On Fri, 2017-09-08 at 14:44 +1000, Nicholas Piggin wrote: > On Fri, 08 Sep 2017 08:05:38 +1000 > Benjamin Herrenschmidt <[email protected]> wrote: > > > On Fri, 2017-09-08 at 00:51 +1000, Nicholas Piggin wrote: > > > When permissiveness is relaxed, or found to have been relaxed by > > > another thread, we flush that address out of the TLB to avoid a > > > future fault or micro-fault due to a stale TLB entry. > > > > > > Currently for processes with TLBs on other CPUs, this flush is always > > > done with a global tlbie. Although that could reduce faults on remote > > > CPUs, a broadcast operation seems to be wasteful for something that > > > can be handled in-core by the remote CPU if it comes to it. > > > > > > This is not benchmarked yet. It does seem cut some tlbie operations > > > from the bus. > > > > What happens with the nest MMU here ? > > Good question, I'm not sure. I can't tell from the UM or not if the > agent and NMMU must discard cached translations if there is a > translation cached but it has a permission fault. It's not clear > from that I've read that if it's relying on the host to send back a > tlbie.
I think it's supposed to re-do a tablewalk. > I'll keep digging. > > Thanks, > Nick
