Re: [PATCH v3 0/2] VFIO mdev aggregated resources handling

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

On Wed, Jul 08, 2020 at 09:54:19AM +0800, Zhenyu Wang wrote:
> On 2020.07.07 19:06:34 -0600, Alex Williamson wrote:
> > On Tue, 7 Jul 2020 23:28:39 +0000
> > "Tian, Kevin" <kevin.tian@intel.com> wrote:
> > 
> > > Hi, Alex, 
> > > 
> > > Gentle ping... Please let us know whether this version looks good.
> > 
> > I figured this is entangled with the versioning scheme.  There are
> > unanswered questions about how something that assumes a device of a
> > given type is software compatible to another device of the same type
> > handles aggregation and how the type class would indicate compatibility
> > with an aggregated instance.  Thanks,
> > 
> 
> +Yan
> 
> Alex, If no concern on aggregated resources info for instance that would
> be vendor's behavior to determine what type of resources would be aggregated,
> then I'll check with Yan to see how to fulfill this during migration.
> 
> Thanks
>

hi zhenyu and Alex
currently in this series, it looks that aggregated instances are created
in this way:
    echo "<uuid>,aggregate=10" > create

Is that possible that we change it like that:
1. provide a separate attribute named "aggregator" under mdev type.
  |- [parent physical device]
  |--- Vendor-specific-attributes [optional]
  |--- [mdev_supported_types]
  |     |--- [<type-id>]
  |     |   |--- create
+ |     |   |--- aggregator
  |     |   |--- name
  |     |   |--- available_instances
  |     |   |--- device_api
  |     |   |--- description
  |     |   |--- [devices]

normally, the aggregator is read as 0.


2. when we want to create an aggregated instance, we first echo the count
into the aggregator attribute. e.g.
   echo 10 > aggregator
It will switch the mdev type to 10 x original_type. And then,
available_instances and description would be updated accordingly.

3. do the real mdev creation.
   echo <uuid> > create


In this way, before any instance is created, we can use the
migration_version attribute to test if two aggregation mdevs are
migration compatible.

Thanks
Yan