On Wed, 5 Mar 2025 12:15:35 +0000 Mark Rutland <mark.rutland@xxxxxxx> wrote: > On Wed, Mar 05, 2025 at 11:49:25AM +0100, Valentin Schneider wrote: > > From: Mark Rutland <mark.rutland@xxxxxxx> > > > > For an architecture to enable CONFIG_ARCH_HAS_RESCHED_LAZY, two things are > > required: > > 1) Adding a TIF_NEED_RESCHED_LAZY flag definition > > 2) Checking for TIF_NEED_RESCHED_LAZY in the appropriate locations > > > > 2) is handled in a generic manner by CONFIG_GENERIC_ENTRY, which isn't > > (yet) implemented for arm64. However, outside of core scheduler code, > > TIF_NEED_RESCHED_LAZY only needs to be checked on a kernel exit, meaning: > > o return/entry to userspace. > > o return/entry to guest. > > > > The return/entry to a guest is all handled by xfer_to_guest_mode_handle_work() > > which already does the right thing, so it can be left as-is. > > > > arm64 doesn't use common entry's exit_to_user_mode_prepare(), so update its > > return to user path to check for TIF_NEED_RESCHED_LAZY and call into > > schedule() accordingly. > > > > Link: https://lore.kernel.org/linux-rt-users/20241216190451.1c61977c@xxxxxxxxxxxxxxxxxxxx/ > > Link: https://lore.kernel.org/all/xhsmh4j0fl0p3.mognet@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/ > > Signed-off-by: Mark Rutland <mark.rutland@xxxxxxx> > > [testdrive, _TIF_WORK_MASK fixlet and changelog.] > > Signed-off-by: Mike Galbraith <efault@xxxxxx> > > [Another round of testing; changelog faff] > > Signed-off-by: Valentin Schneider <vschneid@xxxxxxxxxx> > > --- > > arch/arm64/Kconfig | 1 + > > arch/arm64/include/asm/thread_info.h | 16 +++++++++------- > > arch/arm64/kernel/entry-common.c | 2 +- > > 3 files changed, 11 insertions(+), 8 deletions(-) > > Catalin, Will, given this is small and self-contained, I reckon it makes > sense to pick this up ahead of Jinjie's series to move arm64 over to the > generic entry library (which is on my queue of things to review). Even > if we pick up both, it'll be easier to bisect and debug issues caused by > this patch alone. > > The fixes/cleanups from Mike and Valentin look right to me, so FWIW: > > Acked-by: Mark Rutland <mark.rutland@xxxxxxx> Thank you, all. Much appreciated. Petr T
