From: Jiri Pirko <jiri@resnulli.us>
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" <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
Date: Thu, 22 Aug 2019 14:19:36 +0200 [thread overview]
Message-ID: <20190822121936.GC2276@nanopsycho.orion> (raw)
In-Reply-To: <AM0PR05MB4866144FD76C302D04DA04B9D1A50@AM0PR05MB4866.eurprd05.prod.outlook.com>
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 start 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 suitable.
>> >> >> > > > >
>> >> >> > > > > 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 if 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?
Sounds fine to me. Now the question is how many chars do we want to
have.
>
>
>> 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=Etherenet, m=mdev.
>> >
>> >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)...
next prev parent reply other threads:[~2019-08-22 12:19 UTC|newest]
Thread overview: 74+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-02 6:59 [PATCH 0/2] Simplify mtty driver and mdev core Parav Pandit
2019-08-02 6:59 ` [PATCH 1/2] vfio-mdev/mtty: Simplify interrupt generation Parav Pandit
2019-08-06 8:15 ` Cornelia Huck
2019-08-02 6:59 ` [PATCH 2/2] vfio/mdev: Removed unused and redundant API for mdev name Parav Pandit
2019-08-06 8:29 ` Cornelia Huck
2019-08-06 13:12 ` Parav Pandit
2019-08-06 14:18 ` [PATCH v1 0/2] Simplify mtty driver and mdev core Parav Pandit
2019-08-06 14:18 ` [PATCH v1 1/2] vfio-mdev/mtty: Simplify interrupt generation Parav Pandit
2019-08-06 14:18 ` [PATCH v1 2/2] vfio/mdev: Removed unused and redundant API for mdev UUID Parav Pandit
2019-08-07 9:28 ` Cornelia Huck
2019-08-07 16:33 ` Parav Pandit
2019-08-08 8:29 ` Cornelia Huck
2019-08-08 14:01 ` Parav Pandit
2019-08-08 14:12 ` [PATCH v2 0/2] Simplify mtty driver and mdev core Parav Pandit
2019-08-08 14:12 ` [PATCH v2 1/2] vfio-mdev/mtty: Simplify interrupt generation Parav Pandit
2019-08-13 16:39 ` Christoph Hellwig
2019-08-23 20:48 ` Alex Williamson
2019-08-08 14:12 ` [PATCH v2 2/2] vfio/mdev: Removed unused and redundant API for mdev UUID Parav Pandit
2019-08-13 16:39 ` Christoph Hellwig
2019-08-16 15:22 ` Cornelia Huck
2019-08-08 23:02 ` [PATCH v2 0/2] Simplify mtty driver and mdev core Alex Williamson
2019-08-09 8:07 ` Cornelia Huck
2019-08-12 11:35 ` Kirti Wankhede
2019-08-13 14:40 ` Parav Pandit
2019-08-13 14:52 ` Alex Williamson
2019-08-13 16:28 ` Parav Pandit
2019-08-13 16:34 ` Cornelia Huck
2019-08-13 17:11 ` Alex Williamson
2019-08-14 5:54 ` Parav Pandit
2019-08-14 8:01 ` Cornelia Huck
2019-08-14 12:27 ` Parav Pandit
2019-08-14 13:09 ` Cornelia Huck
2019-08-14 13:45 ` Parav Pandit
2019-08-14 14:57 ` Alex Williamson
2019-08-14 16:21 ` Parav Pandit
2019-08-20 8:58 ` Parav Pandit
2019-08-20 9:58 ` Christophe de Dinechin
2019-08-20 11:25 ` Parav Pandit
2019-08-20 16:31 ` Cornelia Huck
2019-08-21 2:42 ` Parav Pandit
2019-08-20 17:19 ` Alex Williamson
2019-08-20 17:55 ` Cornelia Huck
2019-08-21 3:57 ` Parav Pandit
2019-08-21 3:42 ` Parav Pandit
2019-08-21 4:20 ` Alex Williamson
2019-08-21 4:40 ` Parav Pandit
2019-08-21 4:57 ` Alex Williamson
2019-08-21 5:01 ` Parav Pandit
2019-08-21 5:26 ` Alex Williamson
2019-08-21 6:23 ` Parav Pandit
2019-08-22 9:29 ` Jiri Pirko
2019-08-22 9:42 ` Parav Pandit
2019-08-22 9:58 ` Jiri Pirko
2019-08-22 10:04 ` Parav Pandit
2019-08-22 12:19 ` Jiri Pirko [this message]
2019-08-22 13:33 ` Parav Pandit
2019-08-23 8:12 ` Jiri Pirko
2019-08-23 8:14 ` Parav Pandit
2019-08-23 14:28 ` Alex Williamson
2019-08-23 14:53 ` Parav Pandit
2019-08-23 15:04 ` Jiri Pirko
2019-08-23 15:52 ` Alex Williamson
2019-08-23 16:14 ` Parav Pandit
2019-08-23 17:16 ` Alex Williamson
2019-08-23 18:00 ` Parav Pandit
2019-08-23 19:43 ` Alex Williamson
2019-08-24 3:56 ` Parav Pandit
2019-08-24 4:45 ` Parav Pandit
2019-08-24 4:59 ` Alex Williamson
2019-08-24 5:22 ` Parav Pandit
2019-08-13 16:37 ` Christoph Hellwig
2019-08-13 17:40 ` Greg Kroah-Hartman
2019-08-14 5:30 ` Parav Pandit
2019-08-13 14:48 ` Parav Pandit
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