netdev - RE: [PATCH net-next 00/13] Add mlx5 subfunction support

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Date:   Tue, 17 Nov 2020 18:50:57 +0000
From:   Parav Pandit <parav@...dia.com>
To:     Jakub Kicinski <kuba@...nel.org>
CC:     Saeed Mahameed <saeed@...nel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        Jiri Pirko <jiri@...dia.com>, Jason Gunthorpe <jgg@...dia.com>,
        "dledford@...hat.com" <dledford@...hat.com>,
        "Leon Romanovsky" <leonro@...dia.com>,
        "davem@...emloft.net" <davem@...emloft.net>
Subject: RE: [PATCH net-next 00/13] Add mlx5 subfunction support

Hi Jakub,

> From: Jakub Kicinski <kuba@...nel.org>
> Sent: Tuesday, November 17, 2020 10:41 PM
> 
> On Tue, 17 Nov 2020 04:08:57 +0000 Parav Pandit wrote:
> > > On Mon, 16 Nov 2020 16:06:02 -0800 Saeed Mahameed wrote:
> > > > > > Subfunction support is discussed in detail in RFC [1] and [2].
> > > > > > RFC [1] and extension [2] describes requirements, design, and
> > > > > > proposed plumbing using devlink, auxiliary bus and sysfs for
> > > > > > systemd/udev support.
> > > > >
> > > > > So we're going to have two ways of adding subdevs? Via devlink
> > > > > and via the new vdpa netlink thing?
> > Nop.
> > Subfunctions (subdevs) are added only one way, i.e. devlink port as
> > settled in RFC [1].
> >
> > Just to refresh all our memory, we discussed and settled on the flow
> > in [2]; RFC [1] followed this discussion.
> >
> > vdpa tool of [3] can add one or more vdpa device(s) on top of already
> > spawned PF, VF, SF device.
> 
> Nack for the networking part of that. It'd basically be VMDq.
> 
Can you please clarify which networking part do you mean?
Which patches exactly in this patchset?

> > > > Via devlink you add the Sub-function bus device - think of it as
> > > > spawning a new VF - but has no actual characteristics
> > > > (netdev/vpda/rdma) "yet" until user admin decides to load an
> > > > interface on it via aux sysfs.
> > >
> > > By which you mean it doesn't get probed or the device type is not
> > > set (IOW it can still become a block device or netdev depending on
> > > the vdpa request)?
> > > > Basically devlink adds a new eswitch port (the SF port) and
> > > > loading the drivers and the interfaces is done via the auxbus
> > > > subsystem only after the SF is spawned by FW.
> > >
> > > But why?
> > >
> > > Is this for the SmartNIC / bare metal case? The flow for spawning on
> > > the local host gets highly convoluted.
> >
> > The flow of spawning for (a) local host or (b) for external host
> > controller from smartnic is same.
> >
> > $ devlink port add..
> > [..]
> > Followed by
> > $ devlink port function set state...
> >
> > Only change would be to specify the destination where to spawn it.
> > (controller number, pf, sf num etc) Please refer to the detailed
> > examples in individual patch. Patch 12 and 13 mostly covers the
> > complete view.
> 
> Please share full examples of the workflow.
> 
Please find the full example sequence below, taken from this cover letter and from the respective patches 12 and 13.

Change device to switchdev mode:
$ devlink dev eswitch set pci/0000:06:00.0 mode switchdev

Add a devlink port of subfunction flavour:
$ devlink port add pci/0000:06:00.0 flavour pcisf pfnum 0 sfnum 88

Configure mac address of the port function: (existing API).
$ devlink port function set ens2f0npf0sf88 hw_addr 00:00:00:00:88:88

Now activate the function:
$ devlink port function set ens2f0npf0sf88 state active

Now use the auxiliary device and class devices:
$ devlink dev show
pci/0000:06:00.0
auxiliary/mlx5_core.sf.4

$ devlink port show auxiliary/mlx5_core.sf.4/1
auxiliary/mlx5_core.sf.4/1: type eth netdev p0sf88 flavour virtual port 0 splittable false

$ ip link show
127: ens2f0np0: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN mode DEFAULT group default qlen 1000
    link/ether 24:8a:07:b3:d1:12 brd ff:ff:ff:ff:ff:ff
    altname enp6s0f0np0
129: p0sf88: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN mode DEFAULT group default qlen 1000
    link/ether 00:00:00:00:88:88 brd ff:ff:ff:ff:ff:ff

$ rdma dev show
43: rdmap6s0f0: node_type ca fw 16.28.1002 node_guid 248a:0703:00b3:d112 sys_image_guid 248a:0703:00b3:d112
44: mlx5_0: node_type ca fw 16.28.1002 node_guid 0000:00ff:fe00:8888 sys_image_guid 248a:0703:00b3:d112

At this point vdpa tool of [1] can create one or more vdpa net devices on this subfunction device in below sequence.

$ vdpa parentdev list
auxiliary/mlx5_core.sf.4
  supported_classes
    net

$ vdpa dev add parentdev auxiliary/mlx5_core.sf.4 type net name foo0

$ vdpa dev show foo0
foo0: parentdev auxiliary/mlx5_core.sf.4 type network parentdev vdpasim vendor_id 0 max_vqs 2 max_vq_size 256

> I'm asking how the vdpa API fits in with this, and you're showing me the two
> devlink commands we already talked about in the past.
Oh ok, sorry, my bad. I understood your question now about relation of vdpa commands with this.
Please look at the above example sequence that covers the vdpa example also.

[1] https://lore.kernel.org/netdev/20201112064005.349268-1-parav@nvidia.com/