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

[Alex Williamson]

On Thu, 13 Jun 2019 18:17:53 +0200
Christophe de Dinechin <cdupontd at redhat.com> wrote:

> > On 24 May 2019, at 01:20, Alex Williamson <alex.williamson at redhat.com> wrote:
> > 
> > Hi,
> > 
> > Currently mediated device management, much like SR-IOV VF management,
> > is largely left as an exercise for the user.  This is an attempt to
> > provide something and see where it goes.  I doubt we'll solve
> > everyone's needs on the first pass, but maybe we'll solve enough and
> > provide helpers for the rest.  Without further ado, I'll point to what
> > I have so far:
> > 
> > https://github.com/awilliam/mdevctl  
> 
> While it’s still early, what about :
> 
> 	mdevctl create-mdev <parent-device> <mdev-type> [<mdev-uuid>]
> 
> where if the mdev-uuid is missing, you just run uuidgen within the script?
> 
> I sent a small PR in case you think it makes sense.

It sounds racy.  If the user doesn't provide the UUID then they need to
guess that an mdev device with the same parent and type is theirs.  How
do you resolve two instances of this happening in parallel and both
coming to the same conclusion which is their device.  If a user wants
this sort of headache they can call mdevctl with `uuidgen` but I don't
think we should encourage it further.

BTW, I've moved the project to https://github.com/mdevctl/mdevctl, the
latest commit in the tree above makes that change, I've also updated
the description on my repo to point to the new location.  Thanks,

Alex