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Re: device compatibility interface for live migration with assigned devices



On Wed, 05 Aug 2020 12:35:01 +0100
Sean Mooney <smooney redhat com> wrote:

> On Wed, 2020-08-05 at 12:53 +0200, Jiri Pirko wrote:
> > Wed, Aug 05, 2020 at 11:33:38AM CEST, yan y zhao intel com wrote:  

(...)

> > >    software_version: device driver's version.
> > >               in <major>.<minor>[.bugfix] scheme, where there is no
> > > 	       compatibility across major versions, minor versions have
> > > 	       forward compatibility (ex. 1-> 2 is ok, 2 -> 1 is not) and
> > > 	       bugfix version number indicates some degree of internal
> > > 	       improvement that is not visible to the user in terms of
> > > 	       features or compatibility,
> > > 
> > > vendor specific attributes: each vendor may define different attributes
> > >   device id : device id of a physical devices or mdev's parent pci device.
> > >               it could be equal to pci id for pci devices
> > >   aggregator: used together with mdev_type. e.g. aggregator=2 together
> > >               with i915-GVTg_V5_4 means 2*1/4=1/2 of a gen9 Intel
> > > 	       graphics device.
> > >   remote_url: for a local NVMe VF, it may be configured with a remote
> > >               url of a remote storage and all data is stored in the
> > > 	       remote side specified by the remote url.
> > >   ...  
> just a minor not that i find ^ much more simmple to understand then
> the current proposal with self and compatiable.
> if i have well defiend attibute that i can parse and understand that allow
> me to calulate the what is and is not compatible that is likely going to
> more useful as you wont have to keep maintianing a list of other compatible
> devices every time a new sku is released.
> 
> in anycase thank for actully shareing ^ as it make it simpler to reson about what
> you have previously proposed.

So, what would be the most helpful format? A 'software_version' field
that follows the conventions outlined above, and other (possibly
optional) fields that have to match?

(...)

> > Thanks for the explanation, I'm still fuzzy about the details.
> > Anyway, I suggest you to check "devlink dev info" command we have
> > implemented for multiple drivers.  
> 
> is devlink exposed as a filesytem we can read with just open?
> openstack will likely try to leverage libvirt to get this info but when we
> cant its much simpler to read sysfs then it is to take a a depenency on a commandline
> too and have to fork shell to execute it and parse the cli output.
> pyroute2 which we use in some openstack poject has basic python binding for devlink but im not
> sure how complete it is as i think its relitivly new addtion. if we need to take a dependcy
> we will but that would be a drawback fo devlink not that that is a large one just something
> to keep in mind.

A devlinkfs, maybe? At least for reading information (IIUC, "devlink
dev info" is only about information retrieval, right?)


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