Re: device compatibility interface for live migration with assigned devices

On Thu, 20 Aug 2020 08:39:22 +0800 Yan Zhao <yan.y.zhao(a)intel.com&gt; wrote: > On Tue, Aug 18, 2020 at 11:36:52AM +0200, Cornelia Huck wrote: > > On Tue, 18 Aug 2020 10:16:28 +0100 > > Daniel P. Berrangé <berrange(a)redhat.com&gt; wrote: > > > > > On Tue, Aug 18, 2020 at 05:01:51PM +0800, Jason Wang wrote: > > > > On 2020/8/18 下午4:55, Daniel P. Berrangé wrote: > > > > > > > > On Tue, Aug 18, 2020 at 11:24:30AM +0800, Jason Wang wrote: > > > > > > > > On 2020/8/14 下午1:16, Yan Zhao wrote: > > > > > > > > On Thu, Aug 13, 2020 at 12:24:50PM +0800, Jason Wang wrote: > > > > > > > > On 2020/8/10 下午3:46, Yan Zhao wrote: > > > > > > > we actually can also retrieve the same information through sysfs, .e.g > > > > > > > > |- [path to device] > > > > |--- migration > > > > | |--- self > > > > | | |---device_api > > > > | | |---mdev_type > > > > | | |---software_version > > > > | | |---device_id > > > > | | |---aggregator > > > > | |--- compatible > > > > | | |---device_api > > > > | | |---mdev_type > > > > | | |---software_version > > > > | | |---device_id > > > > | | |---aggregator > > > > > > > > > > > > Yes but: > > > > > > > > - You need one file per attribute (one syscall for one attribute) > > > > - Attribute is coupled with kobject > > > > Is that really that bad? You have the device with an embedded kobject > > anyway, and you can just put things into an attribute group? > > > > [Also, I think that self/compatible split in the example makes things > > needlessly complex. Shouldn't semantic versioning and matching already > > cover nearly everything? I would expect very few cases that are more > > complex than that. Maybe the aggregation stuff, but I don't think we > > need that self/compatible split for that, either.] > Hi Cornelia, > > The reason I want to declare compatible list of attributes is that > sometimes it's not a simple 1:1 matching of source attributes and target attributes > as I demonstrated below, > source mdev of (mdev_type i915-GVTg_V5_2 + aggregator 1) is compatible to > target mdev of (mdev_type i915-GVTg_V5_4 + aggregator 2), > (mdev_type i915-GVTg_V5_8 + aggregator 4) > > and aggragator may be just one of such examples that 1:1 matching does not > fit. If you're suggesting that we need a new 'compatible' set for every aggregation, haven't we lost the purpose of aggregation? For example, rather than having N mdev types to represent all the possible aggregation values, we have a single mdev type with N compatible migration entries, one for each possible aggregation value. BTW, how do we have multiple compatible directories? compatible0001, compatible0002? Thanks,