Re: [PATCH v1 2/2] vfio/mdev: Removed unused and redundant API for mdev UUID

From: Cornelia Huck <cohuck@redhat.com>
To: Parav Pandit <parav@mellanox.com>
Cc: "kvm@vger.kernel.org" <kvm@vger.kernel.org>,
	"wankhede@nvidia.com" <wankhede@nvidia.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"alex.williamson@redhat.com" <alex.williamson@redhat.com>,
	"cjia@nvidia.com" <cjia@nvidia.com>
Subject: Re: [PATCH v1 2/2] vfio/mdev: Removed unused and redundant API for mdev UUID
Date: Thu, 8 Aug 2019 10:29:31 +0200	[thread overview]
Message-ID: <20190808102931.40c6b4ae.cohuck@redhat.com> (raw)
In-Reply-To: <AM0PR05MB48664379F91C8FA3D0035B41D1D40@AM0PR05MB4866.eurprd05.prod.outlook.com>

On Wed, 7 Aug 2019 16:33:11 +0000
Parav Pandit <parav@mellanox.com> wrote:

> > -----Original Message-----
> > From: Cornelia Huck <cohuck@redhat.com>
> > Sent: Wednesday, August 7, 2019 2:58 PM
> > To: Parav Pandit <parav@mellanox.com>
> > Cc: kvm@vger.kernel.org; wankhede@nvidia.com; linux-
> > kernel@vger.kernel.org; alex.williamson@redhat.com; cjia@nvidia.com
> > Subject: Re: [PATCH v1 2/2] vfio/mdev: Removed unused and redundant API for
> > mdev UUID
> > 
> > On Tue,  6 Aug 2019 09:18:26 -0500
> > Parav Pandit <parav@mellanox.com> wrote:
> >   
> > > There is no single production driver who is interested in mdev device
> > > uuid. Currently UUID is mainly used to derive a device name.
> > > Additionally mdev device name is already available using core kernel
> > > API dev_name().  
> > 
> > Well, the mdev code actually uses the uuid to check for duplicates before
> > registration with the driver core would fail... I'd just drop the two sentences  
> Yes, it does the check. But its mainly used to derive a device name.
> And to ensure that there are no two devices with duplicate name, it compares with the uuid.
> 
> Even this 16 bytes storage is redundant.
> Subsequently, I will submit a patch to get rid of storing this 16 bytes of UUID too.
> Because for duplicate name check, device name itself is pretty good enough.
> 
> Since I ran out of time and rc-4 is going on, I differed the 3rd simplification patch.

I'm not sure why we'd want to ditch the uuid; it's not like it is
taking up huge amounts of space... and I see the device name being
derived from the unique identifier that is the uuid, and not as the
unique identifier itself.

> 
> Commit message actually came from the thoughts of 3rd patch, but I see that without it, its not so intuitive.
> 
> > talking about the device name, IMHO they don't really add useful information;
> > but I'll leave that decision to the maintainers.
> >   
> > >
> > > Hence removed unused exported symbol.
> > >
> > > Signed-off-by: Parav Pandit <parav@mellanox.com>
> > > ---
> > > Changelog:
> > > v0->v1:
> > >  - Updated commit log to address comments from Cornelia
> > > ---
> > >  drivers/vfio/mdev/mdev_core.c | 6 ------
> > >  include/linux/mdev.h          | 1 -
> > >  2 files changed, 7 deletions(-)  
> > 
> > Reviewed-by: Cornelia Huck <cohuck@redhat.com>  
> Thanks for the review.