[libvirt] mdevctl: A shoestring mediated device management and persistence utility

[Alex Williamson]

On Wed, 26 Jun 2019 08:37:20 -0600
Alex Williamson <alex.williamson at redhat.com> wrote:

> On Wed, 26 Jun 2019 11:58:06 +0200
> Cornelia Huck <cohuck at redhat.com> wrote:
> 
> > On Tue, 25 Jun 2019 16:52:51 -0600
> > Alex Williamson <alex.williamson at redhat.com> wrote:
> >   
> > > Hi,
> > > 
> > > Based on the discussions we've had, I've rewritten the bulk of
> > > mdevctl.  I think it largely does everything we want now, modulo
> > > devices that will need some sort of 1:N values per key for
> > > configuration in the config file versus the 1:1 key:value setup we
> > > currently have (so don't consider the format final just yet).    
> > 
> > We might want to factor out that config format handling while we're
> > trying to finalize it.
> > 
> > cc:ing Matt for his awareness. I'm currently not quite sure how to
> > handle those vfio-ap "write several values to an attribute one at a
> > time" requirements. Maybe 1:N key:value is the way to go; maybe we
> > need/want JSON or something like that.  
> 
> Maybe we should just do JSON for future flexibility.  I assume there
> are lots of helpers that should make it easy even from a bash script.
> I'll look at that next.

Done.  Throw away any old mdev config files, we use JSON now.  The per
mdev config now looks like this:

{
  "mdev_type": "i915-GVTg_V4_8",
  "start": "auto"
}

My expectation, and what I've already pre-enabled support in set_key
and get_key functions, is that we'd use arrays for values, so we might
have:

  "new_key": ["value1", "value2"]

set_key will automatically convert a comma separated list of values
into such an array, so I'm thinking this would be specified by the user
as:

# mdevctl modify -u UUID --key=new_key --value=value1,value2

We should think about whether ordering is important and maybe
incorporate that into key naming conventions or come up with some
syntax for specifying startup blocks.  Thanks,

Alex