Linux Virtualization - Jan 2013 - [PATCH v4 0/3] make mac programming for virtio net more robust

From: Amos Kong <akong at redhat.com>

Currenly mac is programmed byte by byte. This means that we
have an intermediate step where mac is wrong. 

Third patch introduced a new vq control command to set mac
address, it's atomic.

V2: check return of sending command, delay eth_mac_addr()
V3: restore software address when fail to set hardware address
V4: split eth_mac_addr, fix error handle

Amos Kong (2):
  move virtnet_send_command() above virtnet_set_mac_address()
  virtio-net: introduce a new control to set macaddr

Stefan Hajnoczi (1):
  net: split eth_mac_addr for better error handling

 drivers/net/virtio_net.c        | 110 ++++++++++++++++++++++------------------
 include/linux/etherdevice.h     |   2 +
 include/uapi/linux/virtio_net.h |   8 ++-
 net/ethernet/eth.c              |  43 +++++++++++++---
 4 files changed, 107 insertions(+), 56 deletions(-)

-- 
1.7.11.7

From: Amos Kong <akong at redhat.com>

We want to send vq command to set mac address in
virtnet_set_mac_address(), so do this function moving.
Fixed a little issue of coding style.

Signed-off-by: Amos Kong <akong at redhat.com>
---
 drivers/net/virtio_net.c | 89 ++++++++++++++++++++++++------------------------
 1 file changed, 44 insertions(+), 45 deletions(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index a6fcf15..395ab4f 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -753,6 +753,50 @@ static netdev_tx_t start_xmit(struct sk_buff *skb, struct
net_device *dev)
 	return NETDEV_TX_OK;
 }
 
+/*
+ * Send command via the control virtqueue and check status.  Commands
+ * supported by the hypervisor, as indicated by feature bits, should
+ * never fail unless improperly formated.
+ */
+static bool virtnet_send_command(struct virtnet_info *vi, u8 class, u8 cmd,
+				 struct scatterlist *data, int out, int in)
+{
+	struct scatterlist *s, sg[VIRTNET_SEND_COMMAND_SG_MAX + 2];
+	struct virtio_net_ctrl_hdr ctrl;
+	virtio_net_ctrl_ack status = ~0;
+	unsigned int tmp;
+	int i;
+
+	/* Caller should know better */
+	BUG_ON(!virtio_has_feature(vi->vdev, VIRTIO_NET_F_CTRL_VQ) ||
+		(out + in > VIRTNET_SEND_COMMAND_SG_MAX));
+
+	out++; /* Add header */
+	in++; /* Add return status */
+
+	ctrl.class = class;
+	ctrl.cmd = cmd;
+
+	sg_init_table(sg, out + in);
+
+	sg_set_buf(&sg[0], &ctrl, sizeof(ctrl));
+	for_each_sg(data, s, out + in - 2, i)
+		sg_set_buf(&sg[i + 1], sg_virt(s), s->length);
+	sg_set_buf(&sg[out + in - 1], &status, sizeof(status));
+
+	BUG_ON(virtqueue_add_buf(vi->cvq, sg, out, in, vi, GFP_ATOMIC) < 0);
+
+	virtqueue_kick(vi->cvq);
+
+	/* Spin for a response, the kick causes an ioport write, trapping
+	 * into the hypervisor, so the request should be handled immediately.
+	 */
+	while (!virtqueue_get_buf(vi->cvq, &tmp))
+		cpu_relax();
+
+	return status == VIRTIO_NET_OK;
+}
+
 static int virtnet_set_mac_address(struct net_device *dev, void *p)
 {
 	struct virtnet_info *vi = netdev_priv(dev);
@@ -819,51 +863,6 @@ static void virtnet_netpoll(struct net_device *dev)
 }
 #endif
 
-/*
- * Send command via the control virtqueue and check status.  Commands
- * supported by the hypervisor, as indicated by feature bits, should
- * never fail unless improperly formated.
- */
-static bool virtnet_send_command(struct virtnet_info *vi, u8 class, u8 cmd,
-				 struct scatterlist *data, int out, int in)
-{
-	struct scatterlist *s, sg[VIRTNET_SEND_COMMAND_SG_MAX + 2];
-	struct virtio_net_ctrl_hdr ctrl;
-	virtio_net_ctrl_ack status = ~0;
-	unsigned int tmp;
-	int i;
-
-	/* Caller should know better */
-	BUG_ON(!virtio_has_feature(vi->vdev, VIRTIO_NET_F_CTRL_VQ) ||
-		(out + in > VIRTNET_SEND_COMMAND_SG_MAX));
-
-	out++; /* Add header */
-	in++; /* Add return status */
-
-	ctrl.class = class;
-	ctrl.cmd = cmd;
-
-	sg_init_table(sg, out + in);
-
-	sg_set_buf(&sg[0], &ctrl, sizeof(ctrl));
-	for_each_sg(data, s, out + in - 2, i)
-		sg_set_buf(&sg[i + 1], sg_virt(s), s->length);
-	sg_set_buf(&sg[out + in - 1], &status, sizeof(status));
-
-	BUG_ON(virtqueue_add_buf(vi->cvq, sg, out, in, vi, GFP_ATOMIC) < 0);
-
-	virtqueue_kick(vi->cvq);
-
-	/*
-	 * Spin for a response, the kick causes an ioport write, trapping
-	 * into the hypervisor, so the request should be handled immediately.
-	 */
-	while (!virtqueue_get_buf(vi->cvq, &tmp))
-		cpu_relax();
-
-	return status == VIRTIO_NET_OK;
-}
-
 static void virtnet_ack_link_announce(struct virtnet_info *vi)
 {
 	rtnl_lock();
-- 
1.7.11.7

From: Stefan Hajnoczi <stefanha at gmail.com>

When we set mac address, software mac address in system and hardware mac
address all need to be updated. Current eth_mac_addr() doesn't allow
callers to implement error handling nicely.

This patch split eth_mac_addr() to prepare part and real commit part,
then we can prepare first, and try to change hardware address, then do
the real commit if hardware address is set successfully.

Signed-off-by: Stefan Hajnoczi <stefanha at gmail.com>
Signed-off-by: Amos Kong <akong at redhat.com>
---
 include/linux/etherdevice.h |  2 ++
 net/ethernet/eth.c          | 43 ++++++++++++++++++++++++++++++++++++-------
 2 files changed, 38 insertions(+), 7 deletions(-)

diff --git a/include/linux/etherdevice.h b/include/linux/etherdevice.h
index 243eea1..5cc6e0e 100644
--- a/include/linux/etherdevice.h
+++ b/include/linux/etherdevice.h
@@ -40,6 +40,8 @@ extern int eth_header_cache(const struct neighbour *neigh,
struct hh_cache *hh,
 extern void eth_header_cache_update(struct hh_cache *hh,
 				    const struct net_device *dev,
 				    const unsigned char *haddr);
+extern int eth_prepare_mac_addr_change(struct net_device *dev, void *p);
+extern void eth_commit_mac_addr_change(struct net_device *dev, void *p);
 extern int eth_mac_addr(struct net_device *dev, void *p);
 extern int eth_change_mtu(struct net_device *dev, int new_mtu);
 extern int eth_validate_addr(struct net_device *dev);
diff --git a/net/ethernet/eth.c b/net/ethernet/eth.c
index 4efad53..cce73eb 100644
--- a/net/ethernet/eth.c
+++ b/net/ethernet/eth.c
@@ -272,16 +272,11 @@ void eth_header_cache_update(struct hh_cache *hh,
 EXPORT_SYMBOL(eth_header_cache_update);
 
 /**
- * eth_mac_addr - set new Ethernet hardware address
+ * eth_prepare_mac_addr_change - prepare for mac change
  * @dev: network device
  * @p: socket address
- *
- * Change hardware address of device.
- *
- * This doesn't change hardware matching, so needs to be overridden
- * for most real devices.
  */
-int eth_mac_addr(struct net_device *dev, void *p)
+int eth_prepare_mac_addr_change(struct net_device *dev, void *p)
 {
 	struct sockaddr *addr = p;
 
@@ -289,9 +284,43 @@ int eth_mac_addr(struct net_device *dev, void *p)
 		return -EBUSY;
 	if (!is_valid_ether_addr(addr->sa_data))
 		return -EADDRNOTAVAIL;
+	return 0;
+}
+EXPORT_SYMBOL(eth_prepare_mac_addr_change);
+
+/**
+ * eth_commit_mac_addr_change - commit mac change
+ * @dev: network device
+ * @p: socket address
+ */
+void eth_commit_mac_addr_change(struct net_device *dev, void *p)
+{
+	struct sockaddr *addr = p;
+
 	memcpy(dev->dev_addr, addr->sa_data, ETH_ALEN);
 	/* if device marked as NET_ADDR_RANDOM, reset it */
 	dev->addr_assign_type &= ~NET_ADDR_RANDOM;
+}
+EXPORT_SYMBOL(eth_commit_mac_addr_change);
+
+/**
+ * eth_mac_addr - set new Ethernet hardware address
+ * @dev: network device
+ * @p: socket address
+ *
+ * Change hardware address of device.
+ *
+ * This doesn't change hardware matching, so needs to be overridden
+ * for most real devices.
+ */
+int eth_mac_addr(struct net_device *dev, void *p)
+{
+	int ret;
+
+	ret = eth_prepare_mac_addr_change(dev, p);
+	if (ret < 0)
+		return ret;
+	eth_commit_mac_addr_change(dev, p);
 	return 0;
 }
 EXPORT_SYMBOL(eth_mac_addr);
-- 
1.7.11.7

From: Amos Kong <akong at 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 <akong at redhat.com>
---
 drivers/net/virtio_net.c        | 21 ++++++++++++++++++---
 include/uapi/linux/virtio_net.h |  8 +++++++-
 2 files changed, 25 insertions(+), 4 deletions(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 395ab4f..701408a 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -802,14 +802,28 @@ 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 sockaddr *addr = p;
+	struct scatterlist sg;
 
-	ret = eth_mac_addr(dev, p);
+	ret = eth_prepare_mac_addr_change(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, addr->sa_data, 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");
+			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);
+				  addr->sa_data, dev->addr_len);
+	}
+
+	eth_commit_mac_addr_change(dev, p);
 
 	return 0;
 }
@@ -1627,6 +1641,7 @@ 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