netdev - Re: [PATCH 1/2] vdpa: support set mac address from vdpa tool

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Date: Mon, 17 Jun 2024 13:39:37 +0200
From: Jiri Pirko <jiri@...nulli.us>
To: Parav Pandit <parav@...dia.com>
Cc: Jason Wang <jasowang@...hat.com>, Jakub Kicinski <kuba@...nel.org>,
	Cindy Lu <lulu@...hat.com>, Dragos Tatulea <dtatulea@...dia.com>,
	"mst@...hat.com" <mst@...hat.com>,
	"virtualization@...ts.linux-foundation.org" <virtualization@...ts.linux-foundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"kvm@...r.kernel.org" <kvm@...r.kernel.org>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [PATCH 1/2] vdpa: support set mac address from vdpa tool

Mon, Jun 17, 2024 at 11:44:53AM CEST, parav@...dia.com wrote:
>
>> From: Jiri Pirko <jiri@...nulli.us>
>> Sent: Monday, June 17, 2024 3:09 PM
>> 
>> Mon, Jun 17, 2024 at 04:57:23AM CEST, parav@...dia.com wrote:
>> >
>> >
>> >> From: Jason Wang <jasowang@...hat.com>
>> >> Sent: Monday, June 17, 2024 7:18 AM
>> >>
>> >> On Wed, Jun 12, 2024 at 2:30 PM Jiri Pirko <jiri@...nulli.us> wrote:
>> >> >
>> >> > Wed, Jun 12, 2024 at 03:58:10AM CEST, kuba@...nel.org wrote:
>> >> > >On Tue, 11 Jun 2024 13:32:32 +0800 Cindy Lu wrote:
>> >> > >> Add new UAPI to support the mac address from vdpa tool Function
>> >> > >> vdpa_nl_cmd_dev_config_set_doit() will get the MAC address from
>> >> > >> the vdpa tool and then set it to the device.
>> >> > >>
>> >> > >> The usage is: vdpa dev set name vdpa_name mac **:**:**:**:**:**
>> >> > >
>> >> > >Why don't you use devlink?
>> >> >
>> >> > Fair question. Why does vdpa-specific uapi even exist? To have
>> >> > driver-specific uapi Does not make any sense to me :/
>> >>
>> >> It came with devlink first actually, but switched to a dedicated uAPI.
>> >>
>> >> Parav(cced) may explain more here.
>> >>
>> >Devlink configures function level mac that applies to all protocol devices
>> (vdpa, rdma, netdev) etc.
>> >Additionally, vdpa device level mac can be different (an additional one) to
>> apply to only vdpa traffic.
>> >Hence dedicated uAPI was added.
>> 
>> There is 1:1 relation between vdpa instance and devlink port, isn't it?
>> Then we have:
>>        devlink port function set DEV/PORT_INDEX hw_addr ADDR
>> 
>Above command is privilege command done by the hypervisor on the port function.
>Vpda level setting the mac is similar to a function owner driver setting the mac on the self netdev (even though devlink side has configured some mac for it).
>For example,
>$ ip link set dev wlan1 address 00:11:22:33:44:55

Hmm, under what sceratio exacly this is needed? I mean, the VM that has
VDPA device can actually do that too. That is the actual function owner.


>
>> Which does exactly what you need, configure function hw address (mac).
>> 
>> When you say VDPA traffic, do you suggest there might be VDPA instance and
>> netdev running on the same VF in parallel. If yes, do we have 2 eswitch port
>> representors to be separately used to steer the traffic?
>> If no, how is that supposed to be working?
>A eswitch may allow incoming and outgoing traffic from multiple mac addresses left to the tc rules to decide.
>It does not need two eswitch ports.

Ugh.