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

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Date:   Sat, 3 Jun 2023 00:52:33 +0200
From:   Ard Biesheuvel <ardb@...nel.org>
To:     Akihiro Suda <suda.kyoto@...il.com>
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

On Fri, 2 Jun 2023 at 22:30, Akihiro Suda <suda.kyoto@...il.com> wrote:
>
> > > 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
>
> Thank you for rewriting my comments, but the new comments seem
> slightly incorrect:
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=36e4fc57fc1619f462e669e939209c45763bc8f5
>
> > efi: Bump stub image version for macOS HVF compatibility
>
> The commit is about Virtualization.framework, not about
> Hypervisor.framework (HVF).
>
> Virtualization.framework = high-level VMM, similar to QEMU
> (/usr/bin/qemu-system-*)
> Hypervisor.framework     = low-level  VMM, similar to kvm.ko
>
> > The macOS hypervisor framework includes a host-side VMM called VZLinuxBootLoader
>
> VZLinuxBootLoader is a part of Virtualization.framework, not
> Hypervisor.framework.
> Also, VZLinuxBootLoader is not a VMM; it is just an API for loading
> vmlinuz into Virtualization.framework.
> (similar to the `-kernel` and the `-initrd` flags of QEMU)
>

Apologies for these mistakes. Unfortunately, this patch has been
merged now so there is nothing we can do about it.

> > On x86, it incorporates a BIOS style loader that does not implement or expose EFI to the loaded kernel.
>
> AFAICS, it does not seem to use real mode BIOS.
>

I never mentioned real mode, did I?