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=-5.2 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 1AD7BC2D0A3 for ; Tue, 3 Nov 2020 09:52:22 +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 698E92080C for ; Tue, 3 Nov 2020 09:52:21 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 698E92080C Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=8bytes.org 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 ED92286C80; Tue, 3 Nov 2020 09:52:20 +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 YBLjdfgqVs9H; Tue, 3 Nov 2020 09:52:18 +0000 (UTC) Received: from lists.linuxfoundation.org (lf-lists.osuosl.org [140.211.9.56]) by whitealder.osuosl.org (Postfix) with ESMTP id 595ED86C5B; Tue, 3 Nov 2020 09:52:18 +0000 (UTC) Received: from lf-lists.osuosl.org (localhost [127.0.0.1]) by lists.linuxfoundation.org (Postfix) with ESMTP id 4ACADC08A1; Tue, 3 Nov 2020 09:52:18 +0000 (UTC) Received: from fraxinus.osuosl.org (smtp4.osuosl.org [140.211.166.137]) by lists.linuxfoundation.org (Postfix) with ESMTP id 9434EC0889 for ; Tue, 3 Nov 2020 09:52:16 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by fraxinus.osuosl.org (Postfix) with ESMTP id 77BF785FEB for ; Tue, 3 Nov 2020 09:52:16 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from fraxinus.osuosl.org ([127.0.0.1]) by localhost (.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id Epttr2EHWanr for ; Tue, 3 Nov 2020 09:52:15 +0000 (UTC) X-Greylist: from auto-whitelisted by SQLgrey-1.7.6 Received: from theia.8bytes.org (8bytes.org [81.169.241.247]) by fraxinus.osuosl.org (Postfix) with ESMTPS id 2FB1385FBA for ; Tue, 3 Nov 2020 09:52:15 +0000 (UTC) Received: by theia.8bytes.org (Postfix, from userid 1000) id 6BEAF3D9; Tue, 3 Nov 2020 10:52:12 +0100 (CET) Date: Tue, 3 Nov 2020 10:52:09 +0100 From: "joro@8bytes.org" To: "Tian, Kevin" Subject: Re: (proposal) RE: [PATCH v7 00/16] vfio: expose virtual Shared Virtual Addressing to VMs Message-ID: <20201103095208.GA22888@8bytes.org> References: MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Cc: "jean-philippe@linaro.org" , "Raj, Ashok" , "kvm@vger.kernel.org" , "iommu@lists.linux-foundation.org" , "stefanha@gmail.com" , Jason Wang , "Michael S. Tsirkin" , "Sun, Yi Y" , "alex.williamson@redhat.com" , Jason Gunthorpe , "Wu, Hao" , "Tian, Jun J" 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 Mon, Oct 12, 2020 at 08:38:54AM +0000, Tian, Kevin wrote: > > From: Jason Wang > > Jason suggest something like /dev/sva. There will be a lot of other > > subsystems that could benefit from this (e.g vDPA). Honestly, I fail to see the benefit of offloading these IOMMU specific setup tasks to user-space. The ways PASID and the device partitioning it allows are used are very device specific. A GPU will be partitioned completly different than a network card. So the device drivers should use the (v)SVA APIs to setup the partitioning in a way which makes sense for the device. And VFIO is of course a user by itself, as it allows assigning device partitions to guests. Or even allow assigning complete devices and allow the guests to partition it themselfes. So having said this, what is the benefit of exposing those SVA internals to user-space? Regards, Joerg _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu