linux-kernel - Re: [PATCH v5 0/2] kbuild: distributed build support for Clang ThinLTO

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Message-ID: <20251204174954.GA1177092@ax162>
Date: Thu, 4 Dec 2025 10:49:54 -0700
From: Nathan Chancellor <nathan@...nel.org>
To: xur@...gle.com
Cc: Masahiro Yamada <masahiroy@...nel.org>,
	Nicolas Schier <nicolas.schier@...ux.dev>,
	Nick Desaulniers <nick.desaulniers+lkml@...il.com>,
	Bill Wendling <morbo@...gle.com>,
	Justin Stitt <justinstitt@...gle.com>,
	Miguel Ojeda <ojeda@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Alice Ryhl <aliceryhl@...gle.com>,
	Sami Tolvanen <samitolvanen@...gle.com>,
	"Mike Rapoport (Microsoft)" <rppt@...nel.org>,
	Rafael Aquini <aquini@...hat.com>,
	Michael Ellerman <mpe@...erman.id.au>,
	Stafford Horne <shorne@...il.com>,
	Christophe Leroy <christophe.leroy@...roup.eu>,
	Piotr Gorski <piotrgorski@...hyos.org>,
	Teresa Johnson <tejohnson@...gle.com>, linux-kernel@...r.kernel.org,
	linux-kbuild@...r.kernel.org, llvm@...ts.linux.dev
Subject: Re: [PATCH v5 0/2] kbuild: distributed build support for Clang
 ThinLTO

Hi Rong,

On Tue, Oct 28, 2025 at 06:28:20PM +0000, xur@...gle.com wrote:

First of all, my apologies for taking so long to get to testing and
reviewing this patchset.

> Rong Xu (2):
>   kbuild: move vmlinux.a build rule to scripts/Makefile.vmlinux_a
>   kbuild: distributed build support for Clang ThinLTO
> 
>  .gitignore                 |  2 +
>  Makefile                   | 25 +++++-------
>  arch/Kconfig               | 19 +++++++++
>  scripts/Makefile.lib       |  7 ++++
>  scripts/Makefile.thinlto   | 40 ++++++++++++++++++
>  scripts/Makefile.vmlinux_a | 83 ++++++++++++++++++++++++++++++++++++++
>  scripts/mod/modpost.c      | 15 +++++--
>  7 files changed, 174 insertions(+), 17 deletions(-)
>  create mode 100644 scripts/Makefile.thinlto
>  create mode 100644 scripts/Makefile.vmlinux_a

Overall, this seems reasonable from a high level perspective. I have
been testing it with my arm64 and x86_64 distribution configurations for
the past couple of days and I have not noticed any issues.

Did you take a look at the robot report from patch 2?

  https://lore.kernel.org/202511052257.Bb85ptQG-lkp@intel.com/

It seems like it could be caused by different optimizations?

I plan to take a more in-depth look at the implementation after I am
back home from Plumbers in a couple of weeks (just to make sure I
understand it from a maintainer's perspective). Based on that, I will
either apply it to kbuild-next for 6.20/7.0 or ask for further
interations, while still aiming to get it into that release.

Cheers,
Natha