Virtualization - Jan 2013 - [RFC PATCH 0/2] 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. 

Second patch introduced a new vq control command to set mac
address in one time.

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

 drivers/net/virtio_net.c        | 105 ++++++++++++++++++++++------------------
 include/uapi/linux/virtio_net.h |   8 ++-
 2 files changed, 66 insertions(+), 47 deletions(-)

-- 
1.7.11.7

From: Amos Kong <akong at redhat.com>

We will send vq command to set mac address in virtnet_set_mac_address()
a little fix 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: 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
in one time.

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        | 16 +++++++++++++++-
 include/uapi/linux/virtio_net.h |  8 +++++++-
 2 files changed, 22 insertions(+), 2 deletions(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 395ab4f..ff22bcd 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -803,13 +803,26 @@ static int virtnet_set_mac_address(struct net_device *dev,
void *p)
 	struct virtio_device *vdev = vi->vdev;
 	int ret;
 
+	struct scatterlist sg;
+
 	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)) {
+		/* Set MAC address by sending vq command */
+		sg_init_one(&sg, dev->dev_addr, dev->addr_len);
+		virtnet_send_command(vi, VIRTIO_NET_CTRL_MAC,
+				     VIRTIO_NET_CTRL_MAC_ADDR_SET,
+				     &sg, 1, 0);
+		return 0;
+	}
+
+	if (virtio_has_feature(vdev, VIRTIO_NET_F_MAC)) {
+		/* Set MAC address by writing config space */
 		vdev->config->set(vdev, offsetof(struct virtio_net_config, mac),
 		                  dev->dev_addr, dev->addr_len);
+	}
 
 	return 0;
 }
@@ -1627,6 +1640,7 @@ 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

On 01/10/2013 10:45 PM, akong at redhat.com wrote:
> From: Amos Kong <akong at redhat.com>
>
> We will send vq command to set mac address in virtnet_set_mac_address()
> a little fix of coding style
Maybe what you need is just a forward declaration.
>
> 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();

From: Amos Kong <akong at redhat.com>

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 in one time.

VIRTIO_NET_F_CTRL_MAC_ADDR is a new feature bit for compatibility.

Signed-off-by: Amos Kong <akong at redhat.com>
---
 hw/virtio-net.c | 9 +++++++++
 hw/virtio-net.h | 9 ++++++++-
 2 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/hw/virtio-net.c b/hw/virtio-net.c
index dc7c6d6..fc11106 100644
--- a/hw/virtio-net.c
+++ b/hw/virtio-net.c
@@ -247,6 +247,7 @@ static uint32_t virtio_net_get_features(VirtIODevice *vdev,
uint32_t features)
     VirtIONet *n = to_virtio_net(vdev);
 
     features |= (1 << VIRTIO_NET_F_MAC);
+    features |= (1 << VIRTIO_NET_F_CTRL_MAC_ADDR);
 
     if (!peer_has_vnet_hdr(n)) {
         features &= ~(0x1 << VIRTIO_NET_F_CSUM);
@@ -282,6 +283,7 @@ static uint32_t virtio_net_bad_features(VirtIODevice *vdev)
     /* Linux kernel 2.6.25.  It understood MAC (as everyone must),
      * but also these: */
     features |= (1 << VIRTIO_NET_F_MAC);
+    features |= (1 << VIRTIO_NET_F_CTRL_MAC_ADDR);
     features |= (1 << VIRTIO_NET_F_CSUM);
     features |= (1 << VIRTIO_NET_F_HOST_TSO4);
     features |= (1 << VIRTIO_NET_F_HOST_TSO6);
@@ -349,6 +351,13 @@ static int virtio_net_handle_mac(VirtIONet *n, uint8_t cmd,
 {
     struct virtio_net_ctrl_mac mac_data;
 
+    if (cmd == VIRTIO_NET_CTRL_MAC_ADDR_SET && elem->out_num == 2) {
+        /* Set MAC address */
+        memcpy(n->mac, elem->out_sg[1].iov_base,
elem->out_sg[1].iov_len);
+        qemu_format_nic_info_str(&n->nic->nc, n->mac);
+        return VIRTIO_NET_OK;
+    }
+
     if (cmd != VIRTIO_NET_CTRL_MAC_TABLE_SET || elem->out_num != 3 ||
         elem->out_sg[1].iov_len < sizeof(mac_data) ||
         elem->out_sg[2].iov_len < sizeof(mac_data))
diff --git a/hw/virtio-net.h b/hw/virtio-net.h
index d46fb98..9394cc0 100644
--- a/hw/virtio-net.h
+++ b/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
-- 
1.7.11.7

On 01/10/2013 10:45 PM, akong at redhat.com wrote:
> 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
> in one time.
>
> 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        | 16 +++++++++++++++-
>  include/uapi/linux/virtio_net.h |  8 +++++++-
>  2 files changed, 22 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 395ab4f..ff22bcd 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -803,13 +803,26 @@ static int virtnet_set_mac_address(struct net_device
*dev, void *p)
>  	struct virtio_device *vdev = vi->vdev;
>  	int ret;
>  
> +	struct scatterlist sg;
> +
>  	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)) {
> +		/* Set MAC address by sending vq command */
> +		sg_init_one(&sg, dev->dev_addr, dev->addr_len);
> +		virtnet_send_command(vi, VIRTIO_NET_CTRL_MAC,
> +				     VIRTIO_NET_CTRL_MAC_ADDR_SET,
> +				     &sg, 1, 0);
> +		return 0;
> +	}
> +
Better to check the return of virtnet_send_command() and give a warn
like other command. Btw, need we fail back to try the old way
then?
> +	if (virtio_has_feature(vdev, VIRTIO_NET_F_MAC)) {
> +		/* Set MAC address by writing config space */
>  		vdev->config->set(vdev, offsetof(struct virtio_net_config, mac),
>  		                  dev->dev_addr, dev->addr_len);
> +	}
>  
>  	return 0;
>  }
> @@ -1627,6 +1640,7 @@ 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

On Thu, Jan 10, 2013 at 10:51:52PM +0800, Jason Wang
wrote:
> On 01/10/2013 10:45 PM, akong at redhat.com wrote:
> > From: Amos Kong <akong at redhat.com>
> >
> > We will send vq command to set mac address in
virtnet_set_mac_address()
> > a little fix of coding style
> 
> Maybe what you need is just a forward declaration.

Nah functions should be ordered sensibly.
> >
> > Signed-off-by: Amos Kong <akong at redhat.com>

On Thu, Jan 10, 2013 at 10:45:39PM +0800, akong at redhat.com
wrote:
> 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. 
> 
> Second patch introduced a new vq control command to set mac
> address in one time.
I just posted RFC patches (kernel & qemu) out,
specifiction update will be sent when the solution
is accepted.

MST has another solution:
1. add a feature to disable mac address in pci space
2. introduce a new vq control cmd to add new mac address
   to mac filter table. (no long check n->mac in receiver_filter())

Welcome to give comments, thanks!
Amos

On Thu, Jan 10, 2013 at 10:45:39PM +0800, akong at redhat.com
wrote:
> 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. 
> 
> Second patch introduced a new vq control command to set mac
> address in one time.
As you mention we could alternatively do it without
new commands, simply add a feature bit that says that MACs are
in the mac table.
This would be a much bigger patch, and I'm fine with either way.
Rusty what do you think?
> Amos Kong (2):
>   move virtnet_send_command() above virtnet_set_mac_address()
>   virtio-net: introduce a new control to set macaddr
> 
>  drivers/net/virtio_net.c        | 105
++++++++++++++++++++++------------------
>  include/uapi/linux/virtio_net.h |   8 ++-
>  2 files changed, 66 insertions(+), 47 deletions(-)
> 
> -- 
> 1.7.11.7