>> What if you detach and re-attach? >> Is it fast then? >> If yes this means the issue is COW breaking that occurs with >> get_user_pages, not translation as such. >> Try hugepages with prealloc - does it help? > >I agree it's either COW breaking or (similarly) locking pages that the guest >hasn't touched yet. > >You can use prealloc or "-rt mlock=on" to avoid this problem. > It gets better if using "-rt mlock=on", but still cannot resolve the problem completely. VT-d and EPT do not share the GPA->HPA page-table, still need to build VT-d GPA->HPA DMAR page-table, Although the "-rt mlock=on" option guarantees that all of vm memory have been touched before attaching the pass-through device, the building is faster, but which still need some time.
Thanks, Zhang Haoyu >Paolo
