linux-kernel - Re: [PATCH] efi: bump efistub version from 1.1 to 3.0 for VZLinuxBootLoader compatibility

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Date:   Mon, 29 May 2023 09:51:08 +0900
From:   Akihiro Suda <suda.kyoto@...il.com>
To:     Ard Biesheuvel <ardb@...nel.org>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-efi@...r.kernel.org, Linux x86 <x86@...nel.org>
Subject: Re: [PATCH] efi: bump efistub version from 1.1 to 3.0 for
 VZLinuxBootLoader compatibility

> > The next version will be 7 (0b111).
>
> How so? If this is going to be a monotonically increasing sequence
> after all, it is still not a bit mask, and this change defeats the
> purpose.

Sorry, I forgot to append ", if it will retain compatibility with 0b11".

> I'll queue this as a fix, but I'm going to tweak the comment (and the
> commit log) a bit, if you don't mind

Thanks, please feel free to tweak that.

> I'd appreciate it if you still report this as a bug with Apple, though.

Reported via https://www.apple.com/feedback/macos.html


2023年5月29日(月) 3:48 Ard Biesheuvel <ardb@...nel.org>:
>
> On Sun, 28 May 2023 at 09:59, Akihiro Suda <suda.kyoto@...il.com> wrote:
> >
> > - LINUX_EFISTUB_MAJOR_VERSION is bumped from 1 (0b1) to 3 (0b11).
> >   The value is now a bitfield.
> >
>
> OK
>
> > The next version will be 7 (0b111).
>
> How so? If this is going to be a monotonically increasing sequence
> after all, it is still not a bit mask, and this change defeats the
> purpose.
>
> > - LINUX_EFISTUB_MINOR_VERSION is pinned to 0x0, because Apple's
> >   VZLinuxBootLoader [1] cannot boot a kernel with other minor version value [2],
> >   even though it does not use UEFI. Tested with macOS 13.4 (x86_64).
> >
> > [1] https://developer.apple.com/documentation/virtualization/vzlinuxbootloader
> > [2] https://lore.kernel.org/linux-efi/CAG8fp8Teu4G9JuenQrqGndFt2Gy+V4YgJ=hN1xX7AD940YKf3A@mail.gmail.com/
> >
> > Closes: https://bugzilla.kernel.org/show_bug.cgi?id=217485
> > Signed-off-by: Akihiro Suda <akihiro.suda.cz@....ntt.co.jp>
>
> I'll queue this as a fix, but I'm going to tweak the comment (and the
> commit log) a bit, if you don't mind
>
> I'd appreciate it if you still report this as a bug with Apple, though.
>
> Thanks,
> Ard.
>
> > ---
> >  include/linux/pe.h | 20 ++++++++++++++++++--
> >  1 file changed, 18 insertions(+), 2 deletions(-)
> >
> > diff --git a/include/linux/pe.h b/include/linux/pe.h
> > index 5e1e11540870..ee5ade19b7eb 100644
> > --- a/include/linux/pe.h
> > +++ b/include/linux/pe.h
> > @@ -27,9 +27,25 @@
> >   * On x86, LoadImage() and StartImage() can be omitted if the EFI handover
> >   * protocol is implemented, which can be inferred from the version,
> >   * handover_offset and xloadflags fields in the bootparams structure.
> > + *
> > + * Linux EFI stub v1.1 unconditionally enabled initrd command line loader,
> > + * which was previously gated by CONFIG_EFI_GENERIC_STUB_INITRD_CMDLINE_LOADER.
> > + *
> > + * Linux EFI stub v3.0 changed the major version to be a bitfield (0b11).
> > + * The rightmost bit means that it is compatible with v1.0 at least.
> > + * The second rightmost bit means that initrd command line loader is enabled.
> > + * So, there is no v2.0 (0b10), and the next version will be v7.0 (0b111).
> > + */
> > +#define LINUX_EFISTUB_MAJOR_VERSION            0x3
> > +
> > +/*
> > + * LINUX_EFISTUB_MINOR_VERSION is pinned to 0x0, because Apple's
> > + * VZLinuxBootLoader cannot boot a kernel with other minor version value, even
> > + * though it does not use UEFI. Tested with macOS 13.4 (x86_64).
> > + *
> > + * https://lore.kernel.org/linux-efi/CAG8fp8Teu4G9JuenQrqGndFt2Gy+V4YgJ=hN1xX7AD940YKf3A@mail.gmail.com/
> >   */
> > -#define LINUX_EFISTUB_MAJOR_VERSION            0x1
> > -#define LINUX_EFISTUB_MINOR_VERSION            0x1
> > +#define LINUX_EFISTUB_MINOR_VERSION            0x0
> >
> >  /*
> >   * LINUX_PE_MAGIC appears at offset 0x38 into the MS-DOS header of EFI bootable
> > --
> > 2.39.2