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Miller" , Kirti Wankhede , Cornelia Huck , "kvm@vger.kernel.org" , "linux-kernel@vger.kernel.org" , cjia , "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: AQHVTfNxjgfwJJG2ZUiuOAmKCwQvf6bx3uKAgAWJU4CAAcVCEIAABCsAgAAWVtCAABCDgIAAzoewgAAqE4CAAECFQIAAFWyAgAAGbNCAABfqAIAAErcwgAjpulCAAJkHAIAAnVNggAAbk4CAAAOYgIAABpwAgAAAVrCAAAfEAIAADNCggAHJU4CAAAIMEIAABiaAgAAA2ACAACadAIAAFGdwgAE42YCAAABasA== Date: Fri, 23 Aug 2019 08:14:39 +0000 Message-ID: References: <20190820225722.237a57d2@x1.home> <20190820232622.164962d3@x1.home> <20190822092903.GA2276@nanopsycho.orion> <20190822095823.GB2276@nanopsycho.orion> <20190822121936.GC2276@nanopsycho.orion> <20190823081221.GG2276@nanopsycho.orion> In-Reply-To: <20190823081221.GG2276@nanopsycho.orion> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: authentication-results: spf=none (sender IP is ) smtp.mailfrom=parav@mellanox.com; x-originating-ip: [106.51.18.188] x-ms-publictraffictype: Email x-ms-office365-filtering-correlation-id: aaf830ed-4dcf-4472-4ee0-08d727a1f214 x-ms-office365-filtering-ht: Tenant x-microsoft-antispam: BCL:0;PCL:0;RULEID:(2390118)(7020095)(4652040)(8989299)(5600166)(711020)(4605104)(1401327)(4618075)(4534185)(7168020)(4627221)(201703031133081)(201702281549075)(8990200)(2017052603328)(7193020);SRVR:AM0PR05MB5842; x-ms-traffictypediagnostic: AM0PR05MB5842: x-ld-processed: a652971c-7d2e-4d9b-a6a4-d149256f461b,ExtAddr x-ms-exchange-transport-forked: True x-microsoft-antispam-prvs: x-ms-oob-tlc-oobclassifiers: OLM:10000; x-forefront-prvs: 0138CD935C x-forefront-antispam-report: SFV:NSPM;SFS:(10009020)(4636009)(39860400002)(136003)(396003)(376002)(346002)(366004)(13464003)(199004)(189003)(8936002)(2906002)(14444005)(6436002)(25786009)(99286004)(316002)(66066001)(9456002)(53936002)(256004)(54906003)(74316002)(81166006)(6246003)(81156014)(71200400001)(71190400001)(8676002)(305945005)(7736002)(11346002)(6116002)(3846002)(14454004)(6916009)(9686003)(7696005)(33656002)(561944003)(55016002)(6506007)(53546011)(55236004)(102836004)(5660300002)(186003)(229853002)(52536014)(476003)(486006)(26005)(66476007)(66556008)(86362001)(4326008)(446003)(76116006)(478600001)(76176011)(66446008)(64756008)(66946007);DIR:OUT;SFP:1101;SCL:1;SRVR:AM0PR05MB5842;H:AM0PR05MB4866.eurprd05.prod.outlook.com;FPR:;SPF:None;LANG:en;PTR:InfoNoRecords;A:1;MX:1; received-spf: None (protection.outlook.com: mellanox.com does not designate permitted sender hosts) x-ms-exchange-senderadcheck: 1 x-microsoft-antispam-message-info: 68InJ8pd9oc6SZ03V66KWABna3dVdZzSXkT5ZqgElvidCtUgm7nx6zdrlAqmbXHb58x8vAsyPqKJGy3JsCNfK9OLPQ22CGm8HEPOblN2AruLAsFGzJ51NGBe24P1tkGnc1AFazxz8ydBzZ3FNcq/7OMf5Qx9IQkOdngCXAF0rwRxys6hteOZNk68cq0mLYK/8sq6rUjXAM8IAYERyAVpP5Moy87tuAgt0G9QIr6/OP1VFsg4/4w89n7gzcHCxtS0gcctvFi+LMeq0wwsomwM0eBKfEQt1TU3/JO7RZH0yIQawLfrtwjnyT4IGZuM4FgMcl2qYqOM586D9y+bl4I6ZWLKZ8GitHMPQ/8/JyE78u/sJX3Kr3epFu4Xgcidx3YugvPZS7pcqneQB7ZhRCIkbWB41VGiREy12qcVGGcjmjA= Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-OriginatorOrg: Mellanox.com X-MS-Exchange-CrossTenant-Network-Message-Id: aaf830ed-4dcf-4472-4ee0-08d727a1f214 X-MS-Exchange-CrossTenant-originalarrivaltime: 23 Aug 2019 08:14:39.7381 (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: tB3Pz+Y2AnTFycE7visR6qs3xijOAG0N8s7Rc+4NtfC9lStMINTSS1tZnMUcvLxVnIe7j02WPYUUoxG47eiR9Q== X-MS-Exchange-Transport-CrossTenantHeadersStamped: AM0PR05MB5842 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Alex, > -----Original Message----- > From: Jiri Pirko > Sent: Friday, August 23, 2019 1:42 PM > To: Parav Pandit > Cc: Alex Williamson ; Jiri Pirko > ; David S . Miller ; Kirti > Wankhede ; Cornelia Huck ; > kvm@vger.kernel.org; linux-kernel@vger.kernel.org; cjia = ; > netdev@vger.kernel.org > Subject: Re: [PATCH v2 0/2] Simplify mtty driver and mdev core >=20 > Thu, Aug 22, 2019 at 03:33:30PM CEST, parav@mellanox.com wrote: > > > > > >> -----Original Message----- > >> From: Jiri Pirko > >> Sent: Thursday, August 22, 2019 5:50 PM > >> To: Parav Pandit > >> Cc: Alex Williamson ; Jiri Pirko > >> ; David S . Miller ; Kirti > >> Wankhede ; Cornelia Huck > ; > >> kvm@vger.kernel.org; linux-kernel@vger.kernel.org; cjia > >> ; netdev@vger.kernel.org > >> Subject: Re: [PATCH v2 0/2] Simplify mtty driver and mdev core > >> > >> Thu, Aug 22, 2019 at 12:04:02PM CEST, parav@mellanox.com wrote: > >> > > >> > > >> >> -----Original Message----- > >> >> From: Jiri Pirko > >> >> Sent: Thursday, August 22, 2019 3:28 PM > >> >> To: Parav Pandit > >> >> Cc: Alex Williamson ; Jiri Pirko > >> >> ; David S . Miller ; Kirti > >> >> Wankhede ; Cornelia Huck > >> ; > >> >> kvm@vger.kernel.org; linux-kernel@vger.kernel.org; cjia > >> >> ; 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 > >> >> >> Sent: Thursday, August 22, 2019 2:59 PM > >> >> >> To: Parav Pandit > >> >> >> Cc: Alex Williamson ; Jiri Pirko > >> >> >> ; David S . Miller ; > >> >> >> Kirti Wankhede ; Cornelia Huck > >> >> ; > >> >> >> kvm@vger.kernel.org; linux-kernel@vger.kernel.org; cjia > >> >> >> ; 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 > >> >> >> >> Sent: Wednesday, August 21, 2019 10:56 AM > >> >> >> >> To: Parav Pandit > >> >> >> >> Cc: Jiri Pirko ; David S . Miller > >> >> >> >> ; Kirti Wankhede > >> >> >> >> ; Cornelia Huck ; > >> >> >> >> kvm@vger.kernel.org; linux-kernel@vger.kernel.org; cjia > >> >> >> >> ; 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 suit= able. > >> >> >> >> > > > > > >> >> >> >> > > > > 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_n= ame. > >> >> >> >This alias from the mdev device's sysfs will be used by the > >> >> >> >udev/systemd to > >> >> >> generate predicable netdev's name. > >> >> >> >Example: enm > >> >> >> > >> >> >> 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 ha= ve. > >> > >12 characters from Alex's suggestion similar to git? >=20 > Ok. >=20 Can you please confirm this scheme looks good now? I like to get patches st= arted. > > > >> > > >> > > >> >> 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, 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)= ...