APPLIED[Q/P/N/J]: [SRU][R/Q/P/N/J][PATCH 0/1] i40e: avoid redundant VF link state updates

[Stefan Bader]

On 11/11/2025 14:29, Stefan Bader wrote:
> On 03/11/2025 16:40, Robert Malz wrote:
>> BugLink: https://bugs.launchpad.net/bugs/2130552
>>
>> [ Impact ]
>>
>>   * In the i40e driver, every VF link state change request is causing 
>> a VF reset,
>>     even if the requested change is already set. This leads to 
>> unnecessary VF
>>     resets and can cause performance degradation or instability in the VF
>>     driver, particularly in DPDK environments.
>>
>>   * With the proposed patch, i40e will skip VF link state change 
>> requests when the
>>     desired link state matches the current configuration. This prevents
>>     unnecessary VF resets and reduces PF-VF communication overhead.
>>
>>   * The issue was originally detected by analyzing DPDK VF driver 
>> issues during
>>     OpenStack Neutron restarts. In such cases, i40e will issue an 
>> unnecessary VF
>>     reset request which causes instability in the DPDK driver.
>>
>> [ Test Plan ]
>>
>>   * The issue can be reproduced by triggering VF link state changes 
>> multiple times
>>     with the same requested link state.
>>
>>   * To reproduce the problem, run the following command multiple times
>>     on the same interface: 'ip link set <ifname> vf 0 state auto'.
>>     Every time the command is executed, the PF driver will trigger a 
>> VF reset.
>>
>>   * Monitor for VF reset events using dmesg or appropriate logging 
>> mechanisms
>>     to confirm the issue and verify the fix.
>>
>>   * Regression testing should include:
>>     - Verify normal VF link state changes still work correctly when 
>> state actually changes
>>     - Validate that legitimate state changes still trigger resets when 
>> needed
>>
>> [ Where problems could occur ]
>>
>>   * Changes only affect the i40e .ndo_set_vf_link_state routine. In case
>>     of any regressions, only the ability to set VF link state changes 
>> could be
>>     impacted.
>>
>>   * The patch was verified locally and passed Intel internal test 
>> execution.
>>
>>   * Potential failure modes:
>>     - Logic error in state comparison could prevent legitimate state 
>> changes
>>     - Incorrect state tracking could lead to inconsistent VF behavior
>>
>>   * Risk mitigation:
>>     - The change is isolated to a specific code path in the i40e driver
>>     - Existing VF functionality remains unchanged when state changes 
>> are needed
>>     - The patch adds a simple comparison check before existing link 
>> change routine
>>
>> [ Other Info ]
>>
>>   * At the time of writing this document, the target patch is still in 
>> the net-next
>>     tree and has not yet been merged into linux-next.
>>
>>   * Patch: a7ae783da0b919550e260aebfca1c6ef030b99a4 from netdev/net-next
>>
>>   * Patch applies on most versions without any conflicts
>>
>>   * No dependencies on other patches
>>
>>   * Backport requirements: Patch should apply cleanly to Ubuntu kernel 
>> versions
>>
>>   * VF reset during link state change was added as a part of 
>> 31deb12e85c35ddd2c037f0107d05d8674cab2c0 (upstream) commit, which is 
>> included in the Kernels starting from 5.15
>>
>> Jay Vosburgh (1):
>>    i40e: avoid redundant VF link state updates
>>
>>   drivers/net/ethernet/intel/i40e/i40e_virtchnl_pf.c | 12 ++++++++++++
>>   1 file changed, 12 insertions(+)
>>
> 
> 
> Applied to questing,plucky,noble,jammy:linux/master-next (to be included 
> in s2025.10.13). Thanks.

Wanted to add that I changed net-next to linux-next as it landed there 
by now (same SHA1).

> 
> -Stefan
> 

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