linux-kernel - Re: [PATCHv13 4/9] x86/boot/compressed: Handle unaccepted memory

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Message-ID: <20230602164533.GHZHocre9bsQsU5L4+@fat_crate.local>
Date:   Fri, 2 Jun 2023 18:45:33 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Ard Biesheuvel <ardb@...nel.org>
Cc:     "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...el.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Joerg Roedel <jroedel@...e.de>,
        Andi Kleen <ak@...ux.intel.com>,
        Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        David Rientjes <rientjes@...gle.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Tom Lendacky <thomas.lendacky@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Ingo Molnar <mingo@...hat.com>,
        Dario Faggioli <dfaggioli@...e.com>,
        Mike Rapoport <rppt@...nel.org>,
        David Hildenbrand <david@...hat.com>,
        Mel Gorman <mgorman@...hsingularity.net>,
        marcelo.cerri@...onical.com, tim.gardner@...onical.com,
        khalid.elmously@...onical.com, philip.cox@...onical.com,
        aarcange@...hat.com, peterx@...hat.com, x86@...nel.org,
        linux-mm@...ck.org, linux-coco@...ts.linux.dev,
        linux-efi@...r.kernel.org, linux-kernel@...r.kernel.org,
        Liam Merwick <liam.merwick@...cle.com>
Subject: Re: [PATCHv13 4/9] x86/boot/compressed: Handle unaccepted memory

On Fri, Jun 02, 2023 at 06:17:13PM +0200, Ard Biesheuvel wrote:
> 'EFI code' is ambiguous here.
> 
> Most of the decompressor code is constructed in a way that permits
> - booting 'native EFI' via the EFI stub
> - booting 'pseudo-EFI' where GRUB or another Linux/x86 specific
> bootloader populates boot_params with all the EFI specific information
> (system table, memory map, etc)
> 
> This distinction has been abstracted away here, and so we might be
> dealing with the second case, and booting from a GRUB that does not
> understand accepted memory, but simply copied the EFI memory map
> (including unaccepted regions) as it normally does. (Note that the
> second case also covers kexec boot, so we do need to support it)

Right, I was hoping there to be some glue which sanity-checks
boot_params.efi_info instead relying on users to do so and thus have
a bunch of duplicated code.

So, yes, right after populating the boot_params pointer...

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette