Re: [V6 PATCH] virtio-net: send gratuitous packets when needed
From: Jason Wang
Date: Thu Apr 05 2012 - 01:56:37 EST
On 04/04/2012 03:49 PM, Michael S. Tsirkin wrote:
On Wed, Mar 28, 2012 at 01:44:28PM +0800, Jason Wang wrote:
As hypervior does not have the knowledge of guest network configuration, it's
better to ask guest to send gratuitous packets when needed.
Guest tests VIRTIO_NET_S_ANNOUNCE bit during config change interrupt and when it
is set, a workqueue is scheduled to send gratuitous packet through
NETDEV_NOTIFY_PEERS. This feature is negotiated through bit
VIRTIO_NET_F_GUEST_ANNOUNCE.
Changes from v5:
- notify the chain before acking the link annoucement
- ack the link announcement notification through control vq
Changes from v4:
- typos
- handle workqueue unconditionally
- move VIRTIO_NET_S_ANNOUNCE to bit 8 to separate rw bits from ro bits
Changes from v3:
- cancel the workqueue during freeze
Changes from v2:
- fix the race between unregister_dev() and workqueue
Signed-off-by: Jason Wang<jasowang@xxxxxxxxxx>
I think this needs some fixes. See below.
Thanks.
---
drivers/net/virtio_net.c | 32 +++++++++++++++++++++++++++++++-
include/linux/virtio_net.h | 13 +++++++++++++
2 files changed, 44 insertions(+), 1 deletions(-)
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 4880aa8..0f60da7 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -72,6 +72,9 @@ struct virtnet_info {
/* Work struct for refilling if we run low on memory. */
struct delayed_work refill;
+ /* Work struct for sending gratuitous packets. */
A bit confusing: it does not send anything itself.
A better comment 'for announcing the existence of device
on the network'.
+ struct work_struct announce;
+
/* Chain pages by the private ptr. */
struct page *pages;
@@ -781,12 +784,30 @@ static bool virtnet_send_command(struct virtnet_info *vi, u8 class, u8 cmd,
return status == VIRTIO_NET_OK;
}
+static void virtnet_ack_link_announce(struct virtnet_info *vi)
+{
+ if (!virtnet_send_command(vi, VIRTIO_NET_CTRL_ANNOUNCE,
+ VIRTIO_NET_CTRL_ANNOUNCE_ACK, NULL,
+ 0, 0)) {
This can run in parallel with other commands. That's pretty bad -
will corrupt the cvq.
Take rtnl lock around calls to this function?
It's only used by callbacks of netif_notify_peers(), so rtnl lock have
already been hold. Add a comment to clarify this?
+ dev_warn(&vi->dev->dev, "Failed to ack link nnounce.\n");
announce
Sorry for the typos, would double check in the future.
+ }
Better to drop {} around a single statement.
+}
+
+static void announce_work(struct work_struct *work)
+{
+ struct virtnet_info *vi = container_of(work, struct virtnet_info,
+ announce);
+ netif_notify_peers(vi->dev);
+ virtnet_ack_link_announce(vi);
+}
+
static int virtnet_close(struct net_device *dev)
{
struct virtnet_info *vi = netdev_priv(dev);
/* Make sure refill_work doesn't re-enable napi! */
cancel_delayed_work_sync(&vi->refill);
+ cancel_work_sync(&vi->announce);
I think that a config change event can trigger after this point,
so cancel here won't be effective. But why do it here?
virtnet_remove not a better place? We can do it
after remove_vq_common.
Sure.
napi_disable(&vi->napi);
return 0;
@@ -962,11 +983,17 @@ static void virtnet_update_status(struct virtnet_info *vi)
return;
/* Ignore unknown (future) status bits */
- v&= VIRTIO_NET_S_LINK_UP;
+ v&= VIRTIO_NET_S_LINK_UP | VIRTIO_NET_S_ANNOUNCE;
The announce bit in vi->status is always clear,
so this is IMO confusing. I would do:
if (v& VIRTIO_NET_S_ANNOUNCE) {
schedule
}
v&= VIRTIO_NET_S_LINK_UP;
and the rest of the logic is not necessary then.
Also, this might run extra ack announce commands after
VIRTIO_NET_S_ANNOUNCE bit is clear. The spec
isn't clear on whether this is legal.
It would be very hard to fix this, so let's add a comment
stating that it's legal, and clarify the spec
in any case.
How about delay the clearing of VIRTIO_NET_S_ANNOUNCE bit in the
workqueue and protect the updating with
spinlock_irqsave()/spinloc_irqrestore()? Then later notification would
be suppressed if the sending is not completed.
if (vi->status == v)
return;
+ if (v& VIRTIO_NET_S_ANNOUNCE) {
+ v&= ~VIRTIO_NET_S_ANNOUNCE;
+ if (v& VIRTIO_NET_S_LINK_UP)
+ schedule_work(&vi->announce);
I think we really want an nrt wq here - if this triggers
multiple times there's no good reason to try and run
the ack command many times in parallel.
Yes.
+ }
+
vi->status = v;
if (vi->status& VIRTIO_NET_S_LINK_UP) {
@@ -1076,6 +1103,7 @@ static int virtnet_probe(struct virtio_device *vdev)
goto free;
INIT_DELAYED_WORK(&vi->refill, refill_work);
+ INIT_WORK(&vi->announce, announce_work);
sg_init_table(vi->rx_sg, ARRAY_SIZE(vi->rx_sg));
sg_init_table(vi->tx_sg, ARRAY_SIZE(vi->tx_sg));
@@ -1187,6 +1215,7 @@ static int virtnet_freeze(struct virtio_device *vdev)
virtqueue_disable_cb(vi->svq);
if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_CTRL_VQ))
virtqueue_disable_cb(vi->cvq);
+ cancel_work_sync(&vi->announce);
A config change event can trigger after this point,
so cancel here won't be effective.
Possibly, we need state like config_enable in the block
device.
Probably needed.
Also, what exactly will happen on suspend?
As we reset, ANNOUCE bit will be clear so -
do we forget to announce? Probably not good ...
This problem should be the same as normal suspending/resuming, if user
want to announce the link they should use arp_notify instead.
netif_device_detach(vi->dev);
cancel_delayed_work_sync(&vi->refill);
@@ -1233,6 +1262,7 @@ static unsigned int features[] = {
VIRTIO_NET_F_GUEST_ECN, VIRTIO_NET_F_GUEST_UFO,
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,
};
static struct virtio_driver virtio_net_driver = {
diff --git a/include/linux/virtio_net.h b/include/linux/virtio_net.h
index 970d5a2..383e8a0 100644
--- a/include/linux/virtio_net.h
+++ b/include/linux/virtio_net.h
@@ -49,8 +49,10 @@
#define VIRTIO_NET_F_CTRL_RX 18 /* Control channel RX mode support */
#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_GUEST_ANNOUNCE 21 /* Guest can send gratituous packet */
Rusty aligned the comments using tabs so let's do it here too?
A better comment 'can announce device on the network'.
#define VIRTIO_NET_S_LINK_UP 1 /* Link is up */
+#define VIRTIO_NET_S_ANNOUNCE 2 /* Announcement is needed */
why 3 spaces before the value here?
struct virtio_net_config {
/* The config defining mac address (if VIRTIO_NET_F_MAC) */
@@ -152,4 +154,15 @@ struct virtio_net_ctrl_mac {
#define VIRTIO_NET_CTRL_VLAN_ADD 0
#define VIRTIO_NET_CTRL_VLAN_DEL 1
+/*
+ * Control link announce acknowledgement
+ *
+ * The command VIRTIO_NET_CTRL_ANNOUNCE_ACK is used to indicate that
+ * driver has recevied the notification and device would clear the
s/recevied/received/
A bit clearer to replace 'and' with ; here.
+ * VIRTIO_NET_S_ANNOUNCE bit in the status filed after it received
s/filed/field/
s/received/receives/
+ * this command.
+ */
+#define VIRTIO_NET_CTRL_ANNOUNCE 3
+ #define VIRTIO_NET_CTRL_ANNOUNCE_ACK 0
+
#endif /* _LINUX_VIRTIO_NET_H */
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