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, 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 1EA08C2D0A3 for ; Tue, 3 Nov 2020 09:52:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C1DC821556 for ; Tue, 3 Nov 2020 09:52:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727998AbgKCJwQ (ORCPT ); Tue, 3 Nov 2020 04:52:16 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60102 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726013AbgKCJwQ (ORCPT ); Tue, 3 Nov 2020 04:52:16 -0500 Received: from theia.8bytes.org (8bytes.org [IPv6:2a01:238:4383:600:38bc:a715:4b6d:a889]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3488EC0613D1 for ; Tue, 3 Nov 2020 01:52:16 -0800 (PST) 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" Cc: Jason Wang , "Liu, Yi L" , "alex.williamson@redhat.com" , "eric.auger@redhat.com" , "baolu.lu@linux.intel.com" , "jacob.jun.pan@linux.intel.com" , "Raj, Ashok" , "Tian, Jun J" , "Sun, Yi Y" , "jean-philippe@linaro.org" , "peterx@redhat.com" , "Wu, Hao" , "stefanha@gmail.com" , "iommu@lists.linux-foundation.org" , "kvm@vger.kernel.org" , Jason Gunthorpe , "Michael S. Tsirkin" 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-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org 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