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, 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 26F27C433E1 for ; Thu, 23 Jul 2020 11:55:46 +0000 (UTC) Received: from whitealder.osuosl.org (smtp1.osuosl.org [140.211.166.138]) (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 EA57020684 for ; Thu, 23 Jul 2020 11:55:44 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org EA57020684 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=lst.de Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=iommu-bounces@lists.linux-foundation.org Received: from localhost (localhost [127.0.0.1]) by whitealder.osuosl.org (Postfix) with ESMTP id D7645898B3; Thu, 23 Jul 2020 11:55:44 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from whitealder.osuosl.org ([127.0.0.1]) by localhost (.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id uRUaSFqa3b17; Thu, 23 Jul 2020 11:55:43 +0000 (UTC) Received: from lists.linuxfoundation.org (lf-lists.osuosl.org [140.211.9.56]) by whitealder.osuosl.org (Postfix) with ESMTP id 65350898B6; Thu, 23 Jul 2020 11:55:43 +0000 (UTC) Received: from lf-lists.osuosl.org (localhost [127.0.0.1]) by lists.linuxfoundation.org (Postfix) with ESMTP id 3163EC004E; Thu, 23 Jul 2020 11:55:43 +0000 (UTC) Received: from silver.osuosl.org (smtp3.osuosl.org [140.211.166.136]) by lists.linuxfoundation.org (Postfix) with ESMTP id 53165C004C for ; Thu, 23 Jul 2020 11:55:41 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by silver.osuosl.org (Postfix) with ESMTP id 33F292C342 for ; Thu, 23 Jul 2020 11:55:41 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from silver.osuosl.org ([127.0.0.1]) by localhost (.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id l-kJk4baW3nD for ; Thu, 23 Jul 2020 11:55:32 +0000 (UTC) X-Greylist: from auto-whitelisted by SQLgrey-1.7.6 Received: from verein.lst.de (verein.lst.de [213.95.11.211]) by silver.osuosl.org (Postfix) with ESMTPS id DC86A29DD7 for ; Thu, 23 Jul 2020 11:55:31 +0000 (UTC) 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) Cc: "catalin.marinas@arm.com" , Steve Capper , "robin.murphy@arm.com" , Linuxarm , "linux-kernel@vger.kernel.org" , "iommu@lists.linux-foundation.org" , "Zengtao \(B\)" , "ganapatrao.kulkarni@cavium.com" , huangdaode , Andrew Morton , Mike Rapoport , "will@kernel.org" , Christoph Hellwig , "linux-arm-kernel@lists.infradead.org" X-BeenThere: iommu@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Development issues for Linux IOMMU support List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: iommu-bounces@lists.linux-foundation.org Sender: "iommu" 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. _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu