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

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Message-ID: <AM0PR05MB4866148E1652A20E43260C35D1A00@AM0PR05MB4866.eurprd05.prod.outlook.com>
Date:   Tue, 27 Aug 2019 16:16:27 +0000
From:   Parav Pandit <parav@...lanox.com>
To:     Alex Williamson <alex.williamson@...hat.com>
CC:     Mark Bloch <markb@...lanox.com>, Jiri Pirko <jiri@...lanox.com>,
        "kwankhede@...dia.com" <kwankhede@...dia.com>,
        "cohuck@...hat.com" <cohuck@...hat.com>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: RE: [PATCH 2/4] mdev: Make mdev alias unique among all mdevs



> -----Original Message-----
> From: Alex Williamson <alex.williamson@...hat.com>
> Sent: Tuesday, August 27, 2019 8:54 PM
> To: Parav Pandit <parav@...lanox.com>
> Cc: Mark Bloch <markb@...lanox.com>; Jiri Pirko <jiri@...lanox.com>;
> kwankhede@...dia.com; cohuck@...hat.com; davem@...emloft.net;
> kvm@...r.kernel.org; linux-kernel@...r.kernel.org; netdev@...r.kernel.org
> Subject: Re: [PATCH 2/4] mdev: Make mdev alias unique among all mdevs
> 
> On Tue, 27 Aug 2019 04:28:37 +0000
> Parav Pandit <parav@...lanox.com> wrote:
> 
> > Hi Mark,
> >
> > > -----Original Message-----
> > > From: Mark Bloch <markb@...lanox.com>
> > > Sent: Tuesday, August 27, 2019 4:32 AM
> > > To: Parav Pandit <parav@...lanox.com>; alex.williamson@...hat.com;
> > > Jiri Pirko <jiri@...lanox.com>; kwankhede@...dia.com;
> > > cohuck@...hat.com; davem@...emloft.net
> > > Cc: kvm@...r.kernel.org; linux-kernel@...r.kernel.org;
> > > netdev@...r.kernel.org
> > > Subject: Re: [PATCH 2/4] mdev: Make mdev alias unique among all
> > > mdevs
> > >
> > >
> > >
> > > On 8/26/19 1:41 PM, Parav Pandit 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@...lanox.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) {
> > >
> > > alias can be NULL here no?
> > >
> > If alias is NULL, tmp->alias would also be null because for given parent either
> we have alias or we don’t.
> > So its not possible to have tmp->alias as null and alias as non null.
> > But it may be good/defensive to add check for both.
> 
> mdev_list is a global list of all mdev devices, how can we make any
> assumptions that an element has the same parent?  Thanks,
> 
Oh yes, right. If tmp->alias is not_null but alias can be NULL.
I will fix the check.

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