sfc: Change VF mac via PF as first preference if available.

Changing a VF's mac address through the VF (rather than via the PF)
fails with EPERM because the latter part of efx_ef10_set_mac_address
attempts to change the vport mac address list as the VF.
Even with this fixed it still fails with EBUSY because the vadaptor
is still assigned on the VF - the vadaptor reassignment must be within
a section where the VF has torn down its state.

A major reason this has broken is because we have two functions that
ostensibly do the same thing - have a PF and VF cooperate to change a
VF mac address. Rather than do this, if we are changing the mac of a VF
that has a link to the PF in the same VM then simply call
sriov_set_vf_mac instead, which is a proven working function that does
that.

If there is no PF available, or that fails non-fatally, then attempt to
change the VF's mac address as we would a PF, without updating the PF's
data.

Test case:
Create a VF:
echo 1 > /sys/class/net/<if>/device/sriov_numvfs
Set the mac address of the VF directly:
ip link set <vf> addr 00:11:22:33:44:55
Set the MAC address of the VF via the PF:
ip link set <pf> vf 0 mac 00:11:22:33:44:66
Without this patch the last command will fail with ENOENT.

Signed-off-by: Jonathan Cooper <[e-mail]>
Reported-by: Íñigo Huguet <[e-mail]>
Fixes: 910c8789a777 ("set the MAC address using MC_CMD_VADAPTOR_SET_MAC")
Acked-by: Edward Cree <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

drivers/net/ethernet/sfc/ef10.c

···
 	bool was_enabled = efx->port_enabled;
 	int rc;
 
+#ifdef CONFIG_SFC_SRIOV
+	/* If this function is a VF and we have access to the parent PF,
+	 * then use the PF control path to attempt to change the VF MAC address.
+	 */
+	if (efx->pci_dev->is_virtfn && efx->pci_dev->physfn) {
+		struct efx_nic *efx_pf = pci_get_drvdata(efx->pci_dev->physfn);
+		struct efx_ef10_nic_data *nic_data = efx->nic_data;
+		u8 mac[ETH_ALEN];
+
+		/* net_dev->dev_addr can be zeroed by efx_net_stop in
+		 * efx_ef10_sriov_set_vf_mac, so pass in a copy.
+		 */
+		ether_addr_copy(mac, efx->net_dev->dev_addr);
+
+		rc = efx_ef10_sriov_set_vf_mac(efx_pf, nic_data->vf_index, mac);
+		if (!rc)
+			return 0;
+
+		netif_dbg(efx, drv, efx->net_dev,
+			  "Updating VF mac via PF failed (%d), setting directly\n",
+			  rc);
+	}
+#endif
+
 	efx_device_detach_sync(efx);
 	efx_net_stop(efx->net_dev);
 
···
 		efx_net_open(efx->net_dev);
 	efx_device_attach_if_not_resetting(efx);
 
-#ifdef CONFIG_SFC_SRIOV
-	if (efx->pci_dev->is_virtfn && efx->pci_dev->physfn) {
-		struct efx_ef10_nic_data *nic_data = efx->nic_data;
-		struct pci_dev *pci_dev_pf = efx->pci_dev->physfn;
-
-		if (rc == -EPERM) {
-			struct efx_nic *efx_pf;
-
-			/* Switch to PF and change MAC address on vport */
-			efx_pf = pci_get_drvdata(pci_dev_pf);
-
-			rc = efx_ef10_sriov_set_vf_mac(efx_pf,
-						       nic_data->vf_index,
-						       efx->net_dev->dev_addr);
-		} else if (!rc) {
-			struct efx_nic *efx_pf = pci_get_drvdata(pci_dev_pf);
-			struct efx_ef10_nic_data *nic_data = efx_pf->nic_data;
-			unsigned int i;
-
-			/* MAC address successfully changed by VF (with MAC
-			 * spoofing) so update the parent PF if possible.
-			 */
-			for (i = 0; i < efx_pf->vf_count; ++i) {
-				struct ef10_vf *vf = nic_data->vf + i;
-
-				if (vf->efx == efx) {
-					ether_addr_copy(vf->mac,
-							efx->net_dev->dev_addr);
-					return 0;
-				}
-			}
-		}
-	} else
-#endif
 	if (rc == -EPERM) {
 		netif_err(efx, drv, efx->net_dev,
 			  "Cannot change MAC address; use sfboot to enable"