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charset="utf-8" Content-Transfer-Encoding: quoted-printable On Tue, Nov 03, 2026, Paolo Bonzini wrote: > On Mon, Nov 2, 2026 at 6:43=E2=80=AFPM Sean Christopherson wrote: > > > If so, we need to make that a thread for RT kernels if you want to ca= ll > > > kzalloc_obj(). > > > > Eww. I can't imagine there's a sane usecase for memory overcommitting = a real-time > > guest. >=20 > While I agree with the feeling, the dummy allocation path should be > mostly dead, because page fault should never (?) enable interrupts > before waiting: >=20 > #PF interrupt gate > exc_page_fault() > kvm_handle_async_pf() > __kvm_handle_async_pf() > irqentry_enter() > kvm_async_pf_task_wait_schedule() > kvm_async_pf_queue_task() <- registers waiter > prepare_to_swait_exclusive() > local_irq_enable() >=20 > The dummy allocation path is only reachable if it's an L1 hypervisor > that is getting an async page fault while L2 is running, because it > enables irq before the call to kvm_async_pf_task_wait_schedule(). I > think we can drop the dummy allocation for good, which would be even > better. +1, I completely forgot what this code is doing (although that implies I ev= er knew in the first place...). > Whether you would still want to disable APF for RT kernels is up to you. Nah, on second thought there are use cases for async #PF other than memory overcommit. Whether or not they coincide with PREEMPT_RT is debatable, but= I don't think it makes sense to go looking for trouble.