RE: [PATCH 2/4] mdev: Make mdev alias unique among all mdevs

[Parav Pandit]

> -----Original Message-----
> From: Cornelia Huck <cohuck@xxxxxxxxxx>
> Sent: Tuesday, August 27, 2019 3:59 PM
> To: Parav Pandit <parav@xxxxxxxxxxxx>
> Cc: alex.williamson@xxxxxxxxxx; Jiri Pirko <jiri@xxxxxxxxxxxx>;
> kwankhede@xxxxxxxxxx; davem@xxxxxxxxxxxxx; kvm@xxxxxxxxxxxxxxx; linux-
> kernel@xxxxxxxxxxxxxxx; netdev@xxxxxxxxxxxxxxx
> Subject: Re: [PATCH 2/4] mdev: Make mdev alias unique among all mdevs
> 
> On Mon, 26 Aug 2019 15:41:17 -0500
> Parav Pandit <parav@xxxxxxxxxxxx> wrote:
> 
> > Mdev alias should be unique among all the mdevs, so that when such
> > alias is used by the mdev users to derive other objects, there is no
> > collision in a given system.
> >
> > Signed-off-by: Parav Pandit <parav@xxxxxxxxxxxx>
> > ---
> >  drivers/vfio/mdev/mdev_core.c | 5 +++++
> >  1 file changed, 5 insertions(+)
> >
> > diff --git a/drivers/vfio/mdev/mdev_core.c
> > b/drivers/vfio/mdev/mdev_core.c index e825ff38b037..6eb37f0c6369
> > 100644
> > --- a/drivers/vfio/mdev/mdev_core.c
> > +++ b/drivers/vfio/mdev/mdev_core.c
> > @@ -375,6 +375,11 @@ int mdev_device_create(struct kobject *kobj, struct
> device *dev,
> >  			ret = -EEXIST;
> >  			goto mdev_fail;
> >  		}
> > +		if (tmp->alias && strcmp(tmp->alias, alias) == 0) {
> 
> Any way we can relay to the caller that the uuid was fine, but that we had a
> hash collision? Duplicate uuids are much more obvious than a collision here.
> 
How do you want to relay this rare event?
Netlink interface has way to return the error message back, but sysfs is limited due to its error code based interface.

> > +			mutex_unlock(&mdev_list_lock);
> > +			ret = -EEXIST;
> > +			goto mdev_fail;
> > +		}
> >  	}
> >
> >  	mdev = kzalloc(sizeof(*mdev), GFP_KERNEL);