Re: [PATCH v4 0/2] introduction of migration_version attribute for VFIO live migration

* Yan Zhao (yan.y.zhao(a)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 <yan.y.zhao(a)intel.com&gt; 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 <yan.y.zhao(a)intel.com&gt; 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.