i40e: Fix attach VF to VM issue

Fix for "Resource temporarily unavailable" problem when virsh is
trying to attach a device to VM. When the VF driver is loaded on
host and virsh is trying to attach it to the VM and set a MAC
address, it ends with a race condition between i40e_reset_vf and
i40e_ndo_set_vf_mac functions. The bug is fixed by adding polling
in i40e_ndo_set_vf_mac function For when the VF is in Reset mode.

Signed-off-by: Paweł Jabłoński <pawel.jablonski@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

@@ -3741,6 +3741,7 @@ int i40e_ndo_set_vf_mac(struct net_device *netdev, int vf_id, u8 *mac)
 	int ret = 0;
 	struct hlist_node *h;
 	int bkt;
+	u8 i;
 
 	/* validate the request */
 	if (vf_id >= pf->num_alloc_vfs) {
@@ -3752,6 +3753,16 @@ int i40e_ndo_set_vf_mac(struct net_device *netdev, int vf_id, u8 *mac)
 
 	vf = &(pf->vf[vf_id]);
 	vsi = pf->vsi[vf->lan_vsi_idx];
+
+	/* When the VF is resetting wait until it is done.
+	 * It can take up to 200 milliseconds,
+	 * but wait for up to 300 milliseconds to be safe.
+	 */
+	for (i = 0; i < 15; i++) {
+		if (test_bit(I40E_VF_STATE_INIT, &vf->vf_states))
+			break;
+		msleep(20);
+	}
 	if (!test_bit(I40E_VF_STATE_INIT, &vf->vf_states)) {
 		dev_err(&pf->pdev->dev, "VF %d still in reset. Try again.\n",
 			vf_id);