netdev - RE: [PATCH net-next 00/19] Mellanox, mlx5 sub function support

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Date:   Mon, 11 Nov 2019 14:58:18 +0000
From:   Parav Pandit <parav@...lanox.com>
To:     Jiri Pirko <jiri@...nulli.us>
CC:     Jason Gunthorpe <jgg@...pe.ca>,
        Alex Williamson <alex.williamson@...hat.com>,
        Jakub Kicinski <jakub.kicinski@...ronome.com>,
        David M <david.m.ertman@...el.com>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Saeed Mahameed <saeedm@...lanox.com>,
        "kwankhede@...dia.com" <kwankhede@...dia.com>,
        "leon@...nel.org" <leon@...nel.org>,
        "cohuck@...hat.com" <cohuck@...hat.com>,
        Jiri Pirko <jiri@...lanox.com>,
        "linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>,
        Or Gerlitz <gerlitz.or@...il.com>,
        "Jason Wang (jasowang@...hat.com)" <jasowang@...hat.com>
Subject: RE: [PATCH net-next 00/19] Mellanox, mlx5 sub function support



> -----Original Message-----
> From: Jiri Pirko <jiri@...nulli.us>
> Sent: Monday, November 11, 2019 8:18 AM
> Sun, Nov 10, 2019 at 08:48:31PM CET, parav@...lanox.com wrote:
> >
> >> From: Jason Gunthorpe <jgg@...pe.ca>
> >> Sent: Friday, November 8, 2019 6:57 PM
> >> > We should be creating 3 different buses, instead of mdev bus being
> >> > de-
> >> multiplexer of that?
> >> >
> >> > Hence, depending the device flavour specified, create such device
> >> > on right
> >> bus?
> >> >
> >> > For example,
> >> > $ devlink create subdev pci/0000:05:00.0 flavour virtio name foo
> >> > subdev_id 1 $ devlink create subdev pci/0000:05:00.0 flavour mdev
> >> > <uuid> subdev_id 2 $ devlink create subdev pci/0000:05:00.0 flavour
> >> > mlx5 id 1 subdev_id 3
> >>
> >> I like the idea of specifying what kind of interface you want at sub
> >> device creation time. It fits the driver model pretty well and
> >> doesn't require abusing the vfio mdev for binding to a netdev driver.
> >>
> >> > $ devlink subdev pci/0000:05:00.0/<subdev_id> config <params> $
> >> > echo <respective_device_id> <sysfs_path>/bind
> >>
> >> Is explicit binding really needed?
> >No.
> >
> >> If you specify a vfio flavour why shouldn't the vfio driver autoload
> >> and bind to it right away? That is kind of the point of the driver
> >> model...
> >>
> >It some configuration is needed that cannot be passed at device creation
> time, explicit bind later can be used.
> >
> >> (kind of related, but I don't get while all that GUID and lifecycle
> >> stuff in mdev should apply for something like a SF)
> >>
> >GUID is just the name of the device.
> >But lets park this aside for a moment.
> >
> >> > Implement power management callbacks also on all above 3 buses?
> >> > Abstract out mlx5_bus into more generic virtual bus (vdev bus?) so
> >> > that multiple vendors can reuse?
> >>
> >> In this specific case, why does the SF in mlx5 mode even need a bus?
> >> Is it only because of devlink? That would be unfortunate
> >>
> >Devlink is one part due to identifying using bus/dev.
> >How do we refer to its devlink instance of SF without bus/device?
> 
> Question is, why to have devlink instance for SF itself. Same as VF, you don't
mlx5_core has devlink instance for PF and VF for long time now.
Health report, txq/rxq dumps etc all anchored to this devlink instance even for VF. (similar to PF).
And so, SF same framework should work for SF.

> need devlink instance. You only need devlink_port (or
> devlink_subdev) instance on the PF devlink parent for it.
> 
Devlink_port or devlink_subdev are still on eswitch or mgmt side.
They are not present on the side where devlink instance exist on side where txq/rxq/eq etc exist.