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=-2.5 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, T_DKIMWL_WL_HIGH,URIBL_BLOCKED,USER_AGENT_MUTT autolearn=ham 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 5DB6BC04AB5 for ; Mon, 3 Jun 2019 10:52:13 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (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 2E287280D2 for ; Mon, 3 Jun 2019 10:52:13 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="tprf/yU4" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 2E287280D2 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=8bytes.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-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=bombadil.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=N7+un45Z5aanltQUJFUtZCuPjAKMWYWlOFEjJUiRMNE=; b=tprf/yU4E6fQ0B oOn0CfvIxpgFo96qKwjaTPPIBgegNWYNMyb3cOSSBDsottVq60kNYDiRzoPMy+HSoNcsKcrAMy18n 5H7TnVOhheB4H7eZMqsMroVnDwo/uycZixPmEK/k2xZCN7rfjEHgIHzKb3X5Ej3/j+5rK2fCBlv7p ib2KA1GtTXrUQWECl5AgukP/zkaaB1bvSXLoL5818fWevwHqVs1kgYvPXYq219Pt2y43xq1UR+c9X A2gjoaxhg26bXYlU/N9Bmt6etKvHU+UAmF315+4TaGjAbyzg6eURRAXlsM/DYXIOim2Ja3JVbckOS wd2W6d6LXejf7be5wN3g==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.90_1 #2 (Red Hat Linux)) id 1hXkZW-0007vU-Ti; Mon, 03 Jun 2019 10:52:10 +0000 Received: from 8bytes.org ([81.169.241.247] helo=theia.8bytes.org) by bombadil.infradead.org with esmtps (Exim 4.90_1 #2 (Red Hat Linux)) id 1hXkZS-0007uV-Nf; Mon, 03 Jun 2019 10:52:08 +0000 Received: by theia.8bytes.org (Postfix, from userid 1000) id C6EF836B; Mon, 3 Jun 2019 12:51:59 +0200 (CEST) Date: Mon, 3 Jun 2019 12:51:58 +0200 From: Joerg Roedel To: Tom Murphy Subject: Re: [PATCH v3 0/4] iommu/amd: Convert the AMD iommu driver to the dma-iommu api Message-ID: <20190603105158.GL12745@8bytes.org> References: <20190506185207.31069-1-tmurphy@arista.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20190506185207.31069-1-tmurphy@arista.com> User-Agent: Mutt/1.10.1 (2018-07-13) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190603_035206_922800_E0E965BD X-CRM114-Status: GOOD ( 10.63 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Heiko Stuebner , Will Deacon , David Brown , Thierry Reding , Marek Szyprowski , linux-s390@vger.kernel.org, linux-samsung-soc@vger.kernel.org, iommu@lists.linux-foundation.org, Krzysztof Kozlowski , Jonathan Hunter , linux-rockchip@lists.infradead.org, Kukjin Kim , Gerald Schaefer , Andy Gross , linux-tegra@vger.kernel.org, linux-arm-msm@vger.kernel.org, linux-mediatek@lists.infradead.org, Matthias Brugger , linux-arm-kernel@lists.infradead.org, Robin Murphy , linux-kernel@vger.kernel.org, murphyt7@tcd.ie, Rob Clark , David Woodhouse Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi Tom, On Mon, May 06, 2019 at 07:52:02PM +0100, Tom Murphy wrote: > Convert the AMD iommu driver to the dma-iommu api. Remove the iova > handling and reserve region code from the AMD iommu driver. Thank you for your work on this! I appreciate that much, but I am not sure we are ready to make that move for the AMD and Intel IOMMU drivers yet. My main concern right now is that these changes will add a per-page table lock into the fast-path for dma-mapping operations. There has been much work in the past to remove all locking from these code-paths and make it scalable on x86. The dma-ops implementations in the x86 IOMMU drivers have the benefit that they can call their page-table manipulation functions directly and without locks, because they can make the necessary assumptions. The IOMMU-API mapping/unmapping path can't make these assumptions because it is also used for non-DMA-API use-cases. So before we can move the AMD and Intel drivers to the generic DMA-API implementation we need to solve this problem to not introduce new scalability regressions. Regards, Joerg _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel