Le 19/12/2023 à 07:33, Michael Ellerman a écrit : > Aneesh Kumar K.V <aneesh.ku...@kernel.org> writes: >> Luming Yu <luming...@shingroup.cn> writes: >> >>> Before we have powerpc to use the generic entry infrastructure, >>> the call to fire user return notifier is made temporarily in powerpc >>> entry code. >>> >> >> It is still not clear what will be registered as user return notifier. >> Can you summarize that here? > > fire_user_return_notifiers() is defined in kernel/user-return-notifier.c > > That's built when CONFIG_USER_RETURN_NOTIFIER=y. > > That is not user selectable, it's only enabled by: > > arch/x86/kvm/Kconfig: select USER_RETURN_NOTIFIER > > So it looks to me like (currently) it's always a nop and does nothing. > > Which makes me wonder what the point of wiring this feature up is :) > Maybe it's needed for some other feature I don't know about? > > Arguably we could just enable it because we can, and it currently does > nothing so it's unlikely to break anything. But that also makes it > impossible to test the implementation is correct, and runs the risk that > one day in the future when it does get enabled only then do we discover > it doesn't work.
Opened an "issue" for the day we need it: https://github.com/KSPP/linux/issues/348
