On Fri, Oct 21, 2016 at 11:50:05AM +1100, David Gibson wrote: [...]
> > > In my setup the VFIO registered two memory areas with one page of > > > unregistered memory > > > between them. > > > > > > When I'm calling memory_region_notify_iommu it calls the notifier function > > > of VFIO twice > > > when the second time is failing with warning to console as the new mapping > > > is already present. > > > > > > The notifier function of VFIO should ignore IOMMUTLBEntry that is not in > > > the correct > > > range. > > > > Hmm, right vfio_listener_region_add() is called for a > > MemoryRegionSection, but then we add an iommu notifier to the > > MemoryRegion, so we end up with a notifier per MemoryRegionSection > > regardless of whether they're backed by the same MemoryRegion. Seems > > like we need a MemoryRegion based list of VFIOGuestIOMMUs so we only > > register once per MemoryRegion and then sort though the list of > > VFIOGuestIOMMUs for a given MemoryRegion to find the one affected. > > David, does that sound right to you? I think we already have such a list (VFIOContainer.giommu_list)? Can we use that to do it? When we try to add a new IOMMU notifier for specific MemoryRegion, we can first traverse VFIOContainer.giommu_list and see whether there are existing MemoryRegion registered, and we only register if it's the first one. > > Well, I think that would work. But I think it would be better to fix > it from the other side: > > We add the range to be notified into the IOMMUNotifier structure and > filter based on that range in memory_region_notify_iommu. > > It means a little more list searching and filtering on notify, but it > avoids having to have another list and search on the VFIO side. I > think it will also better deal with cases where part of an IOMMU > mapped region is inaccessible due to an intermediate bridge. IIUC, this will still need to keep several VFIOGuestIOMMUs which contains exactly the same content? Thanks, -- peterx