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

Parav Pandit
2019-08-27T11:09:11Z

> -----Original Message-----
> From: Cornelia Huck <cohuck@redhat.com>
> Sent: Tuesday, August 27, 2019 3:59 PM
> To: Parav Pandit <parav@mellanox.com>
> Cc: alex.williamson@redhat.com; Jiri Pirko <jiri@mellanox.com>;
> kwankhede@nvidia.com; davem@davemloft.net; kvm@vger.kernel.org; linux-
> kernel@vger.kernel.org; netdev@vger.kernel.org
> 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@mellanox.com> 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@mellanox.com>
> > ---
> > 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);