linux-kernel - Re: UEFI EBS() failures on Lenovo T14s

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Message-ID: <CAMj1kXF0Mmr5CyyeKXO6-Ot+5cfSV6t2jPmn+TGVyjUsoYwGtw@mail.gmail.com>
Date: Thu, 28 Nov 2024 16:21:09 +0100
From: Ard Biesheuvel <ardb@...nel.org>
To: Johan Hovold <johan@...nel.org>
Cc: Leif Lindholm <leif.lindholm@....qualcomm.com>, Bjorn Andersson <andersson@...nel.org>, 
	Ricardo Salveti <ricardo@...ndries.io>, Marc Zyngier <maz@...nel.org>, linux-efi@...r.kernel.org, 
	linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: UEFI EBS() failures on Lenovo T14s

On Thu, 28 Nov 2024 at 15:46, Johan Hovold <johan@...nel.org> wrote:
>
> On Thu, Nov 28, 2024 at 12:05:09PM +0100, Ard Biesheuvel wrote:
>
> > If you're happy to experiment more, you could try and register a
> > notification for EFI_EVENT_GROUP_BEFORE_EXIT_BOOT_SERVICES using
> > CreateEventEx(), and see if it gets called when ExitBootServices() is
> > called. That would at least help narrow it down.
>
> Thanks for the suggestion.
>
> I see the notify function being called when I signal it as well as on
> each ExitBootServices().
>

Interesting. That means the EDK2 fork is fairly recent.

FYI https://github.com/tianocore/edk2/pull/6481


> With an efi_printk() in the callback ExitBootServices() fails as
> expected, but with an empty function the kernel seems to start every
> time.
>
> Interestingly, ExitBootServices() now succeeds also if I add back the
> CloseEvent() call. In fact, it works also if I never signal the event
> (i.e. if I just create and close the event).
>

Is it still invoked by the firmware if you closed the event before EBS()?

> The patch below should suffice as a workaround I can carry until the
> firmware has been fixed.
>

Ok. I'd prefer to get this fixed on the firmware side as well.