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 gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (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 9BB86EE49A0 for ; Mon, 21 Aug 2023 20:57:18 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 4D26F10E2B2; Mon, 21 Aug 2023 20:57:18 +0000 (UTC) Received: from NAM10-DM6-obe.outbound.protection.outlook.com (mail-dm6nam10on2052.outbound.protection.outlook.com [40.107.93.52]) by gabe.freedesktop.org (Postfix) with ESMTPS id 1DC3510E2B1; Mon, 21 Aug 2023 20:57:17 +0000 (UTC) ARC-Seal: i=1; a=rsa-sha256; s=arcselector9901; d=microsoft.com; cv=none; b=Gge/98u5K4z7SCvSeSzmyJZZubeAik9CKyLK0rzZvlnYuWYfel71BOHmbi5/cx73VV47J7HTcsBsQP2oF6pqdFrvjpbD+vScUYog6aaYBYooSyL1Gy/XNjQHdeQRJU6t9FPHnOKXNpcTYLFXmjtr7C6e36hMS5rsj/mi1HftSQAgsespdkpyd10NfEVO2i6wI5zG6efJnw2f0fTiMb7qLmSnMt2zQ1XoVvHt4ZefKaoLCEBpr/OoDJPK7jyLoN5FxFTT6EQ445/SO+aLWHjafRtVZsBdo94l2/HcB7+GuaZ1OT5Lwf+tj7jw0qhhwsxiZmXMqcl+ioKX7ZYYXEM8lQ== 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=iUfeEyNGWR5pSJ+eBvrAnYp7WviJ49oVkr8VMxMnjX4=; b=SPXfJKhQI0kATp1XpiBybtLnJ8DGlIHZua0kJh0N1zxKa6k9K/rnijJm4431ZcVwyicRJRhSCDwt50KntOQFLZD8nL8pQE89muRtZJEEh2GZGZqnu1u4FZTSFKWZaHpid+WJhAGoCPyFDl76AW+W2HKmUg2rYavs4m/e2mKA5qOadp5SnR4OPsg0K28/0+zP3EGWuGjlRFEFLZu+06QO8Y7Igw02TWRDZ7FGBLsT76TzM8EWc7MyqQmBai2bWlsAqrSsXpd16eglO8grODXuStJcsOyGJn72+/ajjrAvWIH94sKZ5vnoxGOK4AmEZ2JJh8TcoBW3mf77gBv8eQfpZA== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass smtp.mailfrom=amd.com; dmarc=pass action=none header.from=amd.com; dkim=pass header.d=amd.com; arc=none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=amd.com; s=selector1; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=iUfeEyNGWR5pSJ+eBvrAnYp7WviJ49oVkr8VMxMnjX4=; b=qkAVX/kYY85BYoAcg05iMqkW130tjhjBSJeWNHJI4jZnbdPHp0JrWfXJnzDEqeX7InJ/hbsI8NMyvA5AqoleJRFZkRrQfI3QkkxQN6fQ4BPTzJ3AP+KoDi4w+dyyzJo725vAIFeBeA95RJAN86Ko8avrqy5BDHv7cs4auxRgICY= Authentication-Results: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=amd.com; Received: from BN9PR12MB5115.namprd12.prod.outlook.com (2603:10b6:408:118::14) by CYXPR12MB9280.namprd12.prod.outlook.com (2603:10b6:930:e4::5) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.6699.24; Mon, 21 Aug 2023 20:57:14 +0000 Received: from BN9PR12MB5115.namprd12.prod.outlook.com ([fe80::ca28:efb4:a838:58fb]) by BN9PR12MB5115.namprd12.prod.outlook.com ([fe80::ca28:efb4:a838:58fb%4]) with mapi id 15.20.6699.022; Mon, 21 Aug 2023 20:57:14 +0000 Message-ID: Date: Mon, 21 Aug 2023 16:57:12 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.13.0 Content-Language: en-US To: "Zeng, Oak" , Dave Airlie References: <3c125b60-df60-2037-c23f-918734e4973f@amd.com> <7ae5f112-d0e9-cc52-2b22-7265ea435cc2@amd.com> <637ce3f5-a7a9-6a1f-812a-5987211f84f7@amd.com> From: Felix Kuehling Organization: AMD Inc. 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The main unsolved (unsolvable?) problem I ran into was, that >> there is no way to share SVM memory as DMABufs. So there is no good way >> to support applications that expect to share memory in that way. > Great point. I also discussed the dmabuf thing with Mike (cc'ed). dmabuf is a particular technology created specially for the BO driver (and other driver) to share buffer b/t devices. Hmm/system SVM doesn't need this technology: malloc'ed memory by the nature is already shared b/t different devices (in one process) and CPU. We just can simply submit GPU kernel to all devices with malloc'ed memory and let kmd decide the memory placement (such as map in place or migrate). No need of buffer export/import in hmm/system SVM world. I disagree. DMABuf can be used for sharing memory between processes. And it can be used for sharing memory with 3rd-party devices via PCIe P2P (e.g. a Mellanox NIC). You cannot easily do that with malloc'ed memory. POSIX IPC requires that you know that you'll be sharing the memory at allocation time. It adds overhead. And because it's file-backed, it's currently incompatible with migration. And HMM currently doesn't have a solution for P2P. Any access by a different device causes a migration to system memory. Regards,   Felix > > So yes from buffer sharing perspective, the design philosophy is also very different. > > Thanks, > Oak >