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 609A535C6B2; Fri, 11 Sep 2026 18:25:45 +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=1789151146; cv=none; b=hTR3n1TJ8FfMDKFfzwQjvt/hDDCzKPQlNrZ20Ogw87FoCpy/60lc9+R/7odPCTBWNpvOR5TRuPuRY8Nedb9LMhM5WX3j5mUaA5EAphxE+4scI88NmCRomNRJ5Y4KvseBufWIWXjUkb0zIcKdhy4bBd7fKSAPDIfHhINgcm3OZ8o= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789151146; c=relaxed/simple; bh=GkMDfaiKqcg6wNo9HFZUrY6MjHcj3UzMmujQXp5hqko=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=SiUkCpdmak0tfokiKYwROW7ftkNbslPFxzNMcH/ihJrLKYbayWONul5P6IntXmsdottqROsbMFAoDauPFc38oz42UXA8/kLomXBsVqoQDRNHA1uQm+EZr2JDu9kbl6N5dKNBssu5p+/mNaIObaCGXa9kI1rAGO19T1HEinDa1RE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=V/QuD7RK; 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="V/QuD7RK" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8FF181F000FF; Fri, 11 Sep 2026 18:25:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1789151145; bh=McB2i4WG3qj3jgvtyEEzwZVFRWbrW+2vNGQO4jJcnEw=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=V/QuD7RKHTWhky3dgb6PVRJNvxWnkze0kt4kkrpUnCYoPR2W7r5F4K2sjrh7TCfss 3ahJS7dH3z937W49lrR506NxxwHhwI7zdRL6r32SGdlPGna39Rpd+/8rNoR29ffA/j UVSXzAGjyvuBP1ddhf9lUq9UVY9KejS9z7yop3ddDfhfsHmy2ebKxvWsoDTbtYtpPH 2EQmQxGv0R8uinJ5AuwYTYO0/VrdPdDWzjtZjDh4ANe9EnGlPpC3NQn91JHsCLyMS4 p/V7dx1LnhW4eNnz1YJP70OKAqj3ALNE8aIfNZa1yGBV5DzFRtttI6lrWcB+hRAAH0 T3mOd8cIXS22A== Date: Fri, 11 Sep 2026 19:25:32 +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> <20260911-mottled-gerbil-of-abracadabra-bacb17@l-nschier-aarch64> Precedence: bulk X-Mailing-List: linux-arch@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: <20260911-mottled-gerbil-of-abracadabra-bacb17@l-nschier-aarch64> On Fri, Sep 11, 2026 at 08:10:26PM +0200, Nicolas Schier wrote: > On Fri, Sep 11, 2026 at 11:30:12AM +0100, Lorenzo Stoakes (ARM) wrote: > > 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? > > yes, sure. > > > > > > > > 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? > > I don't think it has to be part of the series, it's long enough already. > But if you want to prepare some docmentation about the preference of > cc-option checks, feel free to go ahead or not. Ack, thanks! > > Kind regards > Nicolas -- Cheers, Lorenzo