Re: [PATCH 2/2] arm64: efi: Pass reboot cmd parameter to efi_reboot()

[Sumit Garg <sumit.garg@kernel.org>]

On Fri, Nov 14, 2025 at 10:26:03AM +0100, Ard Biesheuvel wrote:
> On Fri, 14 Nov 2025 at 09:51, Sumit Garg <sumit.garg@kernel.org> wrote:
> >
> > From: Sumit Garg <sumit.garg@oss.qualcomm.com>
> >
> > EFI ResetSystem runtime service allows for platform specific reset type
> > allowing the OS to pass reset data for the UEFI implementation to take
> > corresponding action. So lets pass the reboot cmd parameter for the EFI
> > driver to determine whether it's a platform specific reset requested or
> > not.
> >
> > Signed-off-by: Sumit Garg <sumit.garg@oss.qualcomm.com>
> > ---
> >  arch/arm64/kernel/process.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c
> > index fba7ca102a8c..51784986c568 100644
> > --- a/arch/arm64/kernel/process.c
> > +++ b/arch/arm64/kernel/process.c
> > @@ -136,7 +136,7 @@ void machine_restart(char *cmd)
> >          * ResetSystem().
> >          */
> >         if (efi_enabled(EFI_RUNTIME_SERVICES))
> > -               efi_reboot(reboot_mode, NULL);
> > +               efi_reboot(reboot_mode, cmd);
> >
> 
> I agree with the general principle. However, there are already
> existing callers of kernel_restart() that would end up passing a
> random string to efi_reboot(), resulting in platform specific reset
> with undefined result.

Yeah true but the UEFI spec says:

"If the platform does not recognize the EFI_GUID in ResetData the platform
must pick a supported reset type to perform. The platform may optionally
log the parameters from any non-normal reset that occurs."

So, in these cases the UEFI implementation can fallback to normal reset
optionally logging the reset data being passed. Does that sounds
reasonable to you?

-Sumit

> 
> E.g.,
> 
> $ git grep kernel_restart\(\"
> drivers/md/dm-verity-target.c:          kernel_restart("dm-verity
> device corrupted");
> drivers/md/dm-verity-target.c:  kernel_restart("dm-verity device has
> I/O error");
> drivers/memory/emif.c:                  kernel_restart("SDRAM
> Over-temp Emergency restart");
> 
> 
> >         /* Now call the architecture specific reboot code. */
> >         do_kernel_restart(cmd);
> > --
> > 2.48.1
> >