linux-kernel - Re: [PATCHv2 3/3] x86/64/mm: Make 5-level paging support unconditional

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Message-ID: <e5c5037f-6429-41bd-8166-de3aa1de01bd@suse.com>
Date: Fri, 16 May 2025 12:42:21 +0200
From: Jürgen Groß <jgross@...e.com>
To: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
 Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>,
 Borislav Petkov <bp@...en8.de>, Dave Hansen <dave.hansen@...ux.intel.com>,
 x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>
Cc: Jonathan Corbet <corbet@....net>, Andy Lutomirski <luto@...nel.org>,
 Peter Zijlstra <peterz@...radead.org>, Ard Biesheuvel <ardb@...nel.org>,
 Jan Kiszka <jan.kiszka@...mens.com>, Kieran Bingham <kbingham@...nel.org>,
 Michael Roth <michael.roth@....com>,
 Rick Edgecombe <rick.p.edgecombe@...el.com>,
 Brijesh Singh <brijesh.singh@....com>, Sandipan Das <sandipan.das@....com>,
 Tom Lendacky <thomas.lendacky@....com>, linux-kernel@...r.kernel.org,
 linux-doc@...r.kernel.org, linux-efi@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCHv2 3/3] x86/64/mm: Make 5-level paging support
 unconditional

On 16.05.25 11:15, Kirill A. Shutemov wrote:
> Both Intel and AMD CPUs support 5-level paging, which is expected to
> become more widely adopted in the future.
> 
> Remove CONFIG_X86_5LEVEL and ifdeffery for it to make it more readable.
> 
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
> Suggested-by: Borislav Petkov <bp@...en8.de>
> ---
>   Documentation/arch/x86/cpuinfo.rst            |  8 +++----
>   .../arch/x86/x86_64/5level-paging.rst         |  9 --------
>   arch/x86/Kconfig                              | 22 +------------------
>   arch/x86/Kconfig.cpufeatures                  |  4 ----
>   arch/x86/boot/compressed/pgtable_64.c         | 11 ++--------
>   arch/x86/boot/header.S                        |  4 ----
>   arch/x86/boot/startup/map_kernel.c            |  5 +----
>   arch/x86/include/asm/page_64.h                |  2 --
>   arch/x86/include/asm/page_64_types.h          |  7 ------
>   arch/x86/include/asm/pgtable_64_types.h       | 18 ---------------
>   arch/x86/kernel/alternative.c                 |  2 +-
>   arch/x86/kernel/head64.c                      |  2 --
>   arch/x86/kernel/head_64.S                     |  2 --
>   arch/x86/mm/init.c                            |  4 ----
>   arch/x86/mm/pgtable.c                         |  2 +-
>   drivers/firmware/efi/libstub/x86-5lvl.c       |  2 +-
>   16 files changed, 10 insertions(+), 94 deletions(-)

There are some instances of:

#if CONFIG_PGTABLE_LEVELS >= 5

in 64-bit-only code under arch/x86, which could be simplified, too.

They are still correct, but I wanted to hint at further code removals
being possible.

Juergen

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