netdev - Re: [PATCH net-next v2 4/7] devlink: allow subports on devlink PCI ports

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Date:   Thu, 14 Mar 2019 15:09:45 -0700
From:   Jakub Kicinski <jakub.kicinski@...ronome.com>
To:     Jiri Pirko <jiri@...nulli.us>
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

On Thu, 14 Mar 2019 08:38:40 +0100, Jiri Pirko wrote:
> Wed, Mar 13, 2019 at 05:55:55PM CET, jakub.kicinski@...ronome.com wrote:
> >On Wed, 13 Mar 2019 17:22:43 +0100, Jiri Pirko wrote:  
> >> Wed, Mar 13, 2019 at 05:17:31PM CET, jakub.kicinski@...ronome.com wrote:  
> >> >On Wed, 13 Mar 2019 07:07:01 +0100, Jiri Pirko wrote:    
> >> >> 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.    
> >> >
> >> >Argh.  So how is forwarding configured if there are no rules?  Are you
> >> >going to assume its switching on MACs?  We're supposed to offload
> >> >software constructs.  If its a software port it needs to be explicitly
> >> >switched.  If it's not explicitly switched - we already have macvlan
> >> >offload.    
> >> 
> >> Wait a second. You configure the switch. And for that, you have the
> >> switchports (representors). What we are talking about are VF (VF
> >> subport) host legs. Am I missing something?  
> >
> >Hm :)  So when VM gets a new port, how is it connected?  Are we
> >assuming all ports of a VM are plugged into one big L2 switch?
> >The use case for those sub ports is a little murky, sorry about
> >the endless confusion :)  
> 
> Np. When user John (on baremetal, or whenever the devlink instance
> with switch port is) creates VF of VF subport by: 
> $ devlink dev port add pci/0000:05:00.0 flavour pci_vf pf 0
> or by:
> $ devlink dev port add pci/0000:05:00.0 flavour pci_vf pf 0 vf 0
> 
> Then instances of flavour pci_vf are going to appear in the same devlink
> instance. Those are the switch ports:
> pci/0000:05:00.0/10002: type eth netdev enp5s0npf0pf0s0
>                         flavour pci_vf pf 0 vf 0
>                         switch_id 00154d130d2f peer pci/0000:05:10.1/0    
> pci/0000:05:00.0/10003: type eth netdev enp5s0npf0pf0s0
>                         flavour pci_vf pf 0 vf 0 subport 1
>                         switch_id 00154d130d2f peer pci/0000:05:10.1/1
> 
> With that, peers are going to appear too, and those are the actual VF/VF
> subport:
> pci/0000:05:10.1/0: type eth netdev ??? flavour pci_vf_host
>                     peer pci/0000:05:00.0/10002
> pci/0000:05:10.1/1: type eth netdev ??? flavour pci_vf_host
>                     peer pci/0000:05:00.0/10003
> 
> Later you can push this VF along with all subports to VM. So in VM, you
> are going to see the VF like this:
> $ devlink dev
> pci/0000:00:08.0
> $ devlink port
> pci/0000:00:08.0/0: type eth netdev ??? flavour pci_vf_host
> pci/0000:00:08.0/1: type eth netdev ??? flavour pci_vf_host
> 
> And back to your question of how are they connected in eswitch.
> That is totally up to the original user John who did the creation.
> He is in charge of the eswitch on baremetal, he would configure
> the forwarding however he likes.

Ack, so I think you're saying VM has to communicate to the cloud
environment to have this provisioned using some service API, not 
a kernel API.  That's what I wanted to confirm.

I don't see any benefit to having the "host ports" under devlink,
as such I think it's a matter of preference.  I'll try to describe 
the two options to Netronome's FAEs and see which one they find more
intuitive.

Makes sense?