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From:   Parav Pandit <parav@mellanox.com>
To:     Cornelia Huck <cohuck@redhat.com>
CC:     "alex.williamson@redhat.com" <alex.williamson@redhat.com>,
        Jiri Pirko <jiri@mellanox.com>,
        "kwankhede@nvidia.com" <kwankhede@nvidia.com>,
        "davem@davemloft.net" <davem@davemloft.net>,
        "kvm@vger.kernel.org" <kvm@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "netdev@vger.kernel.org" <netdev@vger.kernel.org>
Subject: RE: [PATCH 2/4] mdev: Make mdev alias unique among all mdevs
Thread-Topic: [PATCH 2/4] mdev: Make mdev alias unique among all mdevs
Thread-Index: AQHVXE627FcLaFBgXUa8jSc95m92WKcOy/4AgAAKv2A=
Date:   Tue, 27 Aug 2019 11:08:59 +0000
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References: <20190826204119.54386-1-parav@mellanox.com>
        <20190826204119.54386-3-parav@mellanox.com>
 <20190827122928.752e763b.cohuck@redhat.com>
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> -----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
>=20
> On Mon, 26 Aug 2019 15:41:17 -0500
> Parav Pandit <parav@mellanox.com> wrote:
>=20
> > 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, struc=
t
> device *dev,
> >  			ret =3D -EEXIST;
> >  			goto mdev_fail;
> >  		}
> > +		if (tmp->alias && strcmp(tmp->alias, alias) =3D=3D 0) {
>=20
> Any way we can relay to the caller that the uuid was fine, but that we ha=
d a
> hash collision? Duplicate uuids are much more obvious than a collision he=
re.
>=20
How do you want to relay this rare event?
Netlink interface has way to return the error message back, but sysfs is li=
mited due to its error code based interface.

> > +			mutex_unlock(&mdev_list_lock);
> > +			ret =3D -EEXIST;
> > +			goto mdev_fail;
> > +		}
> >  	}
> >
> >  	mdev =3D kzalloc(sizeof(*mdev), GFP_KERNEL);