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=-2.2 required=3.0 tests=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 4578FC10DCE for ; Wed, 25 Mar 2020 01:06:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 18F1420724 for ; Wed, 25 Mar 2020 01:06:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727249AbgCYBGL (ORCPT ); Tue, 24 Mar 2020 21:06:11 -0400 Received: from mga01.intel.com ([192.55.52.88]:32038 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727113AbgCYBGK (ORCPT ); Tue, 24 Mar 2020 21:06:10 -0400 IronPort-SDR: ay7TFHOeaJW50VAXg7l3jaenbZgbJsPVBDEB4Y+bVy36KnY9b5Op1l+e93oEBA9LSNX4H0Z+/+ gFdRlu6zEybg== X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga003.jf.intel.com ([10.7.209.27]) by fmsmga101.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 24 Mar 2020 18:06:09 -0700 IronPort-SDR: z5R6lpjG8+2Oc1MM89RRMHOBYnTW4DVLrjfbD/wS/e2JrgHpwwTPP0nHfUphaKQqI2BmxmGIG/ bf8OkxO1AWWg== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.72,302,1580803200"; d="scan'208";a="246951513" Received: from joy-optiplex-7040.sh.intel.com (HELO joy-OptiPlex-7040) ([10.239.13.16]) by orsmga003.jf.intel.com with ESMTP; 24 Mar 2020 18:06:03 -0700 Date: Tue, 24 Mar 2020 20:56:32 -0400 From: Yan Zhao To: Alex Williamson Cc: "Dr. David Alan Gilbert" , "cjia@nvidia.com" , "kvm@vger.kernel.org" , "aik@ozlabs.ru" , "Zhengxiao.zx@alibaba-inc.com" , "shuangtai.tst@alibaba-inc.com" , "qemu-devel@nongnu.org" , "kwankhede@nvidia.com" , "eauger@redhat.com" , "Liu, Yi L" , "Yang, Ziye" , "mlevitsk@redhat.com" , "pasic@linux.ibm.com" , "libvir-list@redhat.com" , "felipe@nutanix.com" , "Ken.Xue@amd.com" , "Tian, Kevin" , "zhenyuw@linux.intel.com" , "dinechin@redhat.com" , "intel-gvt-dev@lists.freedesktop.org" , "Liu, Changpeng" , "berrange@redhat.com" , "cohuck@redhat.com" , "linux-kernel@vger.kernel.org" , "Wang, Zhi A" , "jonathan.davies@nutanix.com" , "He, Shaopeng" Subject: Re: [PATCH v4 0/2] introduction of migration_version attribute for VFIO live migration Message-ID: <20200325005631.GA20109@joy-OptiPlex-7040> Reply-To: Yan Zhao References: <20190531004438.24528-1-yan.y.zhao@intel.com> <20190603132932.1b5dc7fe@x1.home> <20190604003422.GA30229@joy-OptiPlex-7040> <20200323152959.1c39e9a7@w520.home> <20200324035316.GE5456@joy-OptiPlex-7040> <20200324092331.GA2645@work-vm> <20200324084954.0dd835e2@w520.home> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200324084954.0dd835e2@w520.home> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Mar 24, 2020 at 10:49:54PM +0800, Alex Williamson wrote: > On Tue, 24 Mar 2020 09:23:31 +0000 > "Dr. David Alan Gilbert" wrote: > > > * Yan Zhao (yan.y.zhao@intel.com) wrote: > > > On Tue, Mar 24, 2020 at 05:29:59AM +0800, Alex Williamson wrote: > > > > On Mon, 3 Jun 2019 20:34:22 -0400 > > > > Yan Zhao wrote: > > > > > > > > > On Tue, Jun 04, 2019 at 03:29:32AM +0800, Alex Williamson wrote: > > > > > > On Thu, 30 May 2019 20:44:38 -0400 > > > > > > Yan Zhao wrote: > > > > > > > > > > > > > This patchset introduces a migration_version attribute under sysfs of VFIO > > > > > > > Mediated devices. > > > > > > > > > > > > > > This migration_version attribute is used to check migration compatibility > > > > > > > between two mdev devices of the same mdev type. > > > > > > > > > > > > > > Patch 1 defines migration_version attribute in > > > > > > > Documentation/vfio-mediated-device.txt > > > > > > > > > > > > > > Patch 2 uses GVT as an example to show how to expose migration_version > > > > > > > attribute and check migration compatibility in vendor driver. > > > > > > > > > > > > Thanks for iterating through this, it looks like we've settled on > > > > > > something reasonable, but now what? This is one piece of the puzzle to > > > > > > supporting mdev migration, but I don't think it makes sense to commit > > > > > > this upstream on its own without also defining the remainder of how we > > > > > > actually do migration, preferably with more than one working > > > > > > implementation and at least prototyped, if not final, QEMU support. I > > > > > > hope that was the intent, and maybe it's now time to look at the next > > > > > > piece of the puzzle. Thanks, > > > > > > > > > > > > Alex > > > > > > > > > > Got it. > > > > > Also thank you and all for discussing and guiding all along:) > > > > > We'll move to the next episode now. > > > > > > > > Hi Yan, > > > > > > > > As we're hopefully moving towards a migration API, would it make sense > > > > to refresh this series at the same time? I think we're still expecting > > > > a vendor driver implementing Kirti's migration API to also implement > > > > this sysfs interface for compatibility verification. Thanks, > > > > > > > Hi Alex > > > Got it! > > > Thanks for reminding of this. And as now we have vfio-pci implementing > > > vendor ops to allow live migration of pass-through devices, is it > > > necessary to implement similar sysfs node for those devices? > > > or do you think just PCI IDs of those devices are enough for libvirt to > > > know device compatibility ? > > > > Wasn't the problem that we'd have to know how to check for things like: > > a) Whether different firmware versions in the device were actually > > compatible > > b) Whether minor hardware differences were compatible - e.g. some > > hardware might let you migrate to the next version of hardware up. > > Yes, minor changes in hardware or firmware that may not be represented > in the device ID or hardware revision. Also the version is as much for > indicating the compatibility of the vendor defined migration protocol > as it is for the hardware itself. I certainly wouldn't be so bold as > to create a protocol that is guaranteed compatible forever. We'll need > to expose the same sysfs attribute in some standard location for > non-mdev devices. I assume vfio-pci would provide the vendor ops some > mechanism to expose these in a standard namespace of sysfs attributes > under the device itself. Perhaps that indicates we need to link the > mdev type version under the mdev device as well to make this > transparent to userspace tools like libvirt. Thanks, > Got it. will do it. Thanks! Yan