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,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,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 2E48DC433E4 for ; Thu, 23 Jul 2020 11:56:53 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id EE999206E3 for ; Thu, 23 Jul 2020 11:56:52 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="dyeY2AXP" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org EE999206E3 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=lst.de Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=merlin.20170209; h=Sender:Content-Transfer-Encoding: Content-Type:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References:Message-ID: Subject:To:From:Date:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=J/DpfhWKkTNEV8PE28YeKmXUxn7hIRaIiSUniHP9A1U=; b=dyeY2AXP5bFWMUwhVIalcbgZD OnVzgJuiwyGY4TyFw3A4RPLRXOmBEWKAQjJ4g8oZfhTGcrhAYTYhheziYXsin8vdW06S/0bFkcSHb UnvMCXmkPKPY0rd65cxQWAi6SASC2ZPWsawicZJo9Gtn/wrCtnAC8+svO4WNAWZEGn6VUCsvLJzoD 187R8UwMVWbE7u2y/dxu6xzEstXbls2LScKW13RVK/c+UWF0Vhq4XxkJd6xm/xeIGldig48rq6UMf W4JisTAEzIikWMPKDc64XdGFRESfbKJtl/kd/NM/BxK1OwSxD3HBWzTZcSXaieE4PjS1x02UyI/hF KNwyO2O5w==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jyZoz-0006Pf-3w; Thu, 23 Jul 2020 11:55:33 +0000 Received: from verein.lst.de ([213.95.11.211]) by merlin.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1jyZox-0006P3-8n for linux-arm-kernel@lists.infradead.org; Thu, 23 Jul 2020 11:55:32 +0000 Received: by verein.lst.de (Postfix, from userid 2407) id 6004C68AFE; Thu, 23 Jul 2020 13:55:27 +0200 (CEST) Date: Thu, 23 Jul 2020 13:55:27 +0200 From: Christoph Hellwig To: "Song Bao Hua (Barry Song)" Subject: Re: [PATCH v3 1/2] dma-direct: provide the ability to reserve per-numa CMA Message-ID: <20200723115527.GA31598@lst.de> References: <20200628111251.19108-1-song.bao.hua@hisilicon.com> <20200628111251.19108-2-song.bao.hua@hisilicon.com> <20200722141658.GA17658@lst.de> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.17 (2007-11-01) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200723_075531_432114_37D8C13B X-CRM114-Status: GOOD ( 13.38 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: "catalin.marinas@arm.com" , Steve Capper , "robin.murphy@arm.com" , Jonathan Cameron , Linuxarm , "linux-kernel@vger.kernel.org" , "iommu@lists.linux-foundation.org" , Nicolas Saenz Julienne , "Zengtao \(B\)" , "ganapatrao.kulkarni@cavium.com" , huangdaode , Andrew Morton , Mike Rapoport , "will@kernel.org" , Christoph Hellwig , "linux-arm-kernel@lists.infradead.org" , "m.szyprowski@samsung.com" Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Wed, Jul 22, 2020 at 09:26:03PM +0000, Song Bao Hua (Barry Song) wrote: > I understand your concern. Anyway, The primary purpose of this patchset is providing > a general way for users like IOMMU to get local coherent dma buffers to put their > command queue and page tables in. The first user case is what really made me > begin to prepare this patchset. > > For the second case, it is probably a positive side effect of this patchset for those users > who have more concern on performance than dma security, then they maybe skip > IOMMU by > iommu.passthrough= > [ARM64, X86] Configure DMA to bypass the IOMMU by default. > Format: { "0" | "1" } > 0 - Use IOMMU translation for DMA. > 1 - Bypass the IOMMU for DMA. > unset - Use value of CONFIG_IOMMU_DEFAULT_PASSTHROUGH. > In this case, they can get local memory and get better performance. > However, it is not the primary purpose of this patchset. That's not what I mean. Hardcoding the CMA regions in the kernel config is just a bad idea, and we should not add more hard coded values. You can always use CONFIG_CMDLINE to force a specific kernel command line including your options. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel