Re: [PATCH] firmware: efi: add a separate timeout for UpdateCapsule()

[Yeoreum Yun <yeoreum.yun@arm.com>]

Hi Ard,

> Hello Yeoreum Yun,
> 
> On Thu, 3 Sep 2026, at 13:32, Yeoreum Yun wrote:
> > On platforms that allows to update firmware in runtime, UpdateCapsule()
> > may immediately write a firmware image to persistent storage.
> > This operation can take longer than EFI_RTS_TIMEOUT.
> >
> > Use a separate timeout for the UpdateCapsule() runtime service. By
> > default, wait indefinitely to avoid interrupting an ongoing firmware
> > update. Administrators may configure an appropriate timeout, in seconds,
> > through /sys/firmware/efi/capsule_update_timeout.
> >
> > Signed-off-by: Yeoreum Yun <yeoreum.yun@arm.com>
> > ---
> >  drivers/firmware/efi/efi.c              | 41 +++++++++++++++++++++++++
> >  drivers/firmware/efi/runtime-wrappers.c | 14 +++------
> >  include/linux/efi.h                     | 10 ++++++
> >  3 files changed, 55 insertions(+), 10 deletions(-)
> >
> 
> Given that UpdateCapsule() is rarely used these days at runtime, I
> wonder if we should just call it synchronously instead of via the
> EFI workqueue.
> 
> I assume that would also solve the timeout issue?

Might be. But it would make *non-preemptible* for UpdateCapsule().
AFAIK the purpose of running runtime service with efi_queue to
run it in indepdent context and to be preemtible in case of arm64.

Since most of UpdateCapsule() will be called via capsule-loader's misc
device, if UpdateCaspule() is called synchronously, It would be
non-preemtible in arm64 platform.

But, some platform could be preemptible while updating firmware so
I think it would be better that it would be called via EFI workqueue.

[...]

Thanks!

-- 
Sincerely,
Yeoreum Yun