linux-kernel - Re: [PATCH v8 00/23] efi/x86: Avoid bare metal decompressor during EFI boot

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Message-ID: <CAMj1kXEFC6LwNiWrGGsXot4SO0wivqN_3Yi=T9OS0XJ4=MeNew@mail.gmail.com>
Date:   Sat, 5 Aug 2023 19:37:17 +0200
From:   Ard Biesheuvel <ardb@...nel.org>
To:     Borislav Petkov <bp@...en8.de>
Cc:     linux-efi@...r.kernel.org, linux-kernel@...r.kernel.org,
        Evgeniy Baskov <baskov@...ras.ru>,
        Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Alexey Khoroshilov <khoroshilov@...ras.ru>,
        Peter Jones <pjones@...hat.com>,
        Gerd Hoffmann <kraxel@...hat.com>,
        Dave Young <dyoung@...hat.com>,
        Mario Limonciello <mario.limonciello@....com>,
        Kees Cook <keescook@...omium.org>,
        Tom Lendacky <thomas.lendacky@....com>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Joerg Roedel <jroedel@...e.de>
Subject: Re: [PATCH v8 00/23] efi/x86: Avoid bare metal decompressor during
 EFI boot

On Sat, 5 Aug 2023 at 16:41, Borislav Petkov <bp@...en8.de> wrote:
>
> On Wed, Aug 02, 2023 at 05:48:08PM +0200, Ard Biesheuvel wrote:
> > Update the x86 boot path to avoid the bare metal decompressor when
> > booting via the EFI stub. The bare metal decompressor inherits the
> > loader's 1:1 mapping of DRAM when entering in 64-bit mode, and assumes
> > that all of it is mapped read/write/execute, which will no longer be the
> > case on systems built to comply with recently tightened logo
> > requirements (*).
> >
> > Changes since v7 [10]:
>
> My Zen1 box fails booting with those. It is related to memory encryption
> because if I supply "mem_encrypt=off", it boots.
>
> The failure is (typing it off from the video from the BMC):
>
> /dev/root: Can't open blockdev
> VFS: Cannot open root device "UUID=..."
> Please append a correct "root=" boot option;
> ...
>
> I'll bisect now but it is pretty clear which one is the culprit.
>

So this is the host booting, right? So is the position of the C bit
perhaps getting detect incorrectly?