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

[Stefan Bader]

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.

-Stefan

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