with any iommu notifiers that expect to see both > > sides. Thanks, > > Yeah I think I got your point. Thanks for the explanation. > > Now I agree with Jason that we may need another notifier mechanism. What!? I see no reason you need a different notifier, just fix the implementation of the current one. As a bonus this will also give you working VFIO passthrough with vIOMMU on x86, something which should work already, but doesn't. -- David Gibson <dgib...@redhat.com> Senior Software Engineer, Virtualization, Red Hat
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