From: Parav Pandit <parav@mellanox.com>
To: Alex Williamson <alex.williamson@redhat.com>
Cc: Cornelia Huck <cohuck@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
Date: Tue, 27 Aug 2019 18:54:07 +0000 [thread overview]
Message-ID: <AM0PR05MB48669AA6561A70AECEC8A1CFD1A00@AM0PR05MB4866.eurprd05.prod.outlook.com> (raw)
In-Reply-To: <20190827102435.7bd30ef3@x1.home>
> -----Original Message-----
> From: Alex Williamson <alex.williamson@redhat.com>
> Sent: Tuesday, August 27, 2019 9:55 PM
> To: Parav Pandit <parav@mellanox.com>
> Cc: Cornelia Huck <cohuck@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 Tue, 27 Aug 2019 16:13:27 +0000
> Parav Pandit <parav@mellanox.com> wrote:
>
> > > -----Original Message-----
> > > From: Alex Williamson <alex.williamson@redhat.com>
> > > Sent: Tuesday, August 27, 2019 8:59 PM
> > > To: Cornelia Huck <cohuck@redhat.com>
> > > Cc: Parav Pandit <parav@mellanox.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 Tue, 27 Aug 2019 13:29:46 +0200
> > > Cornelia Huck <cohuck@redhat.com> wrote:
> > >
> > > > On Tue, 27 Aug 2019 11:08:59 +0000 Parav Pandit
> > > > <parav@mellanox.com> wrote:
> > > >
> > > > > > -----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.
> > > >
> > > > I don't know, that's why I asked :)
> > > >
> > > > The problem is that "uuid already used" and "hash collision" are
> > > > indistinguishable. While "use a different uuid" will probably work
> > > > in both cases, "increase alias length" might be a good alternative
> > > > in some cases.
> > > >
> > > > But if there is no good way to relay the problem, we can live with it.
> > >
> > > It's a rare event, maybe just dev_dbg(dev, "Hash collision creating alias
> \"%s\"
> > > for mdev device %pUl\n",...
> > >
> > Ok.
> > dev_dbg_once() to avoid message flood.
>
> I'd suggest a rate-limit rather than a once. The fact that the kernel may have
> experienced a collision at some time in the past does not help someone
> debug why they can't create a device now. The only way we're going to get a
> flood is if a user sufficiently privileged to create mdev devices stumbles onto
> a collision and continues to repeat the same operation. That falls into
> shoot-yourself-in-the-foot behavior imo.
> Thanks,
>
Ok. Will do.
next prev parent reply other threads:[~2019-08-27 18:54 UTC|newest]
Thread overview: 96+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-26 20:41 [PATCH 0/4] Introduce variable length mdev alias Parav Pandit
2019-08-26 20:41 ` [PATCH 1/4] mdev: Introduce sha1 based " Parav Pandit
2019-08-27 1:44 ` Alex Williamson
2019-08-27 1:51 ` Alex Williamson
2019-08-27 4:24 ` Parav Pandit
2019-08-27 10:24 ` Cornelia Huck
2019-08-27 11:12 ` Parav Pandit
2019-08-27 11:24 ` Cornelia Huck
2019-08-27 11:33 ` Parav Pandit
2019-08-27 11:41 ` Cornelia Huck
2019-08-27 11:57 ` Parav Pandit
2019-08-27 13:35 ` Cornelia Huck
2019-08-27 16:50 ` Alex Williamson
2019-08-27 11:16 ` Parav Pandit
2019-08-26 20:41 ` [PATCH 2/4] mdev: Make mdev alias unique among all mdevs Parav Pandit
2019-08-26 23:02 ` Mark Bloch
2019-08-27 4:28 ` Parav Pandit
2019-08-27 15:23 ` Alex Williamson
2019-08-27 16:16 ` Parav Pandit
2019-08-27 10:29 ` Cornelia Huck
2019-08-27 11:08 ` Parav Pandit
2019-08-27 11:29 ` Cornelia Huck
2019-08-27 15:28 ` Alex Williamson
2019-08-27 15:39 ` Cornelia Huck
2019-08-27 16:13 ` Parav Pandit
2019-08-27 16:24 ` Alex Williamson
2019-08-27 18:54 ` Parav Pandit [this message]
2019-08-26 20:41 ` [PATCH 3/4] mdev: Expose mdev alias in sysfs tree Parav Pandit
2019-08-27 1:53 ` Alex Williamson
2019-08-27 3:30 ` Parav Pandit
2019-08-27 10:47 ` Cornelia Huck
2019-08-27 11:07 ` Parav Pandit
2019-08-27 11:34 ` Cornelia Huck
2019-08-27 11:52 ` Parav Pandit
2019-08-27 11:55 ` Cornelia Huck
2019-08-27 12:00 ` Parav Pandit
2019-08-26 20:41 ` [PATCH 4/4] mtty: Optionally support mtty alias Parav Pandit
2019-08-27 13:11 ` [PATCH 0/4] Introduce variable length mdev alias Parav Pandit
2019-08-27 13:31 ` Cornelia Huck
2019-08-27 17:48 ` Alex Williamson
2019-08-27 18:11 ` Parav Pandit
2019-08-27 19:16 ` [PATCH v1 0/5] " Parav Pandit
2019-08-27 19:16 ` [PATCH v1 1/5] mdev: Introduce sha1 based " Parav Pandit
2019-08-28 21:25 ` Alex Williamson
2019-08-28 21:34 ` Alex Williamson
2019-08-29 9:07 ` Parav Pandit
2019-08-29 9:06 ` Parav Pandit
2019-08-27 19:16 ` [PATCH v1 2/5] mdev: Make mdev alias unique among all mdevs Parav Pandit
2019-08-28 21:36 ` Alex Williamson
2019-08-29 9:07 ` Parav Pandit
2019-08-27 19:16 ` [PATCH v1 3/5] mdev: Expose mdev alias in sysfs tree Parav Pandit
2019-08-27 19:16 ` [PATCH v1 4/5] mdev: Update sysfs documentation Parav Pandit
2019-08-27 19:16 ` [PATCH v1 5/5] mtty: Optionally support mtty alias Parav Pandit
2019-08-29 11:18 ` [PATCH v2 0/6] Introduce variable length mdev alias Parav Pandit
2019-08-29 11:18 ` [PATCH v2 1/6] mdev: Introduce sha1 based " Parav Pandit
2019-08-29 12:26 ` Yunsheng Lin
2019-08-30 2:27 ` Parav Pandit
2019-08-30 9:17 ` Cornelia Huck
2019-08-30 12:33 ` Parav Pandit
2019-08-30 12:39 ` Cornelia Huck
2019-08-30 12:58 ` Parav Pandit
2019-08-30 14:02 ` Cornelia Huck
2019-08-30 15:45 ` Parav Pandit
2019-09-02 14:46 ` Cornelia Huck
2019-09-03 3:47 ` Parav Pandit
2019-08-29 11:19 ` [PATCH v2 2/6] mdev: Make mdev alias unique among all mdevs Parav Pandit
2019-08-29 12:31 ` Yunsheng Lin
2019-08-30 12:40 ` Cornelia Huck
2019-08-30 12:59 ` Parav Pandit
2019-08-29 11:19 ` [PATCH v2 3/6] mdev: Expose mdev alias in sysfs tree Parav Pandit
2019-08-29 11:19 ` [PATCH v2 4/6] mdev: Introduce an API mdev_alias Parav Pandit
2019-08-29 11:19 ` [PATCH v2 5/6] mdev: Update sysfs documentation Parav Pandit
2019-08-30 12:49 ` Cornelia Huck
2019-08-30 13:10 ` Parav Pandit
2019-09-02 14:36 ` Cornelia Huck
2019-09-03 3:53 ` Parav Pandit
2019-08-29 11:19 ` [PATCH v2 6/6] mtty: Optionally support mtty alias Parav Pandit
2019-09-02 4:24 ` [PATCH v3 0/5] Introduce variable length mdev alias Parav Pandit
2019-09-02 4:24 ` [PATCH v3 1/5] mdev: Introduce sha1 based " Parav Pandit
2019-09-17 10:03 ` Cornelia Huck
2019-09-02 4:24 ` [PATCH v3 2/5] mdev: Make mdev alias unique among all mdevs Parav Pandit
2019-09-17 10:04 ` Cornelia Huck
2019-09-02 4:24 ` [PATCH v3 3/5] mdev: Expose mdev alias in sysfs tree Parav Pandit
2019-09-17 10:08 ` Cornelia Huck
2019-09-02 4:24 ` [PATCH v3 4/5] mdev: Introduce an API mdev_alias Parav Pandit
2019-09-17 10:10 ` Cornelia Huck
2019-09-02 4:24 ` [PATCH v3 5/5] mtty: Optionally support mtty alias Parav Pandit
2019-09-09 20:42 ` [PATCH v3 0/5] Introduce variable length mdev alias Parav Pandit
2019-09-11 13:56 ` Alex Williamson
2019-09-11 15:30 ` Parav Pandit
2019-09-11 16:29 ` Cornelia Huck
2019-09-11 16:38 ` Parav Pandit
2019-09-13 21:32 ` Alex Williamson
2019-09-13 23:19 ` Parav Pandit
2019-09-17 10:13 ` Cornelia Huck
2019-09-18 17:15 ` Parav Pandit
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