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From:   Ard Biesheuvel <ardb@kernel.org>
Date:   Tue, 22 Nov 2022 22:51:42 +0100
Message-ID: <CAMj1kXF7xj4BsB4nvFYGQNxGzSb2v=KGqzbjMc5tzXWy9i1FAQ@mail.gmail.com>
Subject: Re: [PATCH v3 00/17] x86: head_64.S spring cleaning
To:     Tom Lendacky <thomas.lendacky@amd.com>
Cc:     linux-efi@vger.kernel.org, linux-kernel@vger.kernel.org,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Michael Roth <michael.roth@amd.com>
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On Tue, 22 Nov 2022 at 22:51, Tom Lendacky <thomas.lendacky@amd.com> wrote:
>
> On 11/22/22 15:42, Ard Biesheuvel wrote:
> > On Tue, 22 Nov 2022 at 22:37, Ard Biesheuvel <ardb@kernel.org> wrote:
> >>
> >> On Tue, 22 Nov 2022 at 21:48, Tom Lendacky <thomas.lendacky@amd.com> wrote:
> >>>
> >>> On 11/22/22 10:10, Ard Biesheuvel wrote:
> >>>> After doing some cleanup work on the EFI code in head_64.S, the mixed
> >>>> mode code in particular, I noticed that the memory encryption pieces
> >>>> could use some attention as well, so I cleaned that up too.
> >>>>
> >>>> Changes since v2:
> >>>> - add some clarifying comments to the EFI mixed mode changes
> >>>> - include patch to make the EFI handover protocol optional that was sent
> >>>>     out separately before
> >>>> - rebase onto tip/master
> >>>>
> >>>> Changes since v1:
> >>>> - at Boris's request, split the patches into smaller ones that are
> >>>>     easier to review
> >>>>
> >>>> Cc: Thomas Gleixner <tglx@linutronix.de>
> >>>> Cc: Ingo Molnar <mingo@redhat.com>
> >>>> Cc: Borislav Petkov <bp@alien8.de>
> >>>> Cc: Dave Hansen <dave.hansen@linux.intel.com>
> >>>> Cc: Michael Roth <michael.roth@amd.com>
> >>>
> >>> This causes an SEV guest to blow up on boot in the early boot code. It
> >>> looks like the stack pointer is not valid and it triple faults on a pushq
> >>> instruction (pushq $__KERNEL_CS in arch/x86/boot/compressed/head_64.S of
> >>> startup_64).
> >>>
> >>
> >> Thanks for the report.
> >>
> >> So the mystery here (at least to me) is that all the changes are to
> >> the 32-bit code, and startup_64 reloads the stack pointer from the
> >> symbol
> >>
> >> Does your config have CONFIG_EFI_MIXED enabled?
> >>
> >> Can I reproduce this fully emulated with QEMU? Or do I need a SEV host?
> >>
> >
> > Also, mind giving this a quick spin?
>
> Just saw this after I sent out my email. Yes, this fixes it.
>

Excellent, thanks for testing.