On Thu, Nov 13, 2025 at 01:33:43PM -0800, Jacob Keller wrote: > In certain cases, the PF for the iavf driver may support > VIRTCHNL_VF_CAP_PTP but will not enable Rx timestamps. If this occurs, the > iavf driver will attempt to continue anyways. When that happens, the > resulting timestamps will appear to function initially. Upon closer > inspection it becomes clear that the timestamps are invalid and bogus. > > First, when reporting a timestamp, always check the validity bit instead of > blindly reporting it. This avoids extending an invalid (likely zero'd) > timestamp value from the Rx descriptor. > > Second, don't enable the RTE_ETH_RX_OFFLOAD_TIMESTAMP capability if the PF > doesn't indicate we have support. This will prevent applications from > trying to timestamp when it is not properly enabled. > > Typically, this should not happen, as the PFs which support > VIRTCHNL_VF_CAP_PTP should support Rx timestamping. However, we recently > discovered a flaw in some implementations of the > VIRTCHNL_OP_1588_PTP_GET_CAPS command. The layout of the capabilities > structure is incorrect, with the caps member placed at a different byte > offset than the expected structure layout. This is the case with the > upstream Linux ice PF driver. > > This results in the PF rejecting the request for Rx timestamping, and > leaving timestamping disabled. A proper fix for this situation is > difficult. If we merely changed the structure layout in DPDK, then it would > stop being compatible with other host OSes and with other implementations > of the Linux ice PF. If we changed the layout upstream, it would break > compatibility with the upstream iAVF VF driver. > > A proper fix to resolve this will take some time, as we will likely have to > introduce a new flag or ops capability across many drivers. In the mean > time, we should at least make sure the DPDK driver stops reporting bogus > timestamps in such a setup. > > Signed-off-by: Jacob Keller <[email protected]> > --- > Jacob Keller (2): > net/iavf: check if PF actually indicates Rx timestamps > net/iavf: check Rx timestamp validity bit > Series applied to dpdk-next-net-intel.
Thanks, /Bruce
