linux-kernel - Re: [PATCH v2] x86/kexec: Add EFI config table identity mapping for kexec kernel

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Message-ID: <CAMj1kXEM5hGknVGwHh_w99D4L8yrYrTFycwGHZ0CQun70CLipw@mail.gmail.com>
Date:   Wed, 2 Aug 2023 16:55:27 +0200
From:   Ard Biesheuvel <ardb@...nel.org>
To:     Borislav Petkov <bp@...en8.de>
Cc:     Tom Lendacky <thomas.lendacky@....com>, Tao Liu <ltao@...hat.com>,
        Michael Roth <michael.roth@....com>, tglx@...utronix.de,
        mingo@...hat.com, dave.hansen@...ux.intel.com, x86@...nel.org,
        hpa@...or.com, linux-kernel@...r.kernel.org, bhe@...hat.com,
        dyoung@...hat.com, kexec@...ts.infradead.org,
        linux-efi@...r.kernel.org
Subject: Re: [PATCH v2] x86/kexec: Add EFI config table identity mapping for
 kexec kernel

On Wed, 2 Aug 2023 at 15:59, Borislav Petkov <bp@...en8.de> wrote:
>
> On Wed, Aug 02, 2023 at 08:40:36AM -0500, Tom Lendacky wrote:
> > Short of figuring out how to map page accesses earlier through the
> > boot_page_fault IDT routine
>
> And you want to do that because?
>

... because now, entering via startup_32 is broken, given that it only
maps the kernel image itself and relies on the #PF handling for
everything else it accesses, including firmware tables.

AFAICT this also means that entering via startup_32 is broken entirely
for any configuration that enables the cc blob config table check,
regardless of the platform.