i40e: don't report link up for a VF who hasn't enabled queues

Commit d3d657a ("i40e: update VFs of link state after
GET_VF_RESOURCES") modified the PF driver to notify a VF of
its link status immediately after it requests resources.

This was intended to fix reporting on VF drivers, so that they would
properly report link status.

However, some older VF drivers do not respond well to receiving a link
up notification before queues are enabled. This can cause their state
machine to think that it is safe to send traffic. This results in a Tx
hang on the VF.

More recent versions of the old i40evf and all versions of iavf are
resilient to these early link status messages. However, if a VM happens
to run an older version of the VF driver, this can be problematic.

Record whether the PF has actually enabled queues for the VF. When
reporting link status, always report link down if the queues aren't
enabled. In this way, the VF driver will never receive a link up
notification until after its queues are enabled.

Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

drivers/net/ethernet/intel/i40e/i40e_virtchnl_pf.c

@@ -55,7 +55,12 @@ static void i40e_vc_notify_vf_link_state(struct i40e_vf *vf)
 
 	pfe.event = VIRTCHNL_EVENT_LINK_CHANGE;
 	pfe.severity = PF_EVENT_SEVERITY_INFO;
-	if (vf->link_forced) {
+
+	/* Always report link is down if the VF queues aren't enabled */
+	if (!vf->queues_enabled) {
+		pfe.event_data.link_event.link_status = false;
+		pfe.event_data.link_event.link_speed = 0;
+	} else if (vf->link_forced) {
 		pfe.event_data.link_event.link_status = vf->link_up;
 		pfe.event_data.link_event.link_speed =
 			(vf->link_up ? VIRTCHNL_LINK_SPEED_40GB : 0);
@@ -65,6 +70,7 @@ static void i40e_vc_notify_vf_link_state(struct i40e_vf *vf)
 		pfe.event_data.link_event.link_speed =
 			i40e_virtchnl_link_speed(ls->link_speed);
 	}
+
 	i40e_aq_send_msg_to_vf(hw, abs_vf_id, VIRTCHNL_OP_EVENT,
 			       0, (u8 *)&pfe, sizeof(pfe), NULL);
 }
@@ -2364,6 +2370,8 @@ static int i40e_vc_enable_queues_msg(struct i40e_vf *vf, u8 *msg)
 		}
 	}
 
+	vf->queues_enabled = true;
+
 error_param:
 	/* send the response to the VF */
 	return i40e_vc_send_resp_to_vf(vf, VIRTCHNL_OP_ENABLE_QUEUES,
@@ -2385,6 +2393,9 @@ static int i40e_vc_disable_queues_msg(struct i40e_vf *vf, u8 *msg)
 	struct i40e_pf *pf = vf->pf;
 	i40e_status aq_ret = 0;
 
+	/* Immediately mark queues as disabled */
+	vf->queues_enabled = false;
+
 	if (!test_bit(I40E_VF_STATE_ACTIVE, &vf->vf_states)) {
 		aq_ret = I40E_ERR_PARAM;
 		goto error_param;

drivers/net/ethernet/intel/i40e/i40e_virtchnl_pf.h

@@ -99,6 +99,7 @@ struct i40e_vf {
 	unsigned int tx_rate;	/* Tx bandwidth limit in Mbps */
 	bool link_forced;
 	bool link_up;		/* only valid if VF link is forced */
+	bool queues_enabled;	/* true if the VF queues are enabled */
 	bool spoofchk;
 	u16 num_mac;
 	u16 num_vlan;