Re: device compatibility interface for live migration with assigned devices

[Yan Zhao <yan.y.zhao@intel.com>]

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@redhat.com> 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.

So, we explicitly list out self/compatible attributes, and management
tools only need to check if self attributes is contained compatible
attributes.

or do you mean only compatible list is enough, and the management tools
need to find out self list by themselves?
But I think provide a self list is easier for management tools.

Thanks
Yan