From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from desiato.infradead.org (desiato.infradead.org [90.155.92.199]) (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 4323620F07D for ; Tue, 6 May 2025 07:45:05 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=90.155.92.199 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1746517507; cv=none; b=cSiVBHZKynZDuYXNArIDZL9molxpjB7TMcU1M965tudUZ6/mOIAzo0I0xzRIiUAUB40qep5jdksLUdGZz6IypJWVS32pRkbAtWDS+cY1pC3VeCunoTobjX268ZkCyo6c4F/C8t///XmzmwkrpjX3qbb/lzhE/Tyybw8eRf5HQw0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1746517507; c=relaxed/simple; bh=dWeIEVlsTt6LZ7zYC8dLBPwWzYFzHO3Zjs5e8jZVlL4=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=pn1FBS2YFZp5oBEzZo1PN3OvZP8W2ZqKnacW5fKEk5ybwAmjnKmzMLEJMQPk658X+ZkfwEga6oAsU6gnLv26uqLbxmlxRwcuwfQX3YtGOj9Dmd311oiWJIwbLGiRwvD4/62BEXkUv0oUh04lKZVE0sGq1Qi6SsUcpRB2qas2l4E= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org; spf=none smtp.mailfrom=infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=WJPFbKvT; arc=none smtp.client-ip=90.155.92.199 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="WJPFbKvT" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=17qveg2sFxnYGJmZxV7vmqyNaQiuU15VOdXUcfpSCtM=; b=WJPFbKvTMZPkHD3L1BKzN5a/3E cJClJY9ZaJr7DB0omR9kpIJ8y1EQeAr4UuY2VVLtD45fGBBxIcbw+xrbXMCkqckwxcXgJv7jY1P63 TNjpSr+fx7rd/tEs8M5qea053wCRjpkn3AJyRuVP3i5OiV6kR33fTDFF1crCubHKj/jRT/KMuTmh3 hWHeTBmJl3Dh5Ra4Q8S3KInyjz3NVYg8bIHZ9y9FjYiGC5NS+cAE933/IX6tCvwybe7gXhLEjHEVl 8T83EuBGkuIa4fp+KFtYnwP91HF16/MXkK0YhN68u45xKrhzQLyOZPcekXUo402H18WHUPZZQg3Mt b6gJu3Hg==; Received: from 77-249-17-252.cable.dynamic.v4.ziggo.nl ([77.249.17.252] helo=noisy.programming.kicks-ass.net) by desiato.infradead.org with esmtpsa (Exim 4.98.1 #2 (Red Hat Linux)) id 1uCCz7-0000000Fc0t-0QDd; Tue, 06 May 2025 07:45:02 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id AB8BB30050D; Tue, 6 May 2025 09:45:00 +0200 (CEST) Date: Tue, 6 May 2025 09:45:00 +0200 From: Peter Zijlstra To: Ingo Molnar Cc: linux-kernel@vger.kernel.org, "H . Peter Anvin" , Linus Torvalds , Borislav Petkov , Thomas Gleixner Subject: Re: [PATCH 00/15] x86/kconfig: Enable various kernel features in the defconfig, add the 'x86_32' subarchitecture build target and misc cleanups Message-ID: <20250506074500.GI4198@noisy.programming.kicks-ass.net> References: <20250505110946.1095363-1-mingo@kernel.org> 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: <20250505110946.1095363-1-mingo@kernel.org> On Mon, May 05, 2025 at 01:09:31PM +0200, Ingo Molnar wrote: > Historically the x86 defconfigs aimed to be distro kernel > work-alikes with fewer drivers and a substantially shorter > build time. We regularly ask our contributors to test their > changes on x86 defconfigs, and we frequently analyze code > generation on such kernels as well. > > In practice, over the past couple of years this goal has > diverged from what actual modern Linux distributions do > these days, and this series aims to correct that divergence. > > Perform a thorough modernization of the x86 defconfigs, and > apply some cleanups to the x86 build system as well: > > - Enable various kernel features that the most popular > Linux distributions have enabled in their generic > kernels these days: KVM host, BPF support, UBSAN, various MM > options, debugging options, various scheduler and cgroups > options, support for a number of guest OS platforms, > and other options. > > - More specifically, these changes enable a rough superset > of the kernel features enabled by Ubuntu, Fedora/RHEL > kernels. > > - Clean up the organization of the defconfig files as well. > > - Add the ARCH=x86_32 build target > > - Synchronize the x86_32 defconfig to the x86_64 defconfig: > this file is really just a random set of options configured > many years ago with no relevance to anything people are > using today anymore. Just follow the 64-bit options to the > extent possible, to have at least one modern frame of > reference. > > - Clean up a number of kbuild details One thing I'd been pondering for a while, but have absolutely no bandwidth for what so ever, is a more fragment based config setup. Much like we now have defconfig, kvm_guest.config, debug.config and xen.config etc.. My main 'complain' is more that defconfig is too fat already, and here you are making it fatter still -- notably, I don't need i915 in most of the kernels I build (my test machines are all headless). Could we not instead move things out into fragments, so that people can compose the bits they need? The other day, I was looking for a kvm_host.config fragment, to pair with the kvm_guest.config we do have. Similarly, all that UBSAN, MM and assorted debug cruft is already in debug.config (although I do think debug.config is *too* heavy).