Date:   Wed, 13 Mar 2019 07:07:01 +0100
From:   Jiri Pirko <jiri@...nulli.us>
To:     Jakub Kicinski <jakub.kicinski@...ronome.com>
Cc:     davem@...emloft.net, netdev@...r.kernel.org,
        oss-drivers@...ronome.com
Subject: Re: [PATCH net-next v2 4/7] devlink: allow subports on devlink PCI
 ports

Tue, Mar 12, 2019 at 09:56:28PM CET, jakub.kicinski@...ronome.com wrote:
>On Tue, 12 Mar 2019 15:02:39 +0100, Jiri Pirko wrote:
>> Tue, Mar 12, 2019 at 03:10:54AM CET, wrote:
>> >On Mon, 11 Mar 2019 09:52:04 +0100, Jiri Pirko wrote:  
>> >> Fri, Mar 08, 2019 at 08:09:43PM CET, wrote:  
>> >> >If the switchport is in the hypervisor then only the hypervisor can
>> >> >control switching/forwarding, correct?    
>> >> 
>> >> Correct.
>> >>   
>> >> >The primary use case for partitioning within a VM (of a VF) would be
>> >> >containers (and DPDK)?    
>> >> 
>> >> Makes sense.
>> >>   
>> >> >SR-IOV makes things harder.  Splitting a PF is reasonably easy to grasp.
>> >> >I'm trying to get a sense of is how would we control an SR-IOV
>> >> >environment as a whole.    
>> >> 
>> >> You mean orchestration?   
>> >
>> >Right, orchestration.
>> >
>> >To be clear on where I'm going with this - if we want to allow VFs 
>> >to partition themselves then they have to control what is effectively 
>> >a "nested" switch.  A per-VF set of rules which would the get  
>> 
>> Wait. If you allow to make VF subports (I believe that is what you ment
>> by VFs partition themselves), that does not mean they will have a
>> separate nested switch. They would still belong under the same one.
>
>But that existing switch is administered by the hypervisor, how would
>the VF owners install forwarding rules in a switch they don't control?

They won't.


>
>> >"flattened" into the main eswitch rule set.  If I was to choose I'd
>> >really rather have this "flattening" be done on the (Linux) hypervisor
>> >and not in the vendor driver and firmware.  
>> 
>> Agreed. Driver should provide one big switch. User should configure it.
>
>Cool, when you say user - is it the tenant or the provider?

Whoever gets access to the instance.


>
>> >I'd much rather have the VM make a "give me another NIC" orchestration
>> >call via some high level REST API than devlink.  This makes the
>> >configuration strictly high level to low level:
>> >
>> >  VM -> cloud net REST API -> cloud agent -> devlink/Linux -> FW -> HW
>> >
>> >Without round trips via firmware.    
>> 
>> Okay. So the "devlink/Linux -> FW" part is going to happen on baremetal.
>> Makes sense.
>> 
>> >This allows for easy policy enforcement, common code to be maintained
>> >in user space, in high level languages (no 0.5M LoC drivers and 10M LoC
>> >firmware for every driver).  It can also be used with software paths
>> >like VirtIO..  
>> 
>> Agreed.
>> 
>> >Modelling and debugging a nested switch would be a nightmare.  What
>> >follows is that we probably shouldn't deal with partitioning of VFs,
>> >but rather only partition via the PF devlink instance, and reassign 
>> >the partitions to VMs.  
>> 
>> Agreed. That must be misunderstanding, I never suggested nested
>> switches.
>
>Cool, yes, I was making sure we weren't going in that direction :)

Okay.


>
>> >> I originally planned to implement sriov orchestration api in devlink too.  
>> >
>> >Interesting, would you mind elaborating?  
>> 
>> I have to think about it. But something like this:
>> [...]
>
>I see thanks for the examples, they makes things clear!

Okay. I will put together some documentation including this. I have some
patches that implement some of the stuff. Your patchset also does some
of that (considering you adjust a thing or two). Lets make this right. 

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