[PATCH v4 5/7] net/iavf: improve VF reset detection on fast ARQ flip

[Anurag Mandal <anurag.mandal@intel.com>]

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: 80fb3c920458 ("net/iavf: fix crash on VF start")
Cc: stable@dpdk.org

Signed-off-by: Anurag Mandal <anurag.mandal@intel.com>
Acked-by: Ciara Loftus <ciara.loftus@intel.com>
---
 drivers/net/intel/iavf/iavf.h        |  1 +
 drivers/net/intel/iavf/iavf_ethdev.c | 37 +++++++++++++++++++++-------
 2 files changed, 29 insertions(+), 9 deletions(-)

diff --git a/drivers/net/intel/iavf/iavf.h b/drivers/net/intel/iavf/iavf.h
index 605e9dd3aa..d57040e630 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 0f5eb57bbe..322b59d68c 100644
--- a/drivers/net/intel/iavf/iavf_ethdev.c
+++ b/drivers/net/intel/iavf/iavf_ethdev.c
@@ -3358,8 +3358,26 @@ 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 +3386,14 @@ 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 +3444,8 @@ 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