From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 9631443CEF3; Fri, 11 Sep 2026 10:30:26 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789122628; cv=none; b=o7D6dh/L6yz7SYbgbvQnUcLsmt/FBE+h9Io+FAZPUXc7mOmIZcHET4WoLx8qdbBRfOwJxameO2VrudbtjzHLAbaHTDZNhaY5pY7BM+fqGgxt2l2Ao/ndTLcb0vEMFvj61475WFiAK/WaicCWWGQz6EI/ln3mRzhiqvSrBGrG0GE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789122628; c=relaxed/simple; bh=fJLjHJ4Zesn9ZGCkyFCEtE1u8yd+UsBqa01I0/KBdbc=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=PadOpuUSiNZVvQ4OF7IT1EKZ5hyLbInk0q++rKCEe8ZnqbB7x/KCoMsPcGUluwdwk9BtPAlv0l1XnpSczKa4GaQ8KpZMf9V+m2vvRj7uhJC/DzNsfcPEcPK+S4BfSYt6ACE1M0hJgPqKQW21Dg3gguG5YJw0nGl5a4xR7B84Koc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=JZS/pO7H; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="JZS/pO7H" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2D4EE1F00893; Fri, 11 Sep 2026 10:30:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1789122626; bh=HvFCGCANaLFVV/N2IK8KH4LaOjgAeqgCzbjmvYneKXY=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=JZS/pO7H1pqAZlMiQfD69ngRhDMlBggb2cf7WXqq35hVdt6EJaURUBtmC4djm7YlO xyjg+nnrOjmg2UqBoa2RhbyP0vDv4NP7gutpfcXXNf8+8Jb7DARVGX5NbEmBeqrkhL J6WFa/UqRcOepTtPh7h7pANQKHrW3T9qJbQmAr+uJbt8OZbzEiWD4+lu0YVWY2Y7Vc ybOd5FOj4FYTQ20nMKw8qnkWY/MsN/C3euDfdcLLm0itz4z6/liMd1loce9nvjp4nb on/xsdRR27N/vMX5OG+ddPelyz4EOT6o95KJVuDyPXA1MiXZ9sjuF6rqvoqse3QloP 7P4oppuiKyBBw== Date: Fri, 11 Sep 2026 11:30:12 +0100 From: "Lorenzo Stoakes (ARM)" To: Nicolas Schier Cc: Nathan Chancellor , Linus Torvalds , Nick Desaulniers , Bill Wendling , Justin Stitt , Masahiro Yamada , Alexey Gladkov , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Paul Walmsley , Palmer Dabbelt , Albert Ou , Alexandre Ghiti , Arnd Bergmann , Catalin Marinas , Will Deacon , Mark Rutland , Ard Biesheuvel , Ilias Apalodimas , Josh Poimboeuf , Peter Zijlstra , Miguel Ojeda , Boqun Feng , Gary Guo , =?utf-8?B?QmrDtnJu?= Roy Baron , Benno Lossin , Andreas Hindborg , Alice Ryhl , Trevor Gross , Danilo Krummrich , Daniel Almeida , Tamir Duberstein , Alexandre Courbot , Onur =?utf-8?B?w5Z6a2Fu?= , Jonathan Corbet , Randy Dunlap , linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org, llvm@lists.linux.dev, linux-riscv@lists.infradead.org, linux-arch@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-efi@vger.kernel.org, rust-for-linux@vger.kernel.org, linux-doc@vger.kernel.org, Jens Axboe Subject: Re: [PATCH 12/23] kbuild: avoid re-running compiler and linker probes Message-ID: References: <20260908-build-speedup-v1-0-5dc1ac01672d@kernel.org> <20260908-build-speedup-v1-12-5dc1ac01672d@kernel.org> <178901395292.3971858.13236774094648272066.b4-review@b4> <20260910-translucent-sweet-sidewinder-7acacb@l-nschier-aarch64> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260910-translucent-sweet-sidewinder-7acacb@l-nschier-aarch64> On Thu, Sep 10, 2026 at 05:42:35PM +0200, Nicolas Schier wrote: > On Wed, Sep 09, 2026 at 09:19:12PM -0700, Nathan Chancellor wrote: > > > diff --git a/init/Kconfig b/init/Kconfig > > > index 8583d9f06c52..3c92c87254a3 100644 > > > --- a/init/Kconfig > > > +++ b/init/Kconfig > > > @@ -144,6 +144,44 @@ config CC_HAS_ASSUME > > > config CC_HAS_NO_PROFILE_FN_ATTR > > > def_bool $(success,echo '__attribute__((no_profile_instrument_function)) int x();' | $(CC) -x c - -c -o /dev/null -Werror) > > > > > > +config CC_HAS_ZERO_INIT_PADDING_BITS > > > + def_bool $(cc-option,-fzero-init-padding-bits=all) > > > + > > > +config CC_HAS_NO_STACK_CLASH_PROTECTION > > > + def_bool $(cc-option,-fno-stack-clash-protection) > > > + > > > +config CC_HAS_NO_ADDRSIG > > > + def_bool $(cc-option,-fno-addrsig) > > > > I am generally in favor of this proposal since I think these checks > > should be cached by Kconfig where possible to clear up running them > > twice. That said, I wonder if we should pick a better dumping ground for > > these checks other than init/Kconfig. Maybe init/Kconfig.tools or > > scripts/Kconfig.tools or something? > (Sorry hadn't seen you'd replied also!) > Yes, skimming through the patch, I thought about that, too. Moving more > cc option checks to Kconfig will make building out-of-tree kmods with a > different compiler more dangerous. Maybe we will have to make the > warning in Makefile's prepare (external kmods) target a bit louder. I guess this bit can be a follow up potentially? > > > I also worry about backsliding and growing cc-option checks. Should we > > update the documentation to state that it is preferrable for these > > checks to live in Kconfig so that they can be properly cached? > > Sounds good, yes. I can add a doc update as part of this series, unless you guys want to handle separately? > > -- > Nicolas -- Cheers, Lorenzo