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_2 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 34E6DC43461 for ; Wed, 16 Sep 2020 23:09:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D6BF622207 for ; Wed, 16 Sep 2020 23:09:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726419AbgIPXJF (ORCPT ); Wed, 16 Sep 2020 19:09:05 -0400 Received: from mga06.intel.com ([134.134.136.31]:47633 "EHLO mga06.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726311AbgIPXJF (ORCPT ); Wed, 16 Sep 2020 19:09:05 -0400 IronPort-SDR: G13EVxgrWiMUJEvRX1ETlQzgt6Rw2zDqEBfREMZ8mLaSlOku4seoE5FM4jbulolTfVH0JTdA6L zvGyrI+UFPag== X-IronPort-AV: E=McAfee;i="6000,8403,9746"; a="221136274" X-IronPort-AV: E=Sophos;i="5.76,434,1592895600"; d="scan'208";a="221136274" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga004.jf.intel.com ([10.7.209.38]) by orsmga104.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 16 Sep 2020 16:09:04 -0700 IronPort-SDR: ciXVM4r79l01GczmidIOUSxSTwcXHW230qN0CHY8Ys5imcKc7r+Q3pzICMmWls07BPPAdtV2ag LRtHNHKL76EQ== X-IronPort-AV: E=Sophos;i="5.76,434,1592895600"; d="scan'208";a="452047379" Received: from jpan9-mobl2.amr.corp.intel.com (HELO localhost) ([10.213.174.80]) by orsmga004-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 16 Sep 2020 16:09:03 -0700 Date: Wed, 16 Sep 2020 16:09:01 -0700 From: "Jacob Pan (Jun)" To: Jason Gunthorpe Cc: "Raj, Ashok" , Alex Williamson , Jean-Philippe Brucker , Jason Wang , Liu Yi L , , , , , , , , , , , , "Michael S. Tsirkin" , , jacob.jun.pan@intel.com Subject: Re: [PATCH v7 00/16] vfio: expose virtual Shared Virtual Addressing to VMs Message-ID: <20200916160901.000046ec@intel.com> In-Reply-To: <20200916183841.GI6199@nvidia.com> References: <20200915113341.GW904879@nvidia.com> <20200915181154.GA70770@otc-nc-03> <20200915184510.GB1573713@nvidia.com> <20200915150851.76436ca1@jacob-builder> <20200915235126.GK1573713@nvidia.com> <20200915171319.00003f59@linux.intel.com> <20200916150754.GE6199@nvidia.com> <20200916163343.GA76252@otc-nc-03> <20200916170113.GD3699@nvidia.com> <20200916112110.000024ee@intel.com> <20200916183841.GI6199@nvidia.com> Organization: OTC X-Mailer: Claws Mail 3.17.3 (GTK+ 2.24.32; i686-w64-mingw32) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org Hi Jason, On Wed, 16 Sep 2020 15:38:41 -0300, Jason Gunthorpe wrote: > On Wed, Sep 16, 2020 at 11:21:10AM -0700, Jacob Pan (Jun) wrote: > > Hi Jason, > > On Wed, 16 Sep 2020 14:01:13 -0300, Jason Gunthorpe > > wrote: > > > > > On Wed, Sep 16, 2020 at 09:33:43AM -0700, Raj, Ashok wrote: > > > > On Wed, Sep 16, 2020 at 12:07:54PM -0300, Jason Gunthorpe > > > > wrote: > > > > > On Tue, Sep 15, 2020 at 05:22:26PM -0700, Jacob Pan (Jun) > > > > > wrote: > > > > > > > If user space wants to bind page tables, create the PASID > > > > > > > with /dev/sva, use ioctls there to setup the page table > > > > > > > the way it wants, then pass the now configured PASID to a > > > > > > > driver that can use it. > > > > > > > > > > > > Are we talking about bare metal SVA? > > > > > > > > > > What a weird term. > > > > > > > > Glad you noticed it at v7 :-) > > > > > > > > Any suggestions on something less weird than > > > > Shared Virtual Addressing? There is a reason why we moved from > > > > SVM to SVA. > > > > > > SVA is fine, what is "bare metal" supposed to mean? > > > > > What I meant here is sharing virtual address between DMA and host > > process. This requires devices perform DMA request with PASID and > > use IOMMU first level/stage 1 page tables. > > This can be further divided into 1) user SVA 2) supervisor SVA > > (sharing init_mm) > > > > My point is that /dev/sva is not useful here since the driver can > > perform PASID allocation while doing SVA bind. > > No, you are thinking too small. > > Look at VDPA, it has a SVA uAPI. Some HW might use PASID for the SVA. > Could you point to me the SVA UAPI? I couldn't find it in the mainline. Seems VDPA uses VHOST interface? > When VDPA is used by DPDK it makes sense that the PASID will be SVA > and 1:1 with the mm_struct. > I still don't see why bare metal DPDK needs to get a handle of the PASID. Perhaps the SVA patch would explain. Or are you talking about vDPA DPDK process that is used to support virtio-net-pmd in the guest? > When VDPA is used by qemu it makes sense that the PASID will be an > arbitary IOVA map constructed to be 1:1 with the guest vCPU physical > map. /dev/sva allows a single uAPI to do this kind of setup, and qemu > can support it while supporting a range of SVA kernel drivers. VDPA > and vfio-mdev are obvious initial targets. > > *BOTH* are needed. > > In general any uAPI for PASID should have the option to use either the > mm_struct SVA PASID *OR* a PASID from /dev/sva. It costs virtually > nothing to implement this in the driver as PASID is just a number, and > gives so much more flexability. > Not really nothing in terms of PASID life cycles. For example, if user uses uacce interface to open an accelerator, it gets an FD_acc. Then it opens /dev/sva to allocate PASID then get another FD_pasid. Then we pass FD_pasid to the driver to bind page tables, perhaps multiple drivers. Now we have to worry about If FD_pasid gets closed before FD_acc(s) closed and all these race conditions. If we do not expose FD_pasid to the user, the teardown is much simpler and streamlined. Following each FD_acc close, PASID unbind is performed. > > Yi can correct me but this set is is about VFIO-PCI, VFIO-mdev will > > be introduced later. > > Last patch is: > > vfio/type1: Add vSVA support for IOMMU-backed mdevs > > So pretty hard to see how this is not about vfio-mdev, at least a > little.. > > Jason Thanks, Jacob