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. -- peterx
