RE: [PATCH 5/5] net/iavf: improve VF reset detection on fast ARQ flip

> Subject: [PATCH 5/5] net/iavf: improve VF reset detection on fast ARQ flip
> 
> During PF-initiated reset or a remote/ToR switch link-flap,
> the PF toggles the admin receive queue enable bit (ARQLEN1)
> so quickly around a VF reset that the VF's sampling window
> misses it, leaving the PF and the VF states out of sync
> and the data path stalled.
> 
> Complement the ARQLEN1 check with VFGEN_RSTAT
> (VIRTCHNL_VFR_INPROGRESS) and shorten the poll interval to
> 5 ms (with a proportionally larger count, keeping the ~10 s
> budget), matching the Linux kernel iavf driver.
> When the VFR is still not observed, proceed with recovery
> instead of bailing out so the PF and  the VF states converge.
> 
> Fixes: ada64daa1a5b ("net/iavf: fix VF reset for flow director rule")
> Fixes: 80fb3c920458 ("net/iavf: fix crash on VF start")
> Cc: [email protected]
> 
> Signed-off-by: Anurag Mandal <[email protected]>
> ---
>  drivers/net/intel/iavf/iavf.h        |  1 +
>  drivers/net/intel/iavf/iavf_ethdev.c | 41 +++++++++++++++++++++-------
>  2 files changed, 32 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/net/intel/iavf/iavf.h b/drivers/net/intel/iavf/iavf.h
> index 037bc8436f..5e49e81447 100644
> --- a/drivers/net/intel/iavf/iavf.h
> +++ b/drivers/net/intel/iavf/iavf.h
> @@ -21,6 +21,7 @@
>  #define IAVF_AQ_BUF_SZ            4096
>  #define IAVF_RESET_WAIT_CNT       2000
>  #define IAVF_RESET_DETECTED_CNT   500
> +#define IAVF_RESET_POLL_SCALE     4  /* Poll-interval scale for reset detection
> */
>  #define IAVF_BUF_SIZE_MIN         1024
>  #define IAVF_FRAME_SIZE_MAX       9728
>  #define IAVF_QUEUE_BASE_ADDR_UNIT 128
> diff --git a/drivers/net/intel/iavf/iavf_ethdev.c
> b/drivers/net/intel/iavf/iavf_ethdev.c
> index f6ce339b0c..21bac51467 100644
> --- a/drivers/net/intel/iavf/iavf_ethdev.c
> +++ b/drivers/net/intel/iavf/iavf_ethdev.c
> @@ -3235,7 +3235,9 @@ iavf_dev_close(struct rte_eth_dev *dev)
>  	/* remove RSS configuration */
>  	iavf_hash_uninit(adapter);
> 
> -	iavf_flow_flush(dev, NULL);
> +	/* Skip the virtchnl-emitting teardown on a PF-initiated reset */
> +	if (!vf->pf_reset_in_progress)
> +		iavf_flow_flush(dev, NULL);

This seems like a valid change but unrelated to the rest of the commit.
Consider splitting it out.

>  	iavf_flow_uninit(adapter);
> 
>  	/*
> @@ -3358,8 +3360,26 @@ iavf_dev_reset(struct rte_eth_dev *dev)
>  static inline bool
>  iavf_is_reset(struct iavf_hw *hw)
>  {
> -	return !(IAVF_READ_REG(hw, IAVF_VF_ARQLEN1) &
> -		IAVF_VF_ARQLEN1_ARQENABLE_MASK);
> +	uint32_t rstat;
> +
> +	/* ARQ has been disabled by the PF as part of the VFR. */
> +	if (!(IAVF_READ_REG(hw, IAVF_VF_ARQLEN1) &
> +		IAVF_VF_ARQLEN1_ARQENABLE_MASK))
> +		return true;
> +
> +	/*
> +	 * VFGEN_RSTAT reports VIRTCHNL_VFR_INPROGRESS.
> +	 * At times, the PF flips ARQENABLE so quickly
> +	 * around a VFR that the ARQLEN1 sample window
> +	 * misses it. Using VFGEN_RSTAT, as a
> +	 * complementary indicator, prevents from
> +	 * missing a reset that really did happen.
> +	 */
> +	rstat = (IAVF_READ_REG(hw, IAVF_VFGEN_RSTAT) &
> +		 IAVF_VFGEN_RSTAT_VFR_STATE_MASK) >>
> +		IAVF_VFGEN_RSTAT_VFR_STATE_SHIFT;
> +
> +	return rstat == VIRTCHNL_VFR_INPROGRESS;
>  }
> 
>  static bool
> @@ -3368,11 +3388,14 @@ iavf_is_reset_detected(struct iavf_adapter
> *adapter)
>  	struct iavf_hw *hw = IAVF_DEV_PRIVATE_TO_HW(adapter);
>  	int i;
> 
> -	/* poll until we see the reset actually happen */
> -	for (i = 0; i < IAVF_RESET_DETECTED_CNT; i++) {
> +	/*
> +	 * Poll until the reset actually happen.
> +	 * Poll every 5 ms to catch the fast ARQ flips.
> +	 */
> +	for (i = 0; i < IAVF_RESET_DETECTED_CNT * IAVF_RESET_POLL_SCALE;
> i++) {
>  		if (iavf_is_reset(hw))
>  			return true;
> -		rte_delay_ms(20);
> +		rte_delay_us(5000);
>  	}
> 
>  	return false;
> @@ -3423,10 +3446,8 @@ iavf_handle_hw_reset(struct rte_eth_dev *dev,
> bool vf_initiated_reset)
>  		if (!dev->data->dev_started)
>  			return;
> 
> -		if (!iavf_is_reset_detected(adapter)) {
> -			PMD_DRV_LOG(DEBUG, "reset not start");
> -			return;
> -		}
> +		if (!iavf_is_reset_detected(adapter))
> +			PMD_DRV_LOG(WARNING, "VFR not observed;
> recovering anyway");
>  	}
> 
>  	vf->in_reset_recovery = true;
> --
> 2.34.1