[j:linux-intel-iotg][j:linux-intel-iot-realtime] Cannot set frame preemption

[Philip Cox]

This is a public version of https://bugs.launchpad.net/bugs/2034007

[Summary]
System cannot set frame preemption via the ethtool-rt from snap store[1], will got netlink error.

[1] https://snapcraft.io/ethtool-rt

u@u-Alder-Lake-Client-Platform:~$ sudo ethtool-rt.ethtool --set-frame-preemption enp1s0 fp on
netlink error: frame preemption settings update failed
netlink error: Invalid argument
u@u-Alder-Lake-Client-Platform:~$ echo $?
81
u@u-Alder-Lake-Client-Platform:~$ sudo ethtool-rt.ethtool --show-frame-preemption enp1s0
Frame preemption settings for enp1s0:
enabled: not enabled
additional fragment size: 0
verified: 0
verification disabled: 1

[Steps to reproduce]
1. sudo snap install ethtool-ty --devmode --edge
2.sudo ethtool-rt.ethtool --set-frame-preemption {your ethernet interface} fp on
3.sudo ethtool-rt.ethtool --show-frame-preemption {your ethernet interface}

[Expected result]
Set frame preemption successfully.

[Actual result]
Got netlink error.

[Failure rate]
3/3

[Additional information]
CID: 202305-31589
SKU: ADL-S
system-manufacturer: Intel Corporation
system-product-name: Alder Lake Client Platform
bios-version: RPLISFI1.R00.4081.A05.2305241419
CPU: 12th Gen Intel(R) Core(TM) i3-12100E (8x)
GPU: 00:02.0 VGA compatible controller [0300]: Intel Corporation Device [8086:4692] (rev 0c)
kernel-version: 5.15.0-1035-intel-iot-realtime

[Stage]
Issue reported and logs collected right after it happened

----------------------

Philip Cox (philcox) wrote on 2023-09-07:   #4
After going through the code, it looks like this is caused by the variable fpcmd->add_frag_size is set to 0 and in the function igc_ethtool_set_preempt() there is the following check:

if (fpcmd->add_frag_size < 68 || fpcmd->add_frag_size > 260)
 return -EINVAL;

And this is causing the the --set-frame-preemption to fail.

ubuntu@adl-p:~$ sudo ethtool-rt.ethtool --set-frame-preemption enp169s0 fp on ; echo $?
netlink error: frame preemption settings update failed
netlink error: Invalid argument
81
ubuntu@adl-p:~$

I see in igc.h that there is a #define for IGC_I225_MIN_FRAG_SIZE_DEFAULT which is:

#define IGC_I225_MIN_FRAG_SIZE_DEFAULT 68

This is set in igc_tsn_disable_offload()

static int igc_tsn_disable_offload(struct igc_adapter *adapter)
{
...
 adapter->cycle_time = 0;
 adapter->add_frag_size = IGC_I225_MIN_FRAG_SIZE_DEFAULT;
...
}

but igc_tsn_disable_offload is not called, so the value is never set.

---------------------

Lai Jun Ann (laijunann-intel) wrote 12 hours ago: #12
0001-igc-fix-frame-preemption-not-able-to-set.patch Edit (1.3 KiB, text/plain)
The patch is ready and uploaded. Below shows the testing done with the patch:
oot@ubuntu-Alder-Lake-Client-Platform:~# ethtool --show-frame-preemption enp1s0
Frame preemption settings for enp1s0:
        enabled: enabled
        additional fragment size: 68
        verified: 0
        verification disabled: 1
root@ubuntu-Alder-Lake-Client-Platform:~#
root@ubuntu-Alder-Lake-Client-Platform:~# ethtool --set-frame-preemption enp1s0 fp off
root@ubuntu-Alder-Lake-Client-Platform:~# ethtool --show-frame-preemption enp1s0
Frame preemption settings for enp1s0:
        enabled: not enabled
        additional fragment size: 68
        verified: 0
        verification disabled: 1
root@ubuntu-Alder-Lake-Client-Platform:~# ethtool --set-frame-preemption enp1s0 fp on
root@ubuntu-Alder-Lake-Client-Platform:~# ethtool --show-frame-preemption enp1s0
Frame preemption settings for enp1s0:
        enabled: enabled
        additional fragment size: 68
        verified: 0
        verification disabled: 1

--------------

Philip Cox (philcox) wrote 20 minutes ago:   #13
I've tested the patch as well, and it works. Thanks.

[Ubuntu Kernel Bot (ubuntu-kernel-bot)]

This bug is awaiting verification that the linux-intel-iotg/5.15.0-1044.50 kernel in -proposed solves the problem. Please test the kernel and update this bug with the results. If the problem is solved, change the tag 'verification-needed-jammy-linux-intel-iotg' to 'verification-done-jammy-linux-intel-iotg'. If the problem still exists, change the tag 'verification-needed-jammy-linux-intel-iotg' to 'verification-failed-jammy-linux-intel-iotg'.

If verification is not done by 5 working days from today, this fix will be dropped from the source code, and this bug will be closed.

See https://wiki.ubuntu.com/Testing/EnableProposed for documentation how to enable and use -proposed. Thank you!

[Launchpad Janitor (janitor)]

This bug was fixed in the package linux-intel-iotg - 5.15.0-1045.51

---------------
linux-intel-iotg (5.15.0-1045.51) jammy; urgency=medium

  * jammy/linux-intel-iotg: 5.15.0-1045.51 -proposed tracker (LP: #2041936)

  * Packaging resync (LP: #1786013)
    - [Packaging] resync git-ubuntu-log
    - [Packaging] resync update-dkms-versions helper

  [ Ubuntu: 5.15.0-89.99 ]

  * jammy/linux: 5.15.0-89.99 -proposed tracker (LP: #2041949)
  * CVE-2023-31085
    - ubi: Refuse attaching if mtd's erasesize is 0
  * CVE-2023-45871
    - igb: set max size RX buffer when store bad packet is enabled
  * CVE-2023-25775
    - RDMA/irdma: Remove irdma_uk_mw_bind()
    - RDMA/irdma: Remove irdma_sc_send_lsmm_nostag()
    - RDMA/irdma: Remove irdma_cqp_up_map_cmd()
    - RDMA/irdma: Remove irdma_get_hw_addr()
    - RDMA/irdma: Make irdma_uk_cq_init() return a void
    - RDMA/irdma: optimize rx path by removing unnecessary copy
    - RDMA/irdma: Remove enum irdma_status_code
    - RDMA/irdma: Remove excess error variables
    - RDMA/irdma: Prevent zero-length STAG registration
  * Packaging resync (LP: #1786013)
    - [Packaging] update helper scripts

 -- Philip Cox <email address hidden> Tue, 14 Nov 2023 15:45:39 -0500