From: Amos Kong <ak...@redhat.com>

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.

Signed-off-by: Amos Kong <ak...@redhat.com>
---
 drivers/net/virtio_net.c        | 21 ++++++++++++++++++++-
 include/uapi/linux/virtio_net.h |  8 +++++++-
 2 files changed, 27 insertions(+), 2 deletions(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 395ab4f..837c978 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -802,14 +802,32 @@ static int virtnet_set_mac_address(struct net_device 
*dev, void *p)
        struct virtnet_info *vi = netdev_priv(dev);
        struct virtio_device *vdev = vi->vdev;
        int ret;
+       struct scatterlist sg;
+       char save_addr[ETH_ALEN];
+       unsigned char save_aatype;
+
+       memcpy(save_addr, dev->dev_addr, ETH_ALEN);
+       save_aatype = dev->addr_assign_type;
 
        ret = eth_mac_addr(dev, p);
        if (ret)
                return ret;
 
-       if (virtio_has_feature(vdev, VIRTIO_NET_F_MAC))
+       if (virtio_has_feature(vdev, VIRTIO_NET_F_CTRL_MAC_ADDR)) {
+               sg_init_one(&sg, dev->dev_addr, dev->addr_len);
+               if (!virtnet_send_command(vi, VIRTIO_NET_CTRL_MAC,
+                                         VIRTIO_NET_CTRL_MAC_ADDR_SET,
+                                         &sg, 1, 0)) {
+                       dev_warn(&vdev->dev,
+                                "Failed to set mac address by vq command.\n");
+                       memcpy(dev->dev_addr, save_addr, ETH_ALEN);
+                       dev->addr_assign_type = save_aatype;
+                       return -EINVAL;
+               }
+       } else if (virtio_has_feature(vdev, VIRTIO_NET_F_MAC)) {
                vdev->config->set(vdev, offsetof(struct virtio_net_config, mac),
                                  dev->dev_addr, dev->addr_len);
+       }
 
        return 0;
 }
@@ -1627,6 +1645,7 @@ static unsigned int features[] = {
        VIRTIO_NET_F_MRG_RXBUF, VIRTIO_NET_F_STATUS, VIRTIO_NET_F_CTRL_VQ,
        VIRTIO_NET_F_CTRL_RX, VIRTIO_NET_F_CTRL_VLAN,
        VIRTIO_NET_F_GUEST_ANNOUNCE, VIRTIO_NET_F_MQ,
+       VIRTIO_NET_F_CTRL_MAC_ADDR,
 };
 
 static struct virtio_driver virtio_net_driver = {
diff --git a/include/uapi/linux/virtio_net.h b/include/uapi/linux/virtio_net.h
index 848e358..a5a8c88 100644
--- a/include/uapi/linux/virtio_net.h
+++ b/include/uapi/linux/virtio_net.h
@@ -53,6 +53,7 @@
                                         * network */
 #define VIRTIO_NET_F_MQ        22      /* Device supports Receive Flow
                                         * Steering */
+#define VIRTIO_NET_F_CTRL_MAC_ADDR 23  /* Set MAC address */
 
 #define VIRTIO_NET_S_LINK_UP   1       /* Link is up */
 #define VIRTIO_NET_S_ANNOUNCE  2       /* Announcement is needed */
@@ -127,7 +128,7 @@ typedef __u8 virtio_net_ctrl_ack;
  #define VIRTIO_NET_CTRL_RX_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
@@ -140,6 +141,10 @@ typedef __u8 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 {
        __u32 entries;
@@ -148,6 +153,7 @@ 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
-- 
1.7.11.7


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