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 X-Spam-Level: X-Spam-Status: No, score=-5.5 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B5E66C433E0 for ; Tue, 28 Jul 2020 12:22:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9B771206D4 for ; Tue, 28 Jul 2020 12:22:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729390AbgG1MWs (ORCPT ); Tue, 28 Jul 2020 08:22:48 -0400 Received: from verein.lst.de ([213.95.11.211]:48098 "EHLO verein.lst.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728300AbgG1MWr (ORCPT ); Tue, 28 Jul 2020 08:22:47 -0400 Received: by verein.lst.de (Postfix, from userid 2407) id E2E8B68B05; Tue, 28 Jul 2020 14:22:44 +0200 (CEST) Date: Tue, 28 Jul 2020 14:22:44 +0200 From: Christoph Hellwig To: "Song Bao Hua (Barry Song)" Cc: Christoph Hellwig , "m.szyprowski@samsung.com" , "robin.murphy@arm.com" , "will@kernel.org" , "ganapatrao.kulkarni@cavium.com" , "catalin.marinas@arm.com" , "iommu@lists.linux-foundation.org" , Linuxarm , "linux-arm-kernel@lists.infradead.org" , "linux-kernel@vger.kernel.org" , "Zengtao (B)" , huangdaode , Jonathan Cameron , Nicolas Saenz Julienne , Steve Capper , Andrew Morton , Mike Rapoport Subject: Re: [PATCH v4 1/2] dma-direct: provide the ability to reserve per-numa CMA Message-ID: <20200728122244.GA3639@lst.de> References: <20200723131344.41472-1-song.bao.hua@hisilicon.com> <20200723131344.41472-2-song.bao.hua@hisilicon.com> <20200728115231.GA793@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.17 (2007-11-01) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jul 28, 2020 at 12:19:03PM +0000, Song Bao Hua (Barry Song) wrote: > I am sorry I haven't got your point yet. Do you mean something like the below? > > arch/arm64/Kconfig: > config CMDLINE > string "Default kernel command string" > - default "" > + default "pernuma_cma=16M" > help > Provide a set of default command-line options at build time by > entering them here. As a minimum, you should specify the the > root device (e.g. root=/dev/nfs). Yes. > A background of the current code is that Linux distributions can usually use arch/arm64/configs/defconfig > directly to build kernel. cmdline can be easily ignored during the generation of Linux distributions. I've not actually heard of a distro shipping defconfig yet.. > > > if a way to expose this in the device tree might be useful, but people > > more familiar with the device tree and the arm code will have to chime > > in on that. > > Not sure if it is an useful user case as we are using ACPI but not device tree since it is an ARM64 > server with NUMA. Well, than maybe ACPI experts need to chime in on this. > > This seems to have lost the dma_contiguous_default_area NULL check. > > cma_alloc() is doing the check by returning NULL if cma is NULL. > > struct page *cma_alloc(struct cma *cma, size_t count, unsigned int align, > bool no_warn) > { > ... > if (!cma || !cma->count) > return NULL; > } > > But I agree here the code can check before calling cma_alloc_aligned. Oh, indeed. Please split the removal of the NULL check in to a prep patch then.