[PATCH net,v4, 3/3] hv_netvsc: Mark VF as slave before exposing it to user-mode

From: Haiyang Zhang
Date: Fri Nov 10 2023 - 12:57:44 EST


From: Long Li <longli@xxxxxxxxxxxxx>

When a VF is being exposed form the kernel, it should be marked as "slave"
before exposing to the user-mode. The VF is not usable without netvsc
running as master. The user-mode should never see a VF without the "slave"
flag.

This commit moves the code of setting the slave flag to the time before
VF is exposed to user-mode.

Cc: stable@xxxxxxxxxxxxxxx
Fixes: 0c195567a8f6 ("netvsc: transparent VF management")
Signed-off-by: Long Li <longli@xxxxxxxxxxxxx>
Signed-off-by: Haiyang Zhang <haiyangz@xxxxxxxxxxxxx>

---
v4:
Add comments in get_netvsc_byslot() explaining the need to check dev_addr
v2:
Use a new function to handle NETDEV_POST_INIT.
---
drivers/net/hyperv/netvsc_drv.c | 32 +++++++++++++++++++++++---------
1 file changed, 23 insertions(+), 9 deletions(-)

diff --git a/drivers/net/hyperv/netvsc_drv.c b/drivers/net/hyperv/netvsc_drv.c
index 1d1491da303b..52dbf1de7347 100644
--- a/drivers/net/hyperv/netvsc_drv.c
+++ b/drivers/net/hyperv/netvsc_drv.c
@@ -2206,9 +2206,6 @@ static int netvsc_vf_join(struct net_device *vf_netdev,
goto upper_link_failed;
}

- /* set slave flag before open to prevent IPv6 addrconf */
- vf_netdev->flags |= IFF_SLAVE;
-
schedule_delayed_work(&ndev_ctx->vf_takeover, VF_TAKEOVER_INT);

call_netdevice_notifiers(NETDEV_JOIN, vf_netdev);
@@ -2315,16 +2312,18 @@ static struct net_device *get_netvsc_byslot(const struct net_device *vf_netdev)

}

- /* Fallback path to check synthetic vf with
- * help of mac addr
+ /* Fallback path to check synthetic vf with help of mac addr.
+ * Because this function can be called before vf_netdev is
+ * initialized (NETDEV_POST_INIT) when its perm_addr has not been copied
+ * from dev_addr, also try to match to its dev_addr.
+ * Note: On Hyper-V and Azure, it's not possible to set a MAC address
+ * on a VF that matches to the MAC of a unrelated NETVSC device.
*/
list_for_each_entry(ndev_ctx, &netvsc_dev_list, list) {
ndev = hv_get_drvdata(ndev_ctx->device_ctx);
- if (ether_addr_equal(vf_netdev->perm_addr, ndev->perm_addr)) {
- netdev_notice(vf_netdev,
- "falling back to mac addr based matching\n");
+ if (ether_addr_equal(vf_netdev->perm_addr, ndev->perm_addr) ||
+ ether_addr_equal(vf_netdev->dev_addr, ndev->perm_addr))
return ndev;
- }
}

netdev_notice(vf_netdev,
@@ -2332,6 +2331,19 @@ static struct net_device *get_netvsc_byslot(const struct net_device *vf_netdev)
return NULL;
}

+static int netvsc_prepare_slave(struct net_device *vf_netdev)
+{
+ struct net_device *ndev;
+
+ ndev = get_netvsc_byslot(vf_netdev);
+ if (!ndev)
+ return NOTIFY_DONE;
+
+ /* set slave flag before open to prevent IPv6 addrconf */
+ vf_netdev->flags |= IFF_SLAVE;
+ return NOTIFY_DONE;
+}
+
static int netvsc_register_vf(struct net_device *vf_netdev)
{
struct net_device_context *net_device_ctx;
@@ -2758,6 +2770,8 @@ static int netvsc_netdev_event(struct notifier_block *this,
return NOTIFY_DONE;

switch (event) {
+ case NETDEV_POST_INIT:
+ return netvsc_prepare_slave(event_dev);
case NETDEV_REGISTER:
return netvsc_register_vf(event_dev);
case NETDEV_UNREGISTER:
--
2.25.1