[PATCH net-next v4 0/6] Add new PCP and APPTRUST attributes to dcbnl

Daniel Machon
2022-10-28T09:55:08Z

This patch series adds new extension attributes to dcbnl, to support PCP
prioritization (and thereby hw offloadable pcp-based queue
classification) and per-selector trust and trust order. Additionally,
the microchip sparx5 driver has been dcb-enabled to make use of the new
attributes to offload PCP, DSCP and Default prio to the switch, and
implement trust order of selectors.

For pre-RFC discussion see:
https://lore.kernel.org/netdev/Yv9VO1DYAxNduw6A@DEN-LT-70577/

For RFC series see:
https://lore.kernel.org/netdev/20220915095757.2861822-1-daniel.machon@microchip.com/

In summary: there currently exist no convenient way to offload per-port
PCP-based queue classification to hardware. The DCB subsystem offers
different ways to prioritize through its APP table, but lacks an option
for PCP. Similarly, there is no way to indicate the notion of trust for
APP table selectors. This patch series addresses both topics.

PCP based queue classification:
- 8021Q standardizes the Priority Code Point table (see 6.9.3 of IEEE
Std 802.1Q-2018). This patch series makes it possible, to offload
the PCP classification to said table. The new PCP selector is not a
standard part of the APP managed object, therefore it is
encapsulated in a new non-std extension attribute.

Selector trust:
- ASIC's often has the notion of trust DSCP and trust PCP. The new
attribute makes it possible to specify a trust order of app
selectors, which drivers can then react on.

DCB-enable sparx5 driver:
- Now supports offloading of DSCP, PCP and default priority. Only one
mapping of protocol:priority is allowed. Consecutive mappings of the
same protocol to some new priority, will overwrite the previous. This
is to keep a consistent view of the app table and the hardware.
- Now supports dscp and pcp trust, by use of the introduced
dcbnl_set/getapptrust ops. Sparx5 supports trust orders: [], [dscp],
[pcp] and [dscp, pcp]. For now, only DSCP and PCP selectors are
supported by the driver, everything else is bounced.

Patch #1 introduces a new PCP selector to the APP object, which makes it
possible to encode PCP and DEI in the app triplet and offload it to the
PCP table of the ASIC.

Patch #2 Introduces the new extension attributes
DCB_ATTR_DCB_APP_TRUST_TABLE and DCB_ATTR_DCB_APP_TRUST. Trusted
selectors are passed in the nested DCB_ATTR_DCB_APP_TRUST_TABLE
attribute, and assembled into an array of selectors:

u8 selectors[256];

where lower indexes has higher precedence. In the array, selectors are
stored consecutively, starting from index zero. With a maximum number of
256 unique selectors, the list has the same maximum size.

Patch #3 Sets up the dcbnl ops hook, and adds support for offloading pcp
app entries, to the PCP table of the switch.

Patch #4 Makes use of the dcbnl_set/getapptrust ops, to set a per-port
trust order.

Patch #5 Adds support for offloading dscp app entries to the DSCP table
of the switch.

Patch #6 Adds support for offloading default prio app entries to the
switch.

================================================================================

RFC v1:
https://lore.kernel.org/netdev/20220908120442.3069771-1-daniel.machon@microchip.com/

RFC v1 -> RFC v2:
- Added new nested attribute type DCB_ATTR_DCB_APP_TRUST_TABLE.
- Renamed attributes from DCB_ATTR_IEEE_* to DCB_ATTR_DCB_*.
- Renamed ieee_set/getapptrust to dcbnl_set/getapptrust.
- Added -EOPNOTSUPP if dcbnl_setapptrust is not set.
- Added sanitization of selector array, before passing to driver.

RFC v2 -> (non-RFC) v1:
- Added additional check for selector validity.
- Fixed a few style errors.
- using nla_start_nest() instead of nla_start_nest_no_flag().
- Moved DCB_ATTR_DCB_APP_TRUST into new enum.
- Added new DCB_ATTR_DCB_APP extension attribute, for non-std selector
values.
- Added support for offloading dscp, pcp and default prio in the sparx5
driver.
- Added support for per-selector trust and trust order in the sparx5
driver.

v1 -> v2:
- Fixed compiler and kdoc warning

v2 -> v3:
- Moved back to 255 as PCP selector value.
- Fixed return value in dcbnl_app_attr_type_get() to enum.
- Modified in dcbnl_app_attr_type_get() dcbnl_app_attr_type_validate() to
return directly.
- Added nselector check in sparx5_dcb_apptrust_validate().
- Added const qualifier to "names" variable in struct sparx5_dcb_apptrust.
- Added new SPARX5_DCB config. Fixes issues reported by kernel test robot.

v3 -> v4:
- Added new dcbnl_app_attr_selector_validate() function to validate that
app selectors are sent in correct attribute e.g IEEE selectors in
DCB_ATTR_IEEE and non-std selectors in DCB_ATTR_DCB.
- Modified handling of dcbnl_getapptrust() return value, so that an error is
ignored. Instead, added error check on nla_put_u8() and cancelling nest in
case of an error.

Daniel Machon (6):
net: dcb: add new pcp selector to app object
net: dcb: add new apptrust attribute
net: microchip: sparx5: add support for offloading pcp table
net: microchip: sparx5: add support for apptrust
net: microchip: sparx5: add support for offloading dscp table
net: microchip: sparx5: add support for offloading default prio

drivers/net/ethernet/microchip/sparx5/Kconfig | 10 +
.../net/ethernet/microchip/sparx5/Makefile | 2 +
.../ethernet/microchip/sparx5/sparx5_dcb.c | 293 ++++++++++++++++++
.../ethernet/microchip/sparx5/sparx5_main.h | 11 +
.../microchip/sparx5/sparx5_main_regs.h | 127 +++++++-
.../ethernet/microchip/sparx5/sparx5_port.c | 99 ++++++
.../ethernet/microchip/sparx5/sparx5_port.h | 37 +++
.../ethernet/microchip/sparx5/sparx5_qos.c | 4 +
include/net/dcbnl.h | 4 +
include/uapi/linux/dcbnl.h | 16 +
net/dcb/dcbnl.c | 159 +++++++++-
11 files changed, 753 insertions(+), 9 deletions(-)
create mode 100644 drivers/net/ethernet/microchip/sparx5/sparx5_dcb.c

--
2.34.1