Re: [PATCH] efi: add dynamic control interface for EFI runtime services

[Ilias Apalodimas]

On Thu, 3 Sept 2026 at 13:08, Ard Biesheuvel <ardb@xxxxxxxxxx> wrote:
>
>
> On Sat, 15 Aug 2026, at 11:50, Junxiao Chang wrote:
> > Add an interface for PREEMPT_RT kernels to dynamically enable or
> > disable EFI runtime services.
> >
> > EFI runtime services are typically disabled on RT systems using
> > kernel parameters such as "noefi" or "efi=disable" to avoid
> > long latency caused by firmware calls. However, this permanently
> > disables EFI runtime services, preventing operations such as UEFI
> > firmware updates.
> >
> > With this change, EFI runtime services can be disabled while
> > real-time workloads are running and re-enabled afterwards,
> > providing low-latency operation without permanently sacrificing
> > firmware functionality.
> >
> > Signed-off-by: Junxiao Chang <junxiao.chang@xxxxxxxxx>
> > ---
> >  drivers/firmware/efi/efi.c              | 31 +++++++++++++++++++++++++
> >  drivers/firmware/efi/runtime-wrappers.c | 28 ++++++++++++++++++++++
> >  include/linux/efi.h                     |  1 +
> >  3 files changed, 60 insertions(+)
> >
>
> I've queued this up now - thanks.

Apologies for the noise, resending as the previous one was dropped.
One of the things that changes with runtime services is mounting the
efivarfs as RO/RW.
I am pretty sure nothing bad will happen, but is it worth the pain of
remounting it on enable/disable?

Thanks
/Ilias