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Date:   Thu, 10 Dec 2020 20:11:42 -0800
From:   "Samudrala, Sridhar" <sridhar.samudrala@...el.com>
To:     saeed@...nel.org, "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Jason Gunthorpe <jgg@...dia.com>
Cc:     Leon Romanovsky <leonro@...dia.com>, netdev@...r.kernel.org,
        linux-rdma@...r.kernel.org, David Ahern <dsahern@...nel.org>,
        Jacob Keller <jacob.e.keller@...el.com>,
        david.m.ertman@...el.com, dan.j.williams@...el.com,
        kiran.patil@...el.com, gregkh@...uxfoundation.org,
        Parav Pandit <parav@...dia.com>
Subject: Re: [PATCH net-next v2 00/14] Add mlx5 subfunction support

On 12/8/2020 11:29 PM, saeed@...nel.org wrote:
> From: Parav Pandit <parav@...dia.com>
>
> Hi Dave, Jakub, Jason,
>
> This series form Parav was the theme of this mlx5 release cycle,
> we've been waiting anxiously for the auxbus infrastructure to make it into
> the kernel, and now as the auxbus is in and all the stars are aligned, I
> can finally submit this V2 of the devlink and mlx5 subfunction support.
>
> Subfunctions came to solve the scaling issue of virtualization
> and switchdev environments, where SRIOV failed to deliver and users ran
> out of VFs very quickly as SRIOV demands huge amount of physical resources
> in both of the servers and the NIC.
>
> Subfunction provide the same functionality as SRIOV but in a very
> lightweight manner, please see the thorough and detailed
> documentation from Parav below, in the commit messages and the
> Networking documentation patches at the end of this series.

What is the mechanism for assigning these subfunctions to VMs?
OR is this only targeted for container usecases at this time?

>
> Sending V2 as a continuation to V1 that was sent Last month [0],
> Parav has provided full change-log in the commit message of each patch.
> [0] https://lore.kernel.org/linux-rdma/20201112192424.2742-1-parav@nvidia.com/
>
> Parav Pandit Says:
> =================
>
> This patchset introduces support for mlx5 subfunction (SF).
>
> A subfunction is a lightweight function that has a parent PCI function on
> which it is deployed. mlx5 subfunction has its own function capabilities
> and its own resources. This means a subfunction has its own dedicated
> queues(txq, rxq, cq, eq). These queues are neither shared nor stealed from
> the parent PCI function.
>
> When subfunction is RDMA capable, it has its own QP1, GID table and rdma
> resources neither shared nor stealed from the parent PCI function.
>
> A subfunction has dedicated window in PCI BAR space that is not shared
> with ther other subfunctions or parent PCI function. This ensures that all
> class devices of the subfunction accesses only assigned PCI BAR space.
>
> A Subfunction supports eswitch representation through which it supports tc
> offloads. User must configure eswitch to send/receive packets from/to
> subfunction port.
>
> Subfunctions share PCI level resources such as PCI MSI-X IRQs with
> their other subfunctions and/or with its parent PCI function.
>
> Patch summary:
> --------------
> Patch 1 to 4 prepares devlink
> patch 5 to 7 mlx5 adds SF device support
> Patch 8 to 11 mlx5 adds SF devlink port support
> Patch 12 and 14 adds documentation
>
> Patch-1 prepares code to handle multiple port function attributes
> Patch-2 introduces devlink pcisf port flavour similar to pcipf and pcivf
> Patch-3 adds port add and delete driver callbacks
> Patch-4 adds port function state get and set callbacks
> Patch-5 mlx5 vhca event notifier support to distribute subfunction
>          state change notification
> Patch-6 adds SF auxiliary device
> Patch-7 adds SF auxiliary driver
> Patch-8 prepares eswitch to handler SF vport
> Patch-9 adds eswitch helpers to add/remove SF vport
> Patch-10 implements devlink port add/del callbacks
> Patch-11 implements devlink port function get/set callbacks
> Patch-12 to 14 adds documentation
> Patch-12 added mlx5 port function documentation
> Patch-13 adds subfunction documentation
> Patch-14 adds mlx5 subfunction documentation
>
> 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. Functionality of this patchset is best explained using real
> examples further below.
>
> overview:
> --------
> A subfunction can be created and deleted by a user using devlink port
> add/delete interface.
>
> A subfunction can be configured using devlink port function attribute
> before its activated.
>
> When a subfunction is activated, it results in an auxiliary device on
> the host PCI device where it is deployed. A driver binds to the
> auxiliary device that further creates supported class devices.
>
> example subfunction usage sequence:
> -----------------------------------
> Change device to switchdev mode:
> $ devlink dev eswitch set pci/0000:06:00.0 mode switchdev
>
> Add a devlink port of subfunction flaovur:
> $ devlink port add pci/0000:06:00.0 flavour pcisf pfnum 0 sfnum 88
Is there any requirement that subfunctions can be created only when 
eswitch mode is set to switchdev?
I think we should not restrict this functionality without switchdev mode .

After this step, i guess an auxiliary device is created on the auxiliary 
bus and a devlink port.
Does "devlink port show" show this port and can we list the auxiliary 
device.
> Configure mac address of the port function:
> $ devlink port function set ens2f0npf0sf88 hw_addr 00:00:00:00:88:88
What is ens2f0npf0sf88? Is this the port representer netdev? I think we 
should allow setting
this by passing the devlink port.

What about other attributes like number of queues, interrupt vectors and 
port
capabilities etc? Can we add other attributes via this interface?
>
> Now activate the function:
> $ devlink port function set ens2f0npf0sf88 state active
Is the subfunction netdev created after this step?
I thought there was a step to bind the auxiliary device to the driver.
How does the probe routine for the auxiliary device get invoked?
>
> Now use the auxiliary device and class devices:
> $ devlink dev show
> pci/0000:06:00.0
> auxiliary/mlx5_core.sf.4
>
> $ 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 16.29.0550 node_guid 248a:0703:00b3:d112 sys_image_guid 248a:0703:00b3:d112
> 44: mlx5_0: node_type ca fw 16.29.0550 node_guid 0000:00ff:fe00:8888 sys_image_guid 248a:0703:00b3:d112
>
> After use inactivate the function:
> $ devlink port function set ens2f0npf0sf88 state inactive
>
> Now delete the subfunction port:
> $ devlink port del ens2f0npf0sf88
>
> [1] https://lore.kernel.org/netdev/20200519092258.GF4655@nanopsycho/
> [2] https://marc.info/?l=linux-netdev&m=158555928517777&w=2
>
> =================
> ---
> Changelog:
> v1->v2:
>   - added documentation for subfunction and its mlx5 implementation
>   - add MLX5_SF config option documentation
>   - rebased
>   - dropped devlink global lock improvement patch as mlx5 doesn't support
>     reload while SFs are allocated
>   - dropped devlink reload lock patch as mlx5 doesn't support reload
>     when SFs are allocated
>   - using updated vhca event from device to add remove auxiliary device
>   - split sf devlink port allocation and sf hardware context allocation
>
> Parav Pandit (13):
>    devlink: Prepare code to fill multiple port function attributes
>    devlink: Introduce PCI SF port flavour and port attribute
>    devlink: Support add and delete devlink port
>    devlink: Support get and set state of port function
>    net/mlx5: Introduce vhca state event notifier
>    net/mlx5: SF, Add auxiliary device support
>    net/mlx5: SF, Add auxiliary device driver
>    net/mlx5: E-switch, Add eswitch helpers for SF vport
>    net/mlx5: SF, Add port add delete functionality
>    net/mlx5: SF, Port function state change support
>    devlink: Add devlink port documentation
>    devlink: Extend devlink port documentation for subfunctions
>    net/mlx5: Add devlink subfunction port documentation
>
> Vu Pham (1):
>    net/mlx5: E-switch, Prepare eswitch to handle SF vport
>
>   Documentation/driver-api/auxiliary_bus.rst    |   2 +
>   .../device_drivers/ethernet/mellanox/mlx5.rst | 209 +++++++
>   .../networking/devlink/devlink-port.rst       | 199 +++++++
>   Documentation/networking/devlink/index.rst    |   1 +
>   .../net/ethernet/mellanox/mlx5/core/Kconfig   |  19 +
>   .../net/ethernet/mellanox/mlx5/core/Makefile  |   9 +
>   drivers/net/ethernet/mellanox/mlx5/core/cmd.c |   8 +
>   .../net/ethernet/mellanox/mlx5/core/devlink.c |  19 +
>   drivers/net/ethernet/mellanox/mlx5/core/eq.c  |   5 +-
>   .../mellanox/mlx5/core/esw/acl/egress_ofld.c  |   2 +-
>   .../mellanox/mlx5/core/esw/devlink_port.c     |  41 ++
>   .../net/ethernet/mellanox/mlx5/core/eswitch.c |  48 +-
>   .../net/ethernet/mellanox/mlx5/core/eswitch.h |  78 +++
>   .../mellanox/mlx5/core/eswitch_offloads.c     |  47 +-
>   .../net/ethernet/mellanox/mlx5/core/events.c  |   7 +
>   .../net/ethernet/mellanox/mlx5/core/main.c    |  60 +-
>   .../ethernet/mellanox/mlx5/core/mlx5_core.h   |  12 +
>   .../net/ethernet/mellanox/mlx5/core/pci_irq.c |  20 +
>   .../net/ethernet/mellanox/mlx5/core/sf/cmd.c  |  48 ++
>   .../ethernet/mellanox/mlx5/core/sf/dev/dev.c  | 271 +++++++++
>   .../ethernet/mellanox/mlx5/core/sf/dev/dev.h  |  55 ++
>   .../mellanox/mlx5/core/sf/dev/driver.c        | 101 ++++
>   .../ethernet/mellanox/mlx5/core/sf/devlink.c  | 552 ++++++++++++++++++
>   .../ethernet/mellanox/mlx5/core/sf/hw_table.c | 235 ++++++++
>   .../mlx5/core/sf/mlx5_ifc_vhca_event.h        |  82 +++
>   .../net/ethernet/mellanox/mlx5/core/sf/priv.h |  21 +
>   .../net/ethernet/mellanox/mlx5/core/sf/sf.h   |  92 +++
>   .../mellanox/mlx5/core/sf/vhca_event.c        | 189 ++++++
>   .../mellanox/mlx5/core/sf/vhca_event.h        |  57 ++
>   .../net/ethernet/mellanox/mlx5/core/vport.c   |   3 +-
>   include/linux/mlx5/driver.h                   |  16 +-
>   include/net/devlink.h                         |  79 +++
>   include/uapi/linux/devlink.h                  |  26 +
>   net/core/devlink.c                            | 266 ++++++++-
>   34 files changed, 2832 insertions(+), 47 deletions(-)
>   create mode 100644 Documentation/networking/devlink/devlink-port.rst
>   create mode 100644 drivers/net/ethernet/mellanox/mlx5/core/sf/cmd.c
>   create mode 100644 drivers/net/ethernet/mellanox/mlx5/core/sf/dev/dev.c
>   create mode 100644 drivers/net/ethernet/mellanox/mlx5/core/sf/dev/dev.h
>   create mode 100644 drivers/net/ethernet/mellanox/mlx5/core/sf/dev/driver.c
>   create mode 100644 drivers/net/ethernet/mellanox/mlx5/core/sf/devlink.c
>   create mode 100644 drivers/net/ethernet/mellanox/mlx5/core/sf/hw_table.c
>   create mode 100644 drivers/net/ethernet/mellanox/mlx5/core/sf/mlx5_ifc_vhca_event.h
>   create mode 100644 drivers/net/ethernet/mellanox/mlx5/core/sf/priv.h
>   create mode 100644 drivers/net/ethernet/mellanox/mlx5/core/sf/sf.h
>   create mode 100644 drivers/net/ethernet/mellanox/mlx5/core/sf/vhca_event.c
>   create mode 100644 drivers/net/ethernet/mellanox/mlx5/core/sf/vhca_event.h
>

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