Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
From:   Parav Pandit <parav@mellanox.com>
To:     Jiri Pirko <jiri@resnulli.us>
CC:     Alex Williamson <alex.williamson@redhat.com>,
        Jiri Pirko <jiri@mellanox.com>,
        "David S . Miller" <davem@davemloft.net>,
        Kirti Wankhede <kwankhede@nvidia.com>,
        Cornelia Huck <cohuck@redhat.com>,
        "kvm@vger.kernel.org" <kvm@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        cjia <cjia@nvidia.com>,
        "netdev@vger.kernel.org" <netdev@vger.kernel.org>
Subject: RE: [PATCH v2 0/2] Simplify mtty driver and mdev core
Thread-Topic: [PATCH v2 0/2] Simplify mtty driver and mdev core
Thread-Index: AQHVTfNxjgfwJJG2ZUiuOAmKCwQvf6bx3uKAgAWJU4CAAcVCEIAABCsAgAAWVtCAABCDgIAAzoewgAAqE4CAAECFQIAAFWyAgAAGbNCAABfqAIAAErcwgAjpulCAAJkHAIAAnVNggAAbk4CAAAOYgIAABpwAgAAAVrCAAAfEAIAADNCggAHJU4CAAAIMEIAABiaAgAAA2ACAACadAIAAFGdw
Date:   Thu, 22 Aug 2019 13:33:30 +0000
Message-ID: <AM0PR05MB4866F9650CF73FC671972127D1A50@AM0PR05MB4866.eurprd05.prod.outlook.com>
References: <20190820222051.7aeafb69@x1.home>
 <AM0PR05MB48664CDF05C3D02F9441440DD1AA0@AM0PR05MB4866.eurprd05.prod.outlook.com>
 <20190820225722.237a57d2@x1.home>
 <AM0PR05MB4866AE8FC4AA3CC24B08B326D1AA0@AM0PR05MB4866.eurprd05.prod.outlook.com>
 <20190820232622.164962d3@x1.home>
 <AM0PR05MB4866437FAA63C447CACCD7E5D1AA0@AM0PR05MB4866.eurprd05.prod.outlook.com>
 <20190822092903.GA2276@nanopsycho.orion>
 <AM0PR05MB4866A20F831A5D42E6C79EFED1A50@AM0PR05MB4866.eurprd05.prod.outlook.com>
 <20190822095823.GB2276@nanopsycho.orion>
 <AM0PR05MB4866144FD76C302D04DA04B9D1A50@AM0PR05MB4866.eurprd05.prod.outlook.com>
 <20190822121936.GC2276@nanopsycho.orion>
In-Reply-To: <20190822121936.GC2276@nanopsycho.orion>
Accept-Language: en-US
Content-Language: en-US
received-spf: None (protection.outlook.com: mellanox.com does not designate
 permitted sender hosts)
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: quoted-printable
MIME-Version: 1.0
X-MS-Exchange-CrossTenant-Network-Message-Id: 5a67736f-645d-4c6f-5993-08d7270552a6
X-MS-Exchange-CrossTenant-originalarrivaltime: 22 Aug 2019 13:33:30.9808
 (UTC)
X-MS-Exchange-CrossTenant-fromentityheader: Hosted
X-MS-Exchange-CrossTenant-id: a652971c-7d2e-4d9b-a6a4-d149256f461b
X-MS-Exchange-CrossTenant-mailboxtype: HOSTED
X-MS-Exchange-CrossTenant-userprincipalname: a7fhxSAuO40kO0EEmUrdGUH+JqrVlXgwpCKjZT9t2RopNN+XV2FrdYfSCIV4HNdlULwo4DDy0i7CyeEjdG0E+Q==
X-MS-Exchange-Transport-CrossTenantHeadersStamped: AM0PR05MB5875
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org


> -----Original Message-----
> From: Jiri Pirko <jiri@resnulli.us>
> Sent: Thursday, August 22, 2019 5:50 PM
> To: Parav Pandit <parav@mellanox.com>
> Cc: Alex Williamson <alex.williamson@redhat.com>; Jiri Pirko
> <jiri@mellanox.com>; David S . Miller <davem@davemloft.net>; Kirti
> Wankhede <kwankhede@nvidia.com>; Cornelia Huck <cohuck@redhat.com>;
> kvm@vger.kernel.org; linux-kernel@vger.kernel.org; cjia <cjia@nvidia.com>=
;
> netdev@vger.kernel.org
> Subject: Re: [PATCH v2 0/2] Simplify mtty driver and mdev core
>=20
> Thu, Aug 22, 2019 at 12:04:02PM CEST, parav@mellanox.com wrote:
> >
> >
> >> -----Original Message-----
> >> From: Jiri Pirko <jiri@resnulli.us>
> >> Sent: Thursday, August 22, 2019 3:28 PM
> >> To: Parav Pandit <parav@mellanox.com>
> >> Cc: Alex Williamson <alex.williamson@redhat.com>; Jiri Pirko
> >> <jiri@mellanox.com>; David S . Miller <davem@davemloft.net>; Kirti
> >> Wankhede <kwankhede@nvidia.com>; Cornelia Huck
> <cohuck@redhat.com>;
> >> kvm@vger.kernel.org; linux-kernel@vger.kernel.org; cjia
> >> <cjia@nvidia.com>; netdev@vger.kernel.org
> >> Subject: Re: [PATCH v2 0/2] Simplify mtty driver and mdev core
> >>
> >> Thu, Aug 22, 2019 at 11:42:13AM CEST, parav@mellanox.com wrote:
> >> >
> >> >
> >> >> -----Original Message-----
> >> >> From: Jiri Pirko <jiri@resnulli.us>
> >> >> Sent: Thursday, August 22, 2019 2:59 PM
> >> >> To: Parav Pandit <parav@mellanox.com>
> >> >> Cc: Alex Williamson <alex.williamson@redhat.com>; Jiri Pirko
> >> >> <jiri@mellanox.com>; David S . Miller <davem@davemloft.net>; Kirti
> >> >> Wankhede <kwankhede@nvidia.com>; Cornelia Huck
> >> <cohuck@redhat.com>;
> >> >> kvm@vger.kernel.org; linux-kernel@vger.kernel.org; cjia
> >> >> <cjia@nvidia.com>; netdev@vger.kernel.org
> >> >> Subject: Re: [PATCH v2 0/2] Simplify mtty driver and mdev core
> >> >>
> >> >> Wed, Aug 21, 2019 at 08:23:17AM CEST, parav@mellanox.com wrote:
> >> >> >
> >> >> >
> >> >> >> -----Original Message-----
> >> >> >> From: Alex Williamson <alex.williamson@redhat.com>
> >> >> >> Sent: Wednesday, August 21, 2019 10:56 AM
> >> >> >> To: Parav Pandit <parav@mellanox.com>
> >> >> >> Cc: Jiri Pirko <jiri@mellanox.com>; David S . Miller
> >> >> >> <davem@davemloft.net>; Kirti Wankhede <kwankhede@nvidia.com>;
> >> >> >> Cornelia Huck <cohuck@redhat.com>; kvm@vger.kernel.org;
> >> >> >> linux-kernel@vger.kernel.org; cjia <cjia@nvidia.com>;
> >> >> >> netdev@vger.kernel.org
> >> >> >> Subject: Re: [PATCH v2 0/2] Simplify mtty driver and mdev core
> >> >> >>
> >> >> >> > > > > Just an example of the alias, not proposing how it's set=
.
> >> >> >> > > > > In fact, proposing that the user does not set it,
> >> >> >> > > > > mdev-core provides one
> >> >> >> > > automatically.
> >> >> >> > > > >
> >> >> >> > > > > > > Since there seems to be some prefix overhead, as I
> >> >> >> > > > > > > ask about above in how many characters we actually
> >> >> >> > > > > > > have to work with in IFNAMESZ, maybe we start with
> >> >> >> > > > > > > 8 characters (matching your "index" namespace) and
> >> >> >> > > > > > > expand as necessary for
> >> >> disambiguation.
> >> >> >> > > > > > > If we can eliminate overhead in IFNAMESZ, let's star=
t with
> 12.
> >> >> >> > > > > > > Thanks,
> >> >> >> > > > > > >
> >> >> >> > > > > > If user is going to choose the alias, why does it
> >> >> >> > > > > > have to be limited to
> >> >> >> sha1?
> >> >> >> > > > > > Or you just told it as an example?
> >> >> >> > > > > >
> >> >> >> > > > > > It can be an alpha-numeric string.
> >> >> >> > > > >
> >> >> >> > > > > No, I'm proposing a different solution where mdev-core
> >> >> >> > > > > creates an alias based on an abbreviated sha1.  The
> >> >> >> > > > > user does not provide the
> >> >> >> alias.
> >> >> >> > > > >
> >> >> >> > > > > > Instead of mdev imposing number of characters on the
> >> >> >> > > > > > alias, it should be best
> >> >> >> > > > > left to the user.
> >> >> >> > > > > > Because in future if netdev improves on the naming
> >> >> >> > > > > > scheme, mdev will be
> >> >> >> > > > > limiting it, which is not right.
> >> >> >> > > > > > So not restricting alias size seems right to me.
> >> >> >> > > > > > User configuring mdev for networking devices in a
> >> >> >> > > > > > given kernel knows what
> >> >> >> > > > > user is doing.
> >> >> >> > > > > > So user can choose alias name size as it finds suitabl=
e.
> >> >> >> > > > >
> >> >> >> > > > > That's not what I'm proposing, please read again.
> >> >> >> > > > > Thanks,
> >> >> >> > > >
> >> >> >> > > > I understood your point. But mdev doesn't know how user
> >> >> >> > > > is going to use
> >> >> >> > > udev/systemd to name the netdev.
> >> >> >> > > > So even if mdev chose to pick 12 characters, it could
> >> >> >> > > > result in
> >> collision.
> >> >> >> > > > Hence the proposal to provide the alias by the user, as
> >> >> >> > > > user know the best
> >> >> >> > > policy for its use case in the environment its using.
> >> >> >> > > > So 12 character sha1 method will still work by user.
> >> >> >> > >
> >> >> >> > > Haven't you already provided examples where certain drivers
> >> >> >> > > or subsystems have unique netdev prefixes?  If mdev
> >> >> >> > > provides a unique alias within the subsystem, couldn't we
> >> >> >> > > simply define a netdev prefix for the mdev subsystem and
> >> >> >> > > avoid all other collisions?  I'm not in favor of the user
> >> >> >> > > providing both a uuid and an alias/instance.  Thanks,
> >> >> >> > >
> >> >> >> > For a given prefix, say ens2f0, can two UUID->sha1 first 9
> >> >> >> > characters have
> >> >> >> collision?
> >> >> >>
> >> >> >> I think it would be a mistake to waste so many chars on a
> >> >> >> prefix, but
> >> >> >> 9 characters of sha1 likely wouldn't have a collision before we
> >> >> >> have 10s of thousands of devices.  Thanks,
> >> >> >>
> >> >> >> Alex
> >> >> >
> >> >> >Jiri, Dave,
> >> >> >Are you ok with it for devlink/netdev part?
> >> >> >Mdev core will create an alias from a UUID.
> >> >> >
> >> >> >This will be supplied during devlink port attr set such as,
> >> >> >
> >> >> >devlink_port_attrs_mdev_set(struct devlink_port *port, const char
> >> >> >*mdev_alias);
> >> >> >
> >> >> >This alias is used to generate representor netdev's phys_port_name=
.
> >> >> >This alias from the mdev device's sysfs will be used by the
> >> >> >udev/systemd to
> >> >> generate predicable netdev's name.
> >> >> >Example: enm<mdev_alias_first_12_chars>
> >> >>
> >> >> What happens in unlikely case of 2 UUIDs collide?
> >> >>
> >> >Since users sees two devices with same phys_port_name, user should
> >> >destroy
> >> recently created mdev and recreate mdev with different UUID?
> >>
> >> Driver should make sure phys port name wont collide,
> >So when mdev creation is initiated, mdev core calculates the alias and i=
f there
> is any other mdev with same alias exist, it returns -EEXIST error before
> progressing further.
> >This way user will get to know upfront in event of collision before the =
mdev
> device gets created.
> >How about that?
>=20
> Sounds fine to me. Now the question is how many chars do we want to have.
>=20
12 characters from Alex's suggestion similar to git?

> >
> >
> >> in this case that it does
> >> not provide 2 same attrs for 2 different ports.
> >> Hmm, so the order of creation matters. That is not good.
> >>
> >> >>
> >> >> >I took Ethernet mdev as an example.
> >> >> >New prefix 'm' stands for mediated device.
> >> >> >Remaining 12 characters are first 12 chars of the mdev alias.
> >> >>
> >> >> Does this resolve the identification of devlink port representor?
> >> >Not sure if I understood your question correctly, attemping to answer
> below.
> >> >phys_port_name of devlink port is defined by the first 12 characters
> >> >of mdev
> >> alias.
> >> >> I assume you want to use the same 12(or so) chars, don't you?
> >> >Mdev's netdev will also use the same mdev alias from the sysfs to
> >> >rename
> >> netdev name from ethX to enm<mdev_alias>, where en=3DEtherenet,
> m=3Dmdev.
> >> >
> >> >So yes, same 12 characters are use for mdev's netdev and mdev
> >> >devlink port's
> >> phys_port_name.
> >> >
> >> >Is that what are you asking?
> >>
> >> Yes. Then you have 3 chars to handle the rest of the name (pci, pf)...