sfc: save old MAC address in case sriov_mac_address_changed fails

Otherwise the PF and VF can disagree on the VF's MAC address and
this leads to strange behaviour, up to and including kernel panics.
Signed-off-by: Shradha Shah <sshah@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/sfc/ef10_sriov.h

@@ -31,7 +31,10 @@ static inline bool efx_ef10_sriov_wanted(struct efx_nic *efx)
 
 int efx_ef10_sriov_configure(struct efx_nic *efx, int num_vfs);
 int efx_ef10_sriov_init(struct efx_nic *efx);
-static inline void efx_ef10_sriov_mac_address_changed(struct efx_nic *efx) {}
+static inline int efx_ef10_sriov_mac_address_changed(struct efx_nic *efx)
+{
+	return -EOPNOTSUPP;
+}
 static inline void efx_ef10_sriov_reset(struct efx_nic *efx) {}
 void efx_ef10_sriov_fini(struct efx_nic *efx);
 static inline void efx_ef10_sriov_flr(struct efx_nic *efx, unsigned vf_i) {}

drivers/net/ethernet/sfc/efx.c

@@ -2196,6 +2196,8 @@ static int efx_set_mac_address(struct net_device *net_dev, void *data)
 	struct efx_nic *efx = netdev_priv(net_dev);
 	struct sockaddr *addr = data;
 	u8 *new_addr = addr->sa_data;
+	u8 old_addr[6];
+	int rc;
 
 	if (!is_valid_ether_addr(new_addr)) {
 		netif_err(efx, drv, efx->net_dev,
@@ -2204,9 +2206,16 @@ static int efx_set_mac_address(struct net_device *net_dev, void *data)
 		return -EADDRNOTAVAIL;
 	}
 
+	/* save old address */
+	ether_addr_copy(old_addr, net_dev->dev_addr);
 	ether_addr_copy(net_dev->dev_addr, new_addr);
-	if (efx->type->sriov_mac_address_changed)
-		efx->type->sriov_mac_address_changed(efx);
+	if (efx->type->sriov_mac_address_changed) {
+		rc = efx->type->sriov_mac_address_changed(efx);
+		if (rc) {
+			ether_addr_copy(net_dev->dev_addr, old_addr);
+			return rc;
+		}
+	}
 
 	/* Reconfigure the MAC */
 	mutex_lock(&efx->mac_lock);

drivers/net/ethernet/sfc/net_driver.h

@@ -1334,7 +1334,7 @@ struct efx_nic_type {
 	int (*sriov_configure)(struct efx_nic *efx, int num_vfs);
 	int (*sriov_init)(struct efx_nic *efx);
 	void (*sriov_fini)(struct efx_nic *efx);
-	void (*sriov_mac_address_changed)(struct efx_nic *efx);
+	int (*sriov_mac_address_changed)(struct efx_nic *efx);
 	bool (*sriov_wanted)(struct efx_nic *efx);
 	void (*sriov_reset)(struct efx_nic *efx);
 	void (*sriov_flr)(struct efx_nic *efx, unsigned vf_i);

drivers/net/ethernet/sfc/siena_sriov.c

@@ -1476,16 +1476,18 @@ void efx_siena_sriov_flr(struct efx_nic *efx, unsigned vf_i)
 	vf->evq0_count = 0;
 }
 
-void efx_siena_sriov_mac_address_changed(struct efx_nic *efx)
+int efx_siena_sriov_mac_address_changed(struct efx_nic *efx)
 {
 	struct siena_nic_data *nic_data = efx->nic_data;
 	struct vfdi_status *vfdi_status = nic_data->vfdi_status.addr;
 
 	if (!efx->vf_init_count)
-		return;
+		return 0;
 	ether_addr_copy(vfdi_status->peers[0].mac_addr,
 			efx->net_dev->dev_addr);
 	queue_work(vfdi_workqueue, &nic_data->peer_work);
+
+	return 0;
 }
 
 void efx_siena_sriov_tx_flush_done(struct efx_nic *efx, efx_qword_t *event)

drivers/net/ethernet/sfc/siena_sriov.h

@@ -44,7 +44,7 @@
 int efx_siena_sriov_configure(struct efx_nic *efx, int num_vfs);
 int efx_siena_sriov_init(struct efx_nic *efx);
 void efx_siena_sriov_fini(struct efx_nic *efx);
-void efx_siena_sriov_mac_address_changed(struct efx_nic *efx);
+int efx_siena_sriov_mac_address_changed(struct efx_nic *efx);
 bool efx_siena_sriov_wanted(struct efx_nic *efx);
 void efx_siena_sriov_reset(struct efx_nic *efx);
 void efx_siena_sriov_flr(struct efx_nic *efx, unsigned flr);