[PATCH v6 03/11] KVM: arm64: Relax locking for kvm_test_age_gfn and kvm_age_gfn

[David Matlack]

On Thu, Aug 29, 2024 at 5:48 PM Oliver Upton <oliver.upton at linux.dev> wrote:
>
> On Thu, Aug 29, 2024 at 05:33:00PM -0700, James Houghton wrote:
> > On Mon, Aug 19, 2024 at 1:42 PM Oliver Upton <oliver.upton at linux.dev> wrote:
> > > Asking since you had a setup / data earlier on when you were carrying
> > > the series. Hopefully with supportive data we can get arm64 to opt-in
> > > to HAVE_KVM_MMU_NOTIFIER_YOUNG_FAST_ONLY as well.
> >
> > I'll keep trying some other approaches I can take for getting similar
> > testing that Yu had; it is somewhat difficult for me to reproduce
> > those tests (and it really shouldn't be.... sorry).
>
> No need to apologize. Getting good test hardware for arm64 is a complete
> chore. Sure would love a functional workstation with cores from this
> decade...
>
> > I think it makes most sense for me to drop the arm64 patch for now and
> > re-propose it (or something stronger) alongside enabling aging. Does
> > that sound ok?
>
> I'm a bit disappointed that we haven't gotten forward progress on the
> arm64 patches, but I also recognize this is the direction of travel as
> the x86 patches are shaping up.
>
> So yeah, I'm OK with it, but I'd love to get the arm64 side sorted out
> soon while the context is still fresh.

Converting the aging notifiers to holding mmu_lock for read seems like
a pure win and minimal churn. Can we keep that patch in v7 (which
depends on the lockless notifier refactor, i.e. is not completely
stand-alone)? We can revisit enabling MGLRU on arm64 in a subsequent
series.
>
> --
> Thanks,
> Oliver