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Tue, 24 Mar 2020 09:23:37 +0000 (UTC) Date: Tue, 24 Mar 2020 09:23:31 +0000 From: "Dr. David Alan Gilbert" To: Yan Zhao Subject: Re: [PATCH v4 0/2] introduction of migration_version attribute for VFIO live migration Message-ID: <20200324092331.GA2645@work-vm> 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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200324035316.GE5456@joy-OptiPlex-7040> User-Agent: Mutt/1.13.3 (2020-01-12) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 63.128.21.74 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: "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" , Alex Williamson , "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" Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" * 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. Dave > Thanks > Yan > > -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK