On Wed, 12 Feb 2020 13:44:53 +0100 Christian Borntraeger <borntraeger@xxxxxxxxxx> wrote: > On 12.02.20 13:39, Cornelia Huck wrote: > [...] > > >> + */ > >> + return 0; > > > > Given that this function now always returns 0, we basically get a > > completely useless roundtrip into the kernel when userspace is trying > > to setup the mappings. > > > > Can we define a new IO_ADAPTER_MAPPING_NOT_NEEDED or so capability that > > userspace can check? > > Nack. This is one system call per initial indicator ccw. This is so seldom > and cheap that I do not see a point in optimizing this. NB that zpci also calls this. Probably a rare event there as well. > > > > This change in behaviour probably wants a change in the documentation > > as well. > > Yep.
