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 smtp1.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 smtp.lore.kernel.org (Postfix) with ESMTPS id 4A304C433F5 for ; Wed, 6 Apr 2022 14:24:43 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by smtp1.osuosl.org (Postfix) with ESMTP id E755B813C5; Wed, 6 Apr 2022 14:24:42 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from smtp1.osuosl.org ([127.0.0.1]) by localhost (smtp1.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 4hW4mokkiZGG; Wed, 6 Apr 2022 14:24:42 +0000 (UTC) Received: from lists.linuxfoundation.org (lf-lists.osuosl.org [140.211.9.56]) by smtp1.osuosl.org (Postfix) with ESMTPS id C0C0B813D6; Wed, 6 Apr 2022 14:24:41 +0000 (UTC) Received: from lf-lists.osuosl.org (localhost [127.0.0.1]) by lists.linuxfoundation.org (Postfix) with ESMTP id 8D7A7C002C; Wed, 6 Apr 2022 14:24:41 +0000 (UTC) Received: from smtp3.osuosl.org (smtp3.osuosl.org [140.211.166.136]) by lists.linuxfoundation.org (Postfix) with ESMTP id 4D55AC0012; Wed, 6 Apr 2022 14:24:39 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by smtp3.osuosl.org (Postfix) with ESMTP id 2BA7F60BD8; Wed, 6 Apr 2022 14:24:39 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Authentication-Results: smtp3.osuosl.org (amavisd-new); dkim=pass (2048-bit key) header.d=nvidia.com Received: from smtp3.osuosl.org ([127.0.0.1]) by localhost (smtp3.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id PpppgM8h127j; Wed, 6 Apr 2022 14:24:38 +0000 (UTC) X-Greylist: whitelisted by SQLgrey-1.8.0 X-Greylist: whitelisted by SQLgrey-1.8.0 Received: from NAM11-DM6-obe.outbound.protection.outlook.com (mail-dm6nam11on20608.outbound.protection.outlook.com [IPv6:2a01:111:f400:7eaa::608]) by smtp3.osuosl.org (Postfix) with ESMTPS id 5CF4160784; Wed, 6 Apr 2022 14:24:38 +0000 (UTC) ARC-Seal: i=1; a=rsa-sha256; s=arcselector9901; d=microsoft.com; cv=none; b=FPR1uDKmgNXOHJiYi/X0WY+KGSpItskwKY+x+iJfqw/4eNrUCAjgjrQIgdKZc7HKcYrRIqfWHFngZruQst4FKWuKTmsIJJZ9JTEmmM45LL02Ko6h6XCpSfOzcQxZFjF8LOp3jV4VFIHn+qh6SkM01p5HfMrU7Mz9XN+dKqGo53PiZEyUBeGP0i7P9VJ69UfZouW3qFxxtKoTsWRNLfd2l0Rv/XSnV9i3P3ykh4dVxQObQHWSUPLlu9YLCpyFtXFqL5rlAG3axksNE2BqQRIoOo8GgPraKafVXwazeh7H86GvR5omtf+HLgM3/FCT4CSSxCo4b/t94xCdk7Vv+agYWQ== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com; s=arcselector9901; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-AntiSpam-MessageData-ChunkCount:X-MS-Exchange-AntiSpam-MessageData-0:X-MS-Exchange-AntiSpam-MessageData-1; bh=1uYgX1e2UDd/ai7mblSLjuOtLmcj0q3PDcURNfc0AR8=; b=abgZWDRNWEvadotFNh2t6vzrArNqc4bV/lTwWRR5GilcLjTnr+1EG5orGPWPIdv7i1Qod2kvbfq4fUmFmn4m0kCpKp4Ik8VCIlYkjlvHwQj1CQy1aGe5n6EcTPU1mduwUZwJvtXqRYUq1fvqLPt7aoJcsgZOiZ6f8u5UD4Pk3IPBmguKP/bm3bWVzn4qoR5dB1VIMc84lOuiTjE8wEFxN4ugvF7WVzR/G5eLMdIZb6ZVW455nQ1LbTZ+waDA368mO+0PwSkHMjx0DQnb0TKr6bsID+qFjr0M3M64DiTX9G9fSmkRkbZhyROuKNIuO9jsA3vuO4JK0YysewPRW49PNQ== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass smtp.mailfrom=nvidia.com; dmarc=pass action=none header.from=nvidia.com; dkim=pass header.d=nvidia.com; arc=none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=Nvidia.com; s=selector2; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=1uYgX1e2UDd/ai7mblSLjuOtLmcj0q3PDcURNfc0AR8=; b=naLCcToCto6w/Pgu7y6+Ye2fEe7MQPVHIH0wA4pHwZ4DEqyz0XOX8cSO+Owsl9IQ6l9rZZ6MP4XaGKH5EgyX61xo+kW72B/MGG53GVOx68thK7NrGlf+F4Z8rY7BjoZoBr1ASYPYs5DM74Oby8cmhfImFFBVOUUkZnElToNGzaOc99dJW5tItiDLFiKHLL0anXalP/fIXJs+YsVp9W43vFpZM89k54EHo2xs8E2iMOnacp6REMAAIgp0IGJ4TgWQUO+uhj3hmt+jydVpdclnRjf2DG7hDhcXAg4WntgA43l4FxR0k0B6kJP1hCktFNbSu6qRlNIAACwEOBkcWtvgjw== Received: from BYAPR12MB3238.namprd12.prod.outlook.com (2603:10b6:a03:13b::20) by BYAPR12MB4712.namprd12.prod.outlook.com (2603:10b6:a03:9d::14) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.5144.21; Wed, 6 Apr 2022 14:24:36 +0000 Authentication-Results: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=nvidia.com; Received: from MN2PR12MB4192.namprd12.prod.outlook.com (2603:10b6:208:1d5::15) by BYAPR12MB3238.namprd12.prod.outlook.com (2603:10b6:a03:13b::20) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.5123.31; Wed, 6 Apr 2022 14:24:34 +0000 Received: from MN2PR12MB4192.namprd12.prod.outlook.com ([fe80::cdfb:f88e:410b:9374]) by MN2PR12MB4192.namprd12.prod.outlook.com ([fe80::cdfb:f88e:410b:9374%6]) with mapi id 15.20.5144.021; Wed, 6 Apr 2022 14:24:34 +0000 Date: Wed, 6 Apr 2022 11:24:32 -0300 To: Robin Murphy Subject: Re: [PATCH 1/5] iommu: Replace uses of IOMMU_CAP_CACHE_COHERENCY with dev_is_dma_coherent() Message-ID: <20220406142432.GF2120790@nvidia.com> References: <1-v1-ef02c60ddb76+12ca2-intel_no_snoop_jgg@nvidia.com> Content-Disposition: inline In-Reply-To: X-ClientProxiedBy: YT1PR01CA0044.CANPRD01.PROD.OUTLOOK.COM (2603:10b6:b01:2e::13) To MN2PR12MB4192.namprd12.prod.outlook.com (2603:10b6:208:1d5::15) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: 1d8ec298-b8a2-45ff-7223-08da17d92c48 X-MS-TrafficTypeDiagnostic: BYAPR12MB3238:EE_|BYAPR12MB4712:EE_ X-Microsoft-Antispam-PRVS: X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:255.255.255.255; CTRY:; LANG:en; SCL:1; SRV:; IPV:NLI; SFV:NSPM; H:BYAPR12MB3238.namprd12.prod.outlook.com; PTR:; CAT:NONE; SFS:(13230001)(4636009)(366004)(7416002)(8936002)(5660300002)(2906002)(4326008)(8676002)(38100700002)(66476007)(33656002)(86362001)(36756003)(6486002)(508600001)(66556008)(66946007)(6916009)(54906003)(316002)(1076003)(2616005)(6506007)(53546011)(186003)(6512007)(26005); DIR:OUT; SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?j1Rdld5Fo38ZTjZ38MIPGAsmMA5NX1SD3+L7zg2BUvUp8zp8gn1uG7GZ7Cqf?= =?us-ascii?Q?p1p8L1ganek/N/PF3U+4T08mh+V53cV06IHnpXaOs7iFCZ/Qdg2ejWQ+E0ir?= =?us-ascii?Q?A01VuBe9zxrWWChmQxx4RxId1+sNfaLbfFeNR6EcMyT+y4I5civOYXSkb2Av?= =?us-ascii?Q?VEXAh+wNXv8nwUCeE2odpKNg8cxusNS38ob8bnxk6DpMWwDVk0EqiGfvu0sE?= =?us-ascii?Q?swYmaoClsa2c3+HF2Nc/BkNVYWXIm6uRhRU8IG7xwj2nPbCQzx895CXMfMOs?= =?us-ascii?Q?2gyL+Wjlm+KYy9lejPTJscm4QdaaJXP1yO7+Ig9zwJkXJHXU3yWUmGdQcRsM?= =?us-ascii?Q?bwEqrqEl8XAadOWnT52FDuKs3WJ5HkSVNoF9e9yHw9bxpZjM64FWTTXxuczq?= =?us-ascii?Q?kZj3tOLADpCsP0oZgBz9+bzj8cDQn8cqgfFVkgV+Ez7B1Fmy5lqMnRpbqHsC?= =?us-ascii?Q?6HVdOw1Cvn5/6aybMEkgqVBqwOrrJMcYD4jcVPEdpRolmd2K7vDTC1zYTdPa?= =?us-ascii?Q?trtd9g1v+jxw62zYgdyKPpUkiXQgkL7qHqzhwLI9dPcG7grA/jUV/l6xQYS/?= =?us-ascii?Q?m45VA5OebJeGNapmv4FJ4F+fDQEWP1iQr3nN6czi9JyEnWKaE5JtsW1wiKmB?= =?us-ascii?Q?RkHzLAFKJywQnDLI8rJUWl3LjpNpz6/mc3pdItQ8a6b23MUhx2h99W7WMlmZ?= =?us-ascii?Q?ofjCUs2j99hZTvPiiqPFFm5UQUo5mGQ6X8Ui59ENeJoRLhKk/Sb93cd//+Yy?= =?us-ascii?Q?3K5IJK8+cQQ+P3uoRa8vkTp0eivTo6/WeRxLZil5oCQMxIUdu0L+qZ4RFsJi?= =?us-ascii?Q?rp5RbYeNZ0IDvPLcHe9IBw5sTdANsbf2kj4+BBLrqy/5Ke78bwHH/VBWjpL4?= =?us-ascii?Q?BtZHm5k/sVtzqGgCCZaCS4CukhjWX5lrxi9QDlythZz/javtfMt5MXBu2XBM?= =?us-ascii?Q?Tr1S2wPCaev90Q/SfRQjnvsPa4pk1z8IQHrQAQZ9aLiCBeyolZjBBbJzK9YD?= =?us-ascii?Q?y+/KPscj829uDe2go1OXAs+B42V5iDaebBeGDjoBsuzJML+4drpBwWaH7jqt?= =?us-ascii?Q?mEBF2Bykqa6gRuoTNlS/f6FoQpF0e1xiZe9DiRmdtf9Vha7kQ55HtpfVRzBL?= =?us-ascii?Q?oy+LM5GKOV1OI4r9VqLSVPsbGc9uMufyQ89qSn/z0npzPqmn/CPD+9DEanSp?= =?us-ascii?Q?+czvtnsa/2ZaWs39mWjTi0rn0nTfvN0N9MKFZH2l04XkVtS08IJgoOGMDD9y?= =?us-ascii?Q?xbNnXlSNWUzVhFfTvZsgWEYCLUmTho5knPA9POPAQfTWbwao/BIsMsGjvYbe?= =?us-ascii?Q?siozhacB1VGR3473pHktK07LQH915ou6lAa+P3fpnABYNxdex082vKOU7Dg3?= =?us-ascii?Q?/9j2IVvYGL0CzYAY8S2QLQC0KZpUAIiLY2eOipwhYGZjO4tlx3rvopo5rlFX?= =?us-ascii?Q?XFLC7QiPAqMwiPYm/S2jeKNNWtBrAoo6hoderQALU6DYAp8YtT4Zo0yS6mEL?= =?us-ascii?Q?Imv9KbJfHBj21ol8woLA1nBtwzhO2RUXvBL2rkeIE9c2Jv1Xy24Qu6pagkn6?= =?us-ascii?Q?4aCL0GdlpPs8Hc0syEJIChGyQ2H+t6KAzNbdhGIYZT4vwfV2wX7eWZ+1HjK0?= =?us-ascii?Q?jfzIypDQEIAImv08bfBZjEMZzQKY5wxQGx9HZeGeFlTPtDLPMZF3RdQ8svmF?= =?us-ascii?Q?SGxg9vG6mGsnxmqKDZ3WOz0LjqwmeyztO3JmebxMWL6u+EFE9TvuYKImEhhG?= =?us-ascii?Q?7joljw21kA=3D=3D?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: 1d8ec298-b8a2-45ff-7223-08da17d92c48 X-MS-Exchange-CrossTenant-AuthSource: MN2PR12MB4192.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 06 Apr 2022 14:24:34.5883 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: to0YNbI5NCs1iQcSoMToWSaVLgDn9KA2Utie6CPdXXB5PeX8CcZNQ+XkDmn9wvMQ X-MS-Exchange-Transport-CrossTenantHeadersStamped: BYAPR12MB4712 Cc: Nelson Escobar , "Michael S. Tsirkin" , Jason Wang , virtualization@lists.linux-foundation.org, Will Deacon , Christoph Hellwig , linux-s390@vger.kernel.org, kvm@vger.kernel.org, linux-rdma@vger.kernel.org, Gerald Schaefer , "Tian, Kevin" , linux-arm-msm@vger.kernel.org, Alex Williamson , linux-arm-kernel@lists.infradead.org, netdev@vger.kernel.org, Cornelia Huck , iommu@lists.linux-foundation.org, Christian Benvenuti , David Woodhouse 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: , From: Jason Gunthorpe via iommu Reply-To: Jason Gunthorpe Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: iommu-bounces@lists.linux-foundation.org Sender: "iommu" On Wed, Apr 06, 2022 at 02:56:56PM +0100, Robin Murphy wrote: > On 2022-04-05 17:16, Jason Gunthorpe wrote: > > vdpa and usnic are trying to test if IOMMU_CACHE is supported. The correct > > way to do this is via dev_is_dma_coherent() > > Not necessarily... > > Disregarding the complete disaster of PCIe No Snoop on Arm-Based systems, > there's the more interesting effectively-opposite scenario where an SMMU > bridges non-coherent devices to a coherent interconnect. It's not something > we take advantage of yet in Linux, and it can only be properly described in > ACPI, but there do exist situations where IOMMU_CACHE is capable of making > the device's traffic snoop, but dev_is_dma_coherent() - and > device_get_dma_attr() for external users - would still say non-coherent > because they can't assume that the SMMU is enabled and programmed in just > the right way. Oh, I didn't know about device_get_dma_attr().. Considering your future issue, maybe this: /* * true if the given domain supports IOMMU_CACHE and when dev is attached to * that domain it will have coherent DMA and require no cache * maintenance when IOMMU_CACHE is used. */ bool iommu_domain_supports_coherent_dma(struct iommu_domain *domain, struct device *dev) { return device_get_dma_attr(dev) == DEV_DMA_COHERENT; } ? In future it could become a domain op and the SMMU driver could figure out the situation you described? Jason _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu 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 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 smtp.lore.kernel.org (Postfix) with ESMTPS id 5D761C433EF for ; Wed, 6 Apr 2022 14:44:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:In-Reply-To:References: Message-ID:Subject:Cc: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=Mii1W/GswSep6peXgk+RaXQzzo2DbpmzalxRZsLcVt8=; b=CCqfrREzfZg7Z3 Y4D37eiGhX/zJnoU+K0O3Z9FcrXRkXUZqsf5Bxuv6v8QGe6xikLzFoPOw1TEiy093yAGTfNH7QEvE yEyw/KCBqcfsmUQ1GnYVV5oW4ZZ0/M+Y2pD+GF1hB9tInLC+MlUW/XWj7HraPGbOR3RxPsmxQrg+g /hoJ7dysQZO2SYV9WxPvtQ/Cwlv6ss1prTr8j1Wkar4iOtHOocu0ybjqWMt4KSXAzS+maTcYNr1kH xPuArJ2XB/vZDaqjIWxNWEZKCaPqgfFq5CH2AHpP3Wz6u3BcXyqbgl+S2rAXKTf9XDhS4e0RBk/nA jr4lIeBovQLAO6lFTDSQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1nc6sP-006bhM-2D; Wed, 06 Apr 2022 14:43:17 +0000 Received: from mail-dm3nam07on20619.outbound.protection.outlook.com ([2a01:111:f400:7e83::619] helo=NAM02-DM3-obe.outbound.protection.outlook.com) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1nc6oE-006ZYR-Kz for linux-arm-kernel@lists.infradead.org; Wed, 06 Apr 2022 14:39:00 +0000 ARC-Seal: i=1; a=rsa-sha256; s=arcselector9901; d=microsoft.com; cv=none; b=FPR1uDKmgNXOHJiYi/X0WY+KGSpItskwKY+x+iJfqw/4eNrUCAjgjrQIgdKZc7HKcYrRIqfWHFngZruQst4FKWuKTmsIJJZ9JTEmmM45LL02Ko6h6XCpSfOzcQxZFjF8LOp3jV4VFIHn+qh6SkM01p5HfMrU7Mz9XN+dKqGo53PiZEyUBeGP0i7P9VJ69UfZouW3qFxxtKoTsWRNLfd2l0Rv/XSnV9i3P3ykh4dVxQObQHWSUPLlu9YLCpyFtXFqL5rlAG3axksNE2BqQRIoOo8GgPraKafVXwazeh7H86GvR5omtf+HLgM3/FCT4CSSxCo4b/t94xCdk7Vv+agYWQ== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com; s=arcselector9901; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-AntiSpam-MessageData-ChunkCount:X-MS-Exchange-AntiSpam-MessageData-0:X-MS-Exchange-AntiSpam-MessageData-1; bh=1uYgX1e2UDd/ai7mblSLjuOtLmcj0q3PDcURNfc0AR8=; b=abgZWDRNWEvadotFNh2t6vzrArNqc4bV/lTwWRR5GilcLjTnr+1EG5orGPWPIdv7i1Qod2kvbfq4fUmFmn4m0kCpKp4Ik8VCIlYkjlvHwQj1CQy1aGe5n6EcTPU1mduwUZwJvtXqRYUq1fvqLPt7aoJcsgZOiZ6f8u5UD4Pk3IPBmguKP/bm3bWVzn4qoR5dB1VIMc84lOuiTjE8wEFxN4ugvF7WVzR/G5eLMdIZb6ZVW455nQ1LbTZ+waDA368mO+0PwSkHMjx0DQnb0TKr6bsID+qFjr0M3M64DiTX9G9fSmkRkbZhyROuKNIuO9jsA3vuO4JK0YysewPRW49PNQ== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass smtp.mailfrom=nvidia.com; dmarc=pass action=none header.from=nvidia.com; dkim=pass header.d=nvidia.com; arc=none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=Nvidia.com; s=selector2; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=1uYgX1e2UDd/ai7mblSLjuOtLmcj0q3PDcURNfc0AR8=; b=naLCcToCto6w/Pgu7y6+Ye2fEe7MQPVHIH0wA4pHwZ4DEqyz0XOX8cSO+Owsl9IQ6l9rZZ6MP4XaGKH5EgyX61xo+kW72B/MGG53GVOx68thK7NrGlf+F4Z8rY7BjoZoBr1ASYPYs5DM74Oby8cmhfImFFBVOUUkZnElToNGzaOc99dJW5tItiDLFiKHLL0anXalP/fIXJs+YsVp9W43vFpZM89k54EHo2xs8E2iMOnacp6REMAAIgp0IGJ4TgWQUO+uhj3hmt+jydVpdclnRjf2DG7hDhcXAg4WntgA43l4FxR0k0B6kJP1hCktFNbSu6qRlNIAACwEOBkcWtvgjw== Received: from BYAPR12MB3238.namprd12.prod.outlook.com (2603:10b6:a03:13b::20) by BYAPR12MB4712.namprd12.prod.outlook.com (2603:10b6:a03:9d::14) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.5144.21; Wed, 6 Apr 2022 14:24:36 +0000 Authentication-Results: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=nvidia.com; Received: from MN2PR12MB4192.namprd12.prod.outlook.com (2603:10b6:208:1d5::15) by BYAPR12MB3238.namprd12.prod.outlook.com (2603:10b6:a03:13b::20) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.5123.31; Wed, 6 Apr 2022 14:24:34 +0000 Received: from MN2PR12MB4192.namprd12.prod.outlook.com ([fe80::cdfb:f88e:410b:9374]) by MN2PR12MB4192.namprd12.prod.outlook.com ([fe80::cdfb:f88e:410b:9374%6]) with mapi id 15.20.5144.021; Wed, 6 Apr 2022 14:24:34 +0000 Date: Wed, 6 Apr 2022 11:24:32 -0300 From: Jason Gunthorpe To: Robin Murphy Cc: Alex Williamson , Lu Baolu , Christian Benvenuti , Cornelia Huck , David Woodhouse , Gerald Schaefer , iommu@lists.linux-foundation.org, Jason Wang , Joerg Roedel , kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-arm-msm@vger.kernel.org, linux-rdma@vger.kernel.org, linux-s390@vger.kernel.org, Matthew Rosato , "Michael S. Tsirkin" , Nelson Escobar , netdev@vger.kernel.org, Rob Clark , Suravee Suthikulpanit , virtualization@lists.linux-foundation.org, Will Deacon , Christoph Hellwig , "Tian, Kevin" Subject: Re: [PATCH 1/5] iommu: Replace uses of IOMMU_CAP_CACHE_COHERENCY with dev_is_dma_coherent() Message-ID: <20220406142432.GF2120790@nvidia.com> References: <1-v1-ef02c60ddb76+12ca2-intel_no_snoop_jgg@nvidia.com> Content-Disposition: inline In-Reply-To: X-ClientProxiedBy: YT1PR01CA0044.CANPRD01.PROD.OUTLOOK.COM (2603:10b6:b01:2e::13) To MN2PR12MB4192.namprd12.prod.outlook.com (2603:10b6:208:1d5::15) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: 1d8ec298-b8a2-45ff-7223-08da17d92c48 X-MS-TrafficTypeDiagnostic: BYAPR12MB3238:EE_|BYAPR12MB4712:EE_ X-Microsoft-Antispam-PRVS: X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:255.255.255.255; CTRY:; LANG:en; SCL:1; SRV:; IPV:NLI; SFV:NSPM; H:BYAPR12MB3238.namprd12.prod.outlook.com; PTR:; CAT:NONE; SFS:(13230001)(4636009)(366004)(7416002)(8936002)(5660300002)(2906002)(4326008)(8676002)(38100700002)(66476007)(33656002)(86362001)(36756003)(6486002)(508600001)(66556008)(66946007)(6916009)(54906003)(316002)(1076003)(2616005)(6506007)(53546011)(186003)(6512007)(26005); DIR:OUT; SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?j1Rdld5Fo38ZTjZ38MIPGAsmMA5NX1SD3+L7zg2BUvUp8zp8gn1uG7GZ7Cqf?= =?us-ascii?Q?p1p8L1ganek/N/PF3U+4T08mh+V53cV06IHnpXaOs7iFCZ/Qdg2ejWQ+E0ir?= =?us-ascii?Q?A01VuBe9zxrWWChmQxx4RxId1+sNfaLbfFeNR6EcMyT+y4I5civOYXSkb2Av?= =?us-ascii?Q?VEXAh+wNXv8nwUCeE2odpKNg8cxusNS38ob8bnxk6DpMWwDVk0EqiGfvu0sE?= =?us-ascii?Q?swYmaoClsa2c3+HF2Nc/BkNVYWXIm6uRhRU8IG7xwj2nPbCQzx895CXMfMOs?= =?us-ascii?Q?2gyL+Wjlm+KYy9lejPTJscm4QdaaJXP1yO7+Ig9zwJkXJHXU3yWUmGdQcRsM?= =?us-ascii?Q?bwEqrqEl8XAadOWnT52FDuKs3WJ5HkSVNoF9e9yHw9bxpZjM64FWTTXxuczq?= =?us-ascii?Q?kZj3tOLADpCsP0oZgBz9+bzj8cDQn8cqgfFVkgV+Ez7B1Fmy5lqMnRpbqHsC?= =?us-ascii?Q?6HVdOw1Cvn5/6aybMEkgqVBqwOrrJMcYD4jcVPEdpRolmd2K7vDTC1zYTdPa?= =?us-ascii?Q?trtd9g1v+jxw62zYgdyKPpUkiXQgkL7qHqzhwLI9dPcG7grA/jUV/l6xQYS/?= =?us-ascii?Q?m45VA5OebJeGNapmv4FJ4F+fDQEWP1iQr3nN6czi9JyEnWKaE5JtsW1wiKmB?= =?us-ascii?Q?RkHzLAFKJywQnDLI8rJUWl3LjpNpz6/mc3pdItQ8a6b23MUhx2h99W7WMlmZ?= =?us-ascii?Q?ofjCUs2j99hZTvPiiqPFFm5UQUo5mGQ6X8Ui59ENeJoRLhKk/Sb93cd//+Yy?= =?us-ascii?Q?3K5IJK8+cQQ+P3uoRa8vkTp0eivTo6/WeRxLZil5oCQMxIUdu0L+qZ4RFsJi?= =?us-ascii?Q?rp5RbYeNZ0IDvPLcHe9IBw5sTdANsbf2kj4+BBLrqy/5Ke78bwHH/VBWjpL4?= =?us-ascii?Q?BtZHm5k/sVtzqGgCCZaCS4CukhjWX5lrxi9QDlythZz/javtfMt5MXBu2XBM?= =?us-ascii?Q?Tr1S2wPCaev90Q/SfRQjnvsPa4pk1z8IQHrQAQZ9aLiCBeyolZjBBbJzK9YD?= =?us-ascii?Q?y+/KPscj829uDe2go1OXAs+B42V5iDaebBeGDjoBsuzJML+4drpBwWaH7jqt?= =?us-ascii?Q?mEBF2Bykqa6gRuoTNlS/f6FoQpF0e1xiZe9DiRmdtf9Vha7kQ55HtpfVRzBL?= =?us-ascii?Q?oy+LM5GKOV1OI4r9VqLSVPsbGc9uMufyQ89qSn/z0npzPqmn/CPD+9DEanSp?= =?us-ascii?Q?+czvtnsa/2ZaWs39mWjTi0rn0nTfvN0N9MKFZH2l04XkVtS08IJgoOGMDD9y?= =?us-ascii?Q?xbNnXlSNWUzVhFfTvZsgWEYCLUmTho5knPA9POPAQfTWbwao/BIsMsGjvYbe?= =?us-ascii?Q?siozhacB1VGR3473pHktK07LQH915ou6lAa+P3fpnABYNxdex082vKOU7Dg3?= =?us-ascii?Q?/9j2IVvYGL0CzYAY8S2QLQC0KZpUAIiLY2eOipwhYGZjO4tlx3rvopo5rlFX?= =?us-ascii?Q?XFLC7QiPAqMwiPYm/S2jeKNNWtBrAoo6hoderQALU6DYAp8YtT4Zo0yS6mEL?= =?us-ascii?Q?Imv9KbJfHBj21ol8woLA1nBtwzhO2RUXvBL2rkeIE9c2Jv1Xy24Qu6pagkn6?= =?us-ascii?Q?4aCL0GdlpPs8Hc0syEJIChGyQ2H+t6KAzNbdhGIYZT4vwfV2wX7eWZ+1HjK0?= =?us-ascii?Q?jfzIypDQEIAImv08bfBZjEMZzQKY5wxQGx9HZeGeFlTPtDLPMZF3RdQ8svmF?= =?us-ascii?Q?SGxg9vG6mGsnxmqKDZ3WOz0LjqwmeyztO3JmebxMWL6u+EFE9TvuYKImEhhG?= =?us-ascii?Q?7joljw21kA=3D=3D?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: 1d8ec298-b8a2-45ff-7223-08da17d92c48 X-MS-Exchange-CrossTenant-AuthSource: MN2PR12MB4192.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 06 Apr 2022 14:24:34.5883 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: to0YNbI5NCs1iQcSoMToWSaVLgDn9KA2Utie6CPdXXB5PeX8CcZNQ+XkDmn9wvMQ X-MS-Exchange-Transport-CrossTenantHeadersStamped: BYAPR12MB4712 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220406_073858_742045_A4242C77 X-CRM114-Status: GOOD ( 14.88 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , 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, Apr 06, 2022 at 02:56:56PM +0100, Robin Murphy wrote: > On 2022-04-05 17:16, Jason Gunthorpe wrote: > > vdpa and usnic are trying to test if IOMMU_CACHE is supported. The correct > > way to do this is via dev_is_dma_coherent() > > Not necessarily... > > Disregarding the complete disaster of PCIe No Snoop on Arm-Based systems, > there's the more interesting effectively-opposite scenario where an SMMU > bridges non-coherent devices to a coherent interconnect. It's not something > we take advantage of yet in Linux, and it can only be properly described in > ACPI, but there do exist situations where IOMMU_CACHE is capable of making > the device's traffic snoop, but dev_is_dma_coherent() - and > device_get_dma_attr() for external users - would still say non-coherent > because they can't assume that the SMMU is enabled and programmed in just > the right way. Oh, I didn't know about device_get_dma_attr().. Considering your future issue, maybe this: /* * true if the given domain supports IOMMU_CACHE and when dev is attached to * that domain it will have coherent DMA and require no cache * maintenance when IOMMU_CACHE is used. */ bool iommu_domain_supports_coherent_dma(struct iommu_domain *domain, struct device *dev) { return device_get_dma_attr(dev) == DEV_DMA_COHERENT; } ? In future it could become a domain op and the SMMU driver could figure out the situation you described? Jason _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel 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 AD0DEC433EF for ; Wed, 6 Apr 2022 16:58:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238553AbiDFRAy (ORCPT ); Wed, 6 Apr 2022 13:00:54 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51012 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238421AbiDFRAt (ORCPT ); Wed, 6 Apr 2022 13:00:49 -0400 Received: from NAM02-BN1-obe.outbound.protection.outlook.com (mail-bn1nam07on2050.outbound.protection.outlook.com [40.107.212.50]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 767DA46E606; Wed, 6 Apr 2022 07:24:38 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; s=arcselector9901; d=microsoft.com; cv=none; b=FPR1uDKmgNXOHJiYi/X0WY+KGSpItskwKY+x+iJfqw/4eNrUCAjgjrQIgdKZc7HKcYrRIqfWHFngZruQst4FKWuKTmsIJJZ9JTEmmM45LL02Ko6h6XCpSfOzcQxZFjF8LOp3jV4VFIHn+qh6SkM01p5HfMrU7Mz9XN+dKqGo53PiZEyUBeGP0i7P9VJ69UfZouW3qFxxtKoTsWRNLfd2l0Rv/XSnV9i3P3ykh4dVxQObQHWSUPLlu9YLCpyFtXFqL5rlAG3axksNE2BqQRIoOo8GgPraKafVXwazeh7H86GvR5omtf+HLgM3/FCT4CSSxCo4b/t94xCdk7Vv+agYWQ== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com; s=arcselector9901; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-AntiSpam-MessageData-ChunkCount:X-MS-Exchange-AntiSpam-MessageData-0:X-MS-Exchange-AntiSpam-MessageData-1; bh=1uYgX1e2UDd/ai7mblSLjuOtLmcj0q3PDcURNfc0AR8=; b=abgZWDRNWEvadotFNh2t6vzrArNqc4bV/lTwWRR5GilcLjTnr+1EG5orGPWPIdv7i1Qod2kvbfq4fUmFmn4m0kCpKp4Ik8VCIlYkjlvHwQj1CQy1aGe5n6EcTPU1mduwUZwJvtXqRYUq1fvqLPt7aoJcsgZOiZ6f8u5UD4Pk3IPBmguKP/bm3bWVzn4qoR5dB1VIMc84lOuiTjE8wEFxN4ugvF7WVzR/G5eLMdIZb6ZVW455nQ1LbTZ+waDA368mO+0PwSkHMjx0DQnb0TKr6bsID+qFjr0M3M64DiTX9G9fSmkRkbZhyROuKNIuO9jsA3vuO4JK0YysewPRW49PNQ== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass smtp.mailfrom=nvidia.com; dmarc=pass action=none header.from=nvidia.com; dkim=pass header.d=nvidia.com; arc=none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=Nvidia.com; s=selector2; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=1uYgX1e2UDd/ai7mblSLjuOtLmcj0q3PDcURNfc0AR8=; b=naLCcToCto6w/Pgu7y6+Ye2fEe7MQPVHIH0wA4pHwZ4DEqyz0XOX8cSO+Owsl9IQ6l9rZZ6MP4XaGKH5EgyX61xo+kW72B/MGG53GVOx68thK7NrGlf+F4Z8rY7BjoZoBr1ASYPYs5DM74Oby8cmhfImFFBVOUUkZnElToNGzaOc99dJW5tItiDLFiKHLL0anXalP/fIXJs+YsVp9W43vFpZM89k54EHo2xs8E2iMOnacp6REMAAIgp0IGJ4TgWQUO+uhj3hmt+jydVpdclnRjf2DG7hDhcXAg4WntgA43l4FxR0k0B6kJP1hCktFNbSu6qRlNIAACwEOBkcWtvgjw== Received: from BYAPR12MB3238.namprd12.prod.outlook.com (2603:10b6:a03:13b::20) by BYAPR12MB4712.namprd12.prod.outlook.com (2603:10b6:a03:9d::14) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.5144.21; Wed, 6 Apr 2022 14:24:36 +0000 Authentication-Results: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=nvidia.com; Received: from MN2PR12MB4192.namprd12.prod.outlook.com (2603:10b6:208:1d5::15) by BYAPR12MB3238.namprd12.prod.outlook.com (2603:10b6:a03:13b::20) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.5123.31; Wed, 6 Apr 2022 14:24:34 +0000 Received: from MN2PR12MB4192.namprd12.prod.outlook.com ([fe80::cdfb:f88e:410b:9374]) by MN2PR12MB4192.namprd12.prod.outlook.com ([fe80::cdfb:f88e:410b:9374%6]) with mapi id 15.20.5144.021; Wed, 6 Apr 2022 14:24:34 +0000 Date: Wed, 6 Apr 2022 11:24:32 -0300 From: Jason Gunthorpe To: Robin Murphy Cc: Alex Williamson , Lu Baolu , Christian Benvenuti , Cornelia Huck , David Woodhouse , Gerald Schaefer , iommu@lists.linux-foundation.org, Jason Wang , Joerg Roedel , kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-arm-msm@vger.kernel.org, linux-rdma@vger.kernel.org, linux-s390@vger.kernel.org, Matthew Rosato , "Michael S. Tsirkin" , Nelson Escobar , netdev@vger.kernel.org, Rob Clark , Suravee Suthikulpanit , virtualization@lists.linux-foundation.org, Will Deacon , Christoph Hellwig , "Tian, Kevin" Subject: Re: [PATCH 1/5] iommu: Replace uses of IOMMU_CAP_CACHE_COHERENCY with dev_is_dma_coherent() Message-ID: <20220406142432.GF2120790@nvidia.com> References: <1-v1-ef02c60ddb76+12ca2-intel_no_snoop_jgg@nvidia.com> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-ClientProxiedBy: YT1PR01CA0044.CANPRD01.PROD.OUTLOOK.COM (2603:10b6:b01:2e::13) To MN2PR12MB4192.namprd12.prod.outlook.com (2603:10b6:208:1d5::15) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: 1d8ec298-b8a2-45ff-7223-08da17d92c48 X-MS-TrafficTypeDiagnostic: BYAPR12MB3238:EE_|BYAPR12MB4712:EE_ X-Microsoft-Antispam-PRVS: X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:BYAPR12MB3238.namprd12.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230001)(4636009)(366004)(7416002)(8936002)(5660300002)(2906002)(4326008)(8676002)(38100700002)(66476007)(33656002)(86362001)(36756003)(6486002)(508600001)(66556008)(66946007)(6916009)(54906003)(316002)(1076003)(2616005)(6506007)(53546011)(186003)(6512007)(26005);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?j1Rdld5Fo38ZTjZ38MIPGAsmMA5NX1SD3+L7zg2BUvUp8zp8gn1uG7GZ7Cqf?= =?us-ascii?Q?p1p8L1ganek/N/PF3U+4T08mh+V53cV06IHnpXaOs7iFCZ/Qdg2ejWQ+E0ir?= =?us-ascii?Q?A01VuBe9zxrWWChmQxx4RxId1+sNfaLbfFeNR6EcMyT+y4I5civOYXSkb2Av?= =?us-ascii?Q?VEXAh+wNXv8nwUCeE2odpKNg8cxusNS38ob8bnxk6DpMWwDVk0EqiGfvu0sE?= =?us-ascii?Q?swYmaoClsa2c3+HF2Nc/BkNVYWXIm6uRhRU8IG7xwj2nPbCQzx895CXMfMOs?= =?us-ascii?Q?2gyL+Wjlm+KYy9lejPTJscm4QdaaJXP1yO7+Ig9zwJkXJHXU3yWUmGdQcRsM?= =?us-ascii?Q?bwEqrqEl8XAadOWnT52FDuKs3WJ5HkSVNoF9e9yHw9bxpZjM64FWTTXxuczq?= =?us-ascii?Q?kZj3tOLADpCsP0oZgBz9+bzj8cDQn8cqgfFVkgV+Ez7B1Fmy5lqMnRpbqHsC?= =?us-ascii?Q?6HVdOw1Cvn5/6aybMEkgqVBqwOrrJMcYD4jcVPEdpRolmd2K7vDTC1zYTdPa?= =?us-ascii?Q?trtd9g1v+jxw62zYgdyKPpUkiXQgkL7qHqzhwLI9dPcG7grA/jUV/l6xQYS/?= =?us-ascii?Q?m45VA5OebJeGNapmv4FJ4F+fDQEWP1iQr3nN6czi9JyEnWKaE5JtsW1wiKmB?= =?us-ascii?Q?RkHzLAFKJywQnDLI8rJUWl3LjpNpz6/mc3pdItQ8a6b23MUhx2h99W7WMlmZ?= =?us-ascii?Q?ofjCUs2j99hZTvPiiqPFFm5UQUo5mGQ6X8Ui59ENeJoRLhKk/Sb93cd//+Yy?= =?us-ascii?Q?3K5IJK8+cQQ+P3uoRa8vkTp0eivTo6/WeRxLZil5oCQMxIUdu0L+qZ4RFsJi?= =?us-ascii?Q?rp5RbYeNZ0IDvPLcHe9IBw5sTdANsbf2kj4+BBLrqy/5Ke78bwHH/VBWjpL4?= =?us-ascii?Q?BtZHm5k/sVtzqGgCCZaCS4CukhjWX5lrxi9QDlythZz/javtfMt5MXBu2XBM?= =?us-ascii?Q?Tr1S2wPCaev90Q/SfRQjnvsPa4pk1z8IQHrQAQZ9aLiCBeyolZjBBbJzK9YD?= =?us-ascii?Q?y+/KPscj829uDe2go1OXAs+B42V5iDaebBeGDjoBsuzJML+4drpBwWaH7jqt?= =?us-ascii?Q?mEBF2Bykqa6gRuoTNlS/f6FoQpF0e1xiZe9DiRmdtf9Vha7kQ55HtpfVRzBL?= =?us-ascii?Q?oy+LM5GKOV1OI4r9VqLSVPsbGc9uMufyQ89qSn/z0npzPqmn/CPD+9DEanSp?= =?us-ascii?Q?+czvtnsa/2ZaWs39mWjTi0rn0nTfvN0N9MKFZH2l04XkVtS08IJgoOGMDD9y?= =?us-ascii?Q?xbNnXlSNWUzVhFfTvZsgWEYCLUmTho5knPA9POPAQfTWbwao/BIsMsGjvYbe?= =?us-ascii?Q?siozhacB1VGR3473pHktK07LQH915ou6lAa+P3fpnABYNxdex082vKOU7Dg3?= =?us-ascii?Q?/9j2IVvYGL0CzYAY8S2QLQC0KZpUAIiLY2eOipwhYGZjO4tlx3rvopo5rlFX?= =?us-ascii?Q?XFLC7QiPAqMwiPYm/S2jeKNNWtBrAoo6hoderQALU6DYAp8YtT4Zo0yS6mEL?= =?us-ascii?Q?Imv9KbJfHBj21ol8woLA1nBtwzhO2RUXvBL2rkeIE9c2Jv1Xy24Qu6pagkn6?= =?us-ascii?Q?4aCL0GdlpPs8Hc0syEJIChGyQ2H+t6KAzNbdhGIYZT4vwfV2wX7eWZ+1HjK0?= =?us-ascii?Q?jfzIypDQEIAImv08bfBZjEMZzQKY5wxQGx9HZeGeFlTPtDLPMZF3RdQ8svmF?= =?us-ascii?Q?SGxg9vG6mGsnxmqKDZ3WOz0LjqwmeyztO3JmebxMWL6u+EFE9TvuYKImEhhG?= =?us-ascii?Q?7joljw21kA=3D=3D?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: 1d8ec298-b8a2-45ff-7223-08da17d92c48 X-MS-Exchange-CrossTenant-AuthSource: MN2PR12MB4192.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 06 Apr 2022 14:24:34.5883 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: to0YNbI5NCs1iQcSoMToWSaVLgDn9KA2Utie6CPdXXB5PeX8CcZNQ+XkDmn9wvMQ X-MS-Exchange-Transport-CrossTenantHeadersStamped: BYAPR12MB4712 Precedence: bulk List-ID: X-Mailing-List: linux-arm-msm@vger.kernel.org On Wed, Apr 06, 2022 at 02:56:56PM +0100, Robin Murphy wrote: > On 2022-04-05 17:16, Jason Gunthorpe wrote: > > vdpa and usnic are trying to test if IOMMU_CACHE is supported. The correct > > way to do this is via dev_is_dma_coherent() > > Not necessarily... > > Disregarding the complete disaster of PCIe No Snoop on Arm-Based systems, > there's the more interesting effectively-opposite scenario where an SMMU > bridges non-coherent devices to a coherent interconnect. It's not something > we take advantage of yet in Linux, and it can only be properly described in > ACPI, but there do exist situations where IOMMU_CACHE is capable of making > the device's traffic snoop, but dev_is_dma_coherent() - and > device_get_dma_attr() for external users - would still say non-coherent > because they can't assume that the SMMU is enabled and programmed in just > the right way. Oh, I didn't know about device_get_dma_attr().. Considering your future issue, maybe this: /* * true if the given domain supports IOMMU_CACHE and when dev is attached to * that domain it will have coherent DMA and require no cache * maintenance when IOMMU_CACHE is used. */ bool iommu_domain_supports_coherent_dma(struct iommu_domain *domain, struct device *dev) { return device_get_dma_attr(dev) == DEV_DMA_COHERENT; } ? In future it could become a domain op and the SMMU driver could figure out the situation you described? Jason