From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail.avm.de (mail.avm.de [212.42.244.119]) (using TLSv1.2 with cipher DHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 6725353D0CB for ; Fri, 11 Sep 2026 19:34:26 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=212.42.244.119 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789155279; cv=none; b=NOETG7aoN+ycFeAySpx6mdFdN/8uCm5qfDeXY5ZnhNL36aZikoGXsew4g/W7NkXE0fY5H7Kpu0Sfmtb709k/PIQQlJXGYDy0dFmS5FBsQXBC7SeVhvllMv/3ZWVkKCYmtzGy9sUCAI3XsWGDWtnJWsS4VLKn/W6kac/Wb9bO3rY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789155279; c=relaxed/simple; bh=1JfbmLy+b2xGLH17ANL6tQt8xAUXkYVFyRMRSFYKTI8=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=gei0FNo0p3KwY/g9M48qSUYy3ww46gQGGrG02cshHJpc/oNDdDuoXBZHLm7Vg9xRqk6XgPULMhOcABj1Wvsg2FMasmSg06BCGCanewIWgPgm38truMymycuXwlcfpsAOFdnu2QPSUsLElJ9D95pkPYJoMj89+n0ge7PpjSbJzhA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=fritz.com; spf=pass smtp.mailfrom=fritz.com; dkim=pass (2048-bit key) header.d=fritz.com header.i=@fritz.com header.b=FhnZcspB; arc=none smtp.client-ip=212.42.244.119 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=fritz.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=fritz.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=fritz.com header.i=@fritz.com header.b="FhnZcspB" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=fritz.com; s=mail; t=1789155262; bh=1JfbmLy+b2xGLH17ANL6tQt8xAUXkYVFyRMRSFYKTI8=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=FhnZcspBrpigELbZTgL3IYBI0b+pFDqdiLuNUuMEvP1XCe3lb8wJ35046eFcsSlJv 6ly2ytvvQtvbyiWv6X2+0OM74cilE326ACJHMCheipzLn0tIWeTUo+b5OBdSyh2bH0 WyxyJXMmzBTzMLPFtiK+a5hx1kJyf6Uluud9RT3qAQe/f7lnqJI6E8x749lE+1GJKx yCJcYDWKy/eRMhv63UeDEuL7M2u3eTE2ik8Kak8gec8vyjYrVhK/hjjE7re9rqOOQ3 Yt6uFUsJKm+lGKHzCkP/TOzn5zSViKBtjcAMf7qaK7wthDOMSth5CVx+0gr36hV3i3 iC02B5tSCJjqg== Received: from [212.42.244.78] (helo=mail.avm.de) by mail.avm.de with ESMTP (eXpurgate 4.57.1) (envelope-from ) id 6aa457be-ea3f-7f0000032729-7f000001ab2c-1 for ; Fri, 11 Sep 2026 21:34:22 +0200 Received: from mail-auth.fritz.com (unknown [212.42.244.78]) by mail.avm.de (Postfix) with ESMTPS; Fri, 11 Sep 2026 21:34:22 +0200 (CEST) Date: Fri, 11 Sep 2026 21:34:21 +0200 From: Nicolas Schier To: "Lorenzo Stoakes (ARM)" Cc: David Laight , 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: <20260911-just-vanilla-seal-ea4f6a@l-nschier-aarch64> 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> <20260911183333.1df0f2e2@pumpkin> <20260911-invaluable-indigo-seal-e31aec@l-nschier-aarch64> Precedence: bulk X-Mailing-List: rust-for-linux@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: Organization: FRITZ! Technology GmbH x-ms-reactions: disallow X-purgate-ID: 149429::1789155262-66CC5720-882399CB/0/0 X-purgate-type: clean X-purgate-size: 1635 X-Notice: Whitelisted X-purgate: This mail is considered clean (visit https://www.eleven.de for further information) X-purgate: clean X-pfmilter: host: postfix-mx-02 mail-id: 8C75BA0467 external: no On Fri, Sep 11, 2026 at 07:24:50PM +0100, Lorenzo Stoakes (ARM) wrote: > On Fri, Sep 11, 2026 at 08:17:57PM +0200, Nicolas Schier wrote: > > On Fri, Sep 11, 2026 at 06:33:33PM +0100, David Laight wrote: > > > On Thu, 10 Sep 2026 17:42:35 +0200 > > > Nicolas Schier wrote: > > > > > > ... > > > > 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. > > > > > > One problem is that distributions have a nasty habit of shipping kernels > > > that are compiled with a different compiler version to they actually > > > ship as a compiler. > > > In some cases the versions are clearly the same - but the version > > > strings differ. > > > > yeah, I guess you hit the mark. > > I mean this is a problem that already exists for any flags already specified in > Kconfig. > > Out-of-tree modules are historically something that we don't go to great lengths > to support and haven't historically worried about breaking, either. > > I'm sure distros can find ways around this if a problem were to arise. But I > don't think it's something to worry about all that much. > > I expect a _lot_ of these, in any case, would only require the compilers to be > within a fair few major versions of one another anyway. yes, I have similar thoughts about that. But I think it's good that it has been mentioned here in public. -- Nicolas