On 19/01/2018 09:42, Peter Xu wrote: > I encountered an event loss problem during unplugging vfio devices: > > https://bugzilla.redhat.com/show_bug.cgi?id=1531393 > > I thought it should be a simple VT-d issue but I was wrong. The whole > debugging leads me to these patches. > > Basically I think what we missed is that when unregistering memory > listeners, we don't really call region_del() at all. Instead we just > remove ourselves from the listener list. IMHO that's not enough. A > clean unregister should undo all possible changes that have done > during region_add(). That's patch 1. > > Patch 2 fixes a vfio issue when patch 1 is applied.
It makes sense, though of course patch 1 must come second for bisectability. Of the other listeners, most do not implement region_del, but commit must be audited as well. What matters is whether the listener is unregistered, and only few are: - kvm_arm_machine_init_done must unregister the listener after the QSLIST_FOREACH_SAFE loop. - Xen seems okay - vhost needs to remove the memory_region_unref loop after unregistering the listener - and this must be done at the same time as patch 1, not before - virtio seems okay Thanks, Paolo
