virtio-net: introduce a new macaddr control

In virtio-net guest driver, currently we write MAC address to
pci config space byte by byte, this means that we have an
intermediate step where mac is wrong. This patch introduced
a new control command to set MAC address, it's atomic.

VIRTIO_NET_F_CTRL_MAC_ADDR is a new feature bit for compatibility.

"mac" field will be set to read-only when VIRTIO_NET_F_CTRL_MAC_ADDR
is acked.
Signed-off-by: NAmos Kong <akong@redhat.com>
Signed-off-by: NMichael S. Tsirkin <mst@redhat.com>

hw/pc_piix.c

@@ -309,6 +309,10 @@ static QEMUMachine pc_i440fx_machine_v1_4 = {
             .driver   = "usb-tablet",\
             .property = "usb_version",\
             .value    = stringify(1),\
+        },{\
+            .driver   = "virtio-net-pci",\
+            .property = "ctrl_mac_addr",\
+            .value    = "off",      \
         }
 
 static QEMUMachine pc_machine_v1_3 = {

hw/virtio-net.c

@@ -93,7 +93,8 @@ static void virtio_net_set_config(VirtIODevice *vdev, const uint8_t *config)
 
     memcpy(&netcfg, config, sizeof(netcfg));
 
-    if (memcmp(netcfg.mac, n->mac, ETH_ALEN)) {
+    if (!(n->vdev.guest_features >> VIRTIO_NET_F_CTRL_MAC_ADDR & 1) &&
+        memcmp(netcfg.mac, n->mac, ETH_ALEN)) {
         memcpy(n->mac, netcfg.mac, ETH_ALEN);
         qemu_format_nic_info_str(&n->nic->nc, n->mac);
     }
@@ -351,6 +352,16 @@ static int virtio_net_handle_mac(VirtIONet *n, uint8_t cmd,
     struct virtio_net_ctrl_mac mac_data;
     size_t s;
 
+    if (cmd == VIRTIO_NET_CTRL_MAC_ADDR_SET) {
+        if (iov_size(iov, iov_cnt) != sizeof(n->mac)) {
+            return VIRTIO_NET_ERR;
+        }
+        s = iov_to_buf(iov, iov_cnt, 0, &n->mac, sizeof(n->mac));
+        assert(s == sizeof(n->mac));
+        qemu_format_nic_info_str(&n->nic->nc, n->mac);
+        return VIRTIO_NET_OK;
+    }
+
     if (cmd != VIRTIO_NET_CTRL_MAC_TABLE_SET) {
         return VIRTIO_NET_ERR;
     }

hw/virtio-net.h

@@ -44,6 +44,8 @@
 #define VIRTIO_NET_F_CTRL_VLAN  19      /* Control channel VLAN filtering */
 #define VIRTIO_NET_F_CTRL_RX_EXTRA 20   /* Extra RX mode control support */
 
+#define VIRTIO_NET_F_CTRL_MAC_ADDR   23 /* Set MAC address */
+
 #define VIRTIO_NET_S_LINK_UP    1       /* Link is up */
 
 #define TX_TIMER_INTERVAL 150000 /* 150 us */
@@ -106,7 +108,7 @@ typedef uint8_t virtio_net_ctrl_ack;
  #define VIRTIO_NET_CTRL_RX_MODE_NOBCAST      5
 
 /*
- * Control the MAC filter table.
+ * Control the MAC
  *
  * The MAC filter table is managed by the hypervisor, the guest should
  * assume the size is infinite.  Filtering should be considered
@@ -119,6 +121,10 @@ typedef uint8_t virtio_net_ctrl_ack;
  * first sg list contains unicast addresses, the second is for multicast.
  * This functionality is present if the VIRTIO_NET_F_CTRL_RX feature
  * is available.
+ *
+ * The ADDR_SET command requests one out scatterlist, it contains a
+ * 6 bytes MAC address. This functionality is present if the
+ * VIRTIO_NET_F_CTRL_MAC_ADDR feature is available.
  */
 struct virtio_net_ctrl_mac {
     uint32_t entries;
@@ -126,6 +132,7 @@ struct virtio_net_ctrl_mac {
 };
 #define VIRTIO_NET_CTRL_MAC    1
  #define VIRTIO_NET_CTRL_MAC_TABLE_SET        0
+ #define VIRTIO_NET_CTRL_MAC_ADDR_SET         1
 
 /*
  * Control VLAN filtering
@@ -158,5 +165,6 @@ struct virtio_net_ctrl_mac {
         DEFINE_PROP_BIT("ctrl_vq", _state, _field, VIRTIO_NET_F_CTRL_VQ, true), \
         DEFINE_PROP_BIT("ctrl_rx", _state, _field, VIRTIO_NET_F_CTRL_RX, true), \
         DEFINE_PROP_BIT("ctrl_vlan", _state, _field, VIRTIO_NET_F_CTRL_VLAN, true), \
-        DEFINE_PROP_BIT("ctrl_rx_extra", _state, _field, VIRTIO_NET_F_CTRL_RX_EXTRA, true)
+        DEFINE_PROP_BIT("ctrl_rx_extra", _state, _field, VIRTIO_NET_F_CTRL_RX_EXTRA, true), \
+        DEFINE_PROP_BIT("ctrl_mac_addr", _state, _field, VIRTIO_NET_F_CTRL_MAC_ADDR, true)
 #endif