From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 52E17C83F17 for ; Wed, 30 Aug 2023 18:29:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238787AbjH3GeN (ORCPT ); Wed, 30 Aug 2023 02:34:13 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56992 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233464AbjH3Gdx (ORCPT ); Wed, 30 Aug 2023 02:33:53 -0400 Received: from bombadil.infradead.org (bombadil.infradead.org [IPv6:2607:7c80:54:3::133]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B3F84107 for ; Tue, 29 Aug 2023 23:33:50 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20210309; 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=wRGzirD/pbNMKYQh03dIBe/iW+yiXPUE4OYe0WqF7kY=; b=Ma80+8tmmfbpvy3TEkousI5DG0 D/H2I8FgPjh9xuV1miXyzjgcAiRPSYWR0UlwfOdRwO0TyYWKvZOXMMC5ZJNVkij6pwC+uiqqmmdJg L56vxc0hwG4Z634E0fofjnj8LjAd/2vZaikFqLwzvEDqUTIktw2ZcJzLY8Lh/XXEDgK6HVXFkzGZu z4cnOlOq/zMzT6MgfENpkU3946OYjVKVgOWbt3A6SzMS2O3iwWKvxkji2R1ADNMfl7je4HEW75OeS niMixJbimYHKA25Z0aWd5TjZv9k0nO61iNKThSix0URg0vIP4D3GpthgCTtAUEPuV3h7/u/cd+zen G/JCZnOw==; Received: from hch by bombadil.infradead.org with local (Exim 4.96 #2 (Red Hat Linux)) id 1qbElv-00CvOx-2Q; Wed, 30 Aug 2023 06:33:47 +0000 Date: Tue, 29 Aug 2023 23:33:47 -0700 From: Christoph Hellwig To: Linus Torvalds Cc: Christoph Hellwig , linux-kernel@vger.kernel.org, iommu@lists.linux.dev, Petr Tesarik , Yajun Deng Subject: Re: [GIT PULL] dma-mapping updates for Linux 6.6 Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Aug 29, 2023 at 08:54:43PM -0700, Linus Torvalds wrote: > > Yajun Deng (2): > > dma-contiguous: support per-numa CMA for all architectures > > What? > > This commit seems entirely bogus and is actively misleading. > > It claims to enable support for per-numa CMA for all architectures. > > It does no such thing. It actually does.. > All it does is to change the default value for a config option. It was > perfectly available before, now it is - incorrectly - made 'default y' > in case the config supports NUME at all. It also changes the default, and maybe that shouldn't have been, but that's not the meat of the change. The big part of the change is that the logic to actually reserve the per-node CMA area is now called from common code instead of arm64 code. Before you could have enable the option, but it wouldn't have worked at all. > > There seems to be no real reason to change the default value of this > config option. The commit message most definitely doesn't argue for > it, since it talks about something entirely different than what the > code changes does. > > I have taken this, but I protest these kinds of nonsensical changes. > That commit is actively misleading and confused, and I think the > default value for that config option should just be 'n' on all > architectures. > > Why is this option so important that it should be enabled just because > some minimal NUMA support might be enabled? > > Please don't add these kinds of hidden "default y" by making them > default on some much more common option instead. I think everyone including the maintainer was confused when the initial arm64 only version was merged by adding the default, it should have been a depends to start with. So we'll change this to a depends in a follow up.