Re: [PATCH net 5/6] iavf: fix VF stats not updating due to PTP command preemption

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- [Medium] iavf_watchdog_step()
  (drivers/net/ethernet/intel/iavf/iavf_main.c) now calls…

--

iavf: fix VF stats not updating due to PTP command preemption

With this commit, iavf_watchdog_step() requests VF stats on every pass
while the adapter is in __IAVF_RUNNING. Before, it only did so when
iavf_process_aq_command() found nothing to do. The periodic PHC caching
task keeps a PTP command pending, so the old stats fallback never ran.

> diff --git a/drivers/net/ethernet/intel/iavf/iavf_main.c b/drivers/net/ethernet/intel/iavf/iavf_main.c
> index 29b8403a066bc..c0686ad5c4116 100644
> --- a/drivers/net/ethernet/intel/iavf/iavf_main.c
> +++ b/drivers/net/ethernet/intel/iavf/iavf_main.c
> @@ -2932,18 +2932,12 @@ static int iavf_watchdog_step(struct iavf_adapter *adapter)
>  				iavf_send_api_ver(adapter);
>  			}
>  		} else {
> -			int ret = iavf_process_aq_command(adapter);
> -
> -			/* An error will be returned if no commands were
> -			 * processed; use this opportunity to update stats
> -			 * if the error isn't -ENOTSUPP
> -			 */
> -			if (ret && ret != -EOPNOTSUPP &&
> -			    adapter->state == __IAVF_RUNNING)
> -				iavf_request_stats(adapter);
> +			iavf_process_aq_command(adapter);
>  		}
> -		if (adapter->state == __IAVF_RUNNING)
> +		if (adapter->state == __IAVF_RUNNING) {
> +			iavf_request_stats(adapter);

[Severity: Medium]
Can this put two virtchnl messages in flight during one watchdog pass?

Suppose iavf_process_aq_command() has just taken the
IAVF_FLAG_AQ_SEND_PTP_CMD branch. In that case
iavf_virtchnl_send_ptp_cmd() has sent VIRTCHNL_OP_1588_PTP_GET_TIME
without setting adapter->current_op:

iavf_virtchnl.c:iavf_virtchnl_send_ptp_cmd() {
    ...
	err = iavf_send_pf_msg(adapter, cmd->v_opcode, cmd->msg, cmd->msglen);
	if (!err) {
		list_del(&cmd->list);
		kfree(cmd);
    ...
}

The only guard in iavf_request_stats() then still sees an idle channel,
so VIRTCHNL_OP_GET_STATS goes out right behind GET_TIME:

	if (adapter->current_op != VIRTCHNL_OP_UNKNOWN) {
		/* no error message, this isn't crucial */
		return;
	}
	...
	adapter->current_op = VIRTCHNL_OP_GET_STATS;

When the GET_TIME reply arrives, iavf_virtchnl_completion() breaks out
of the switch and reaches the unconditional reset at the end:

	} /* switch v_opcode */
	adapter->current_op = VIRTCHNL_OP_UNKNOWN;

That clears the GET_STATS tracking while the GET_STATS reply is still
outstanding.

iavf_adminq_task() may drop the netdev lock before the GET_STATS reply
arrives. A watchdog pass can then send another tracked command. The
watchdog can be kicked by iavf_schedule_aq_request(), by the 20ms re-arm
while aq_required is set, or by gettimex64() queuing another PTP read
with mod_delayed_work(..., 0). The late GET_STATS reply would then clear
that command's current_op as well.

Flow Director is one place where this could do real damage.
iavf_add_fdir_filter() relies on current_op to keep only one
ADD_PENDING filter in flight. If two adds overlap, the first successful
VIRTCHNL_OP_ADD_FDIR_FILTER reply does this for every pending filter:

			if (fdir->state == IAVF_FDIR_FLTR_ADD_PENDING) {
				if (add_fltr->status == VIRTCHNL_FDIR_SUCCESS) {
					...
					fdir->state = IAVF_FDIR_FLTR_ACTIVE;
					fdir->flow_id = add_fltr->flow_id;

Would the second filter then get the wrong PF flow_id? If so, a later
delete of that filter could remove the wrong PF rule and leak the real
one.

The missing current_op tracking in the PTP sender predates this patch.
Before this change, though, GET_STATS was only sent in a pass where
iavf_process_aq_command() returned an error, so it never followed a PTP
message back to back. Now every PTP send is followed by a GET_STATS in
the same pass. That covers the roughly once-per-second PHC cache update
and every gettimex64() read.

This also adds one GET_STATS mailbox message per PHC read, which the
commit message doesn't mention.

>  			iavf_detect_recover_hung(&adapter->vsi);
> +		}
>  		break;

[ ... ]

-- 
Sashiko AI review · https://netdev-ai.bots.linux.dev/sashiko/#/patchset/20260928230429.495442-1-anthony.l.nguyen%40intel.com