[PATCH net] hv_netvsc: Fix race between VF offering and VF association message from host

[Gaurav Kohli <gauravkohli@linux.microsoft.com>]

During vm boot, there might be possibility that vf registration
call comes before the vf association from host to vm.

And this might break netvsc vf path, To prevent the same block
vf registration until vf bind message comes from host.

Cc: stable@vger.kernel.org
Fixes: 00d7ddba11436 ("hv_netvsc: pair VF based on serial number")
Signed-off-by: Gaurav Kohli <gauravkohli@linux.microsoft.com>
---
 drivers/net/hyperv/hyperv_net.h |  3 ++-
 drivers/net/hyperv/netvsc.c     |  5 +++++
 drivers/net/hyperv/netvsc_drv.c | 18 ++++++++++++++++++
 3 files changed, 25 insertions(+), 1 deletion(-)

diff --git a/drivers/net/hyperv/hyperv_net.h b/drivers/net/hyperv/hyperv_net.h
index 25b38a374e3c..dd5919ec408b 100644
--- a/drivers/net/hyperv/hyperv_net.h
+++ b/drivers/net/hyperv/hyperv_net.h
@@ -1051,7 +1051,8 @@ struct net_device_context {
 	u32 vf_alloc;
 	/* Serial number of the VF to team with */
 	u32 vf_serial;
-
+	/* completion variable to confirm vf association */
+	struct completion vf_add;
 	/* Is the current data path through the VF NIC? */
 	bool  data_path_is_vf;
 
diff --git a/drivers/net/hyperv/netvsc.c b/drivers/net/hyperv/netvsc.c
index 8bcba6f21aa9..6531d8d9f17f 100644
--- a/drivers/net/hyperv/netvsc.c
+++ b/drivers/net/hyperv/netvsc.c
@@ -1582,6 +1582,11 @@ static void netvsc_send_vf(struct net_device *ndev,
 
 	net_device_ctx->vf_alloc = nvmsg->msg.v4_msg.vf_assoc.allocated;
 	net_device_ctx->vf_serial = nvmsg->msg.v4_msg.vf_assoc.serial;
+
+	if (net_device_ctx->vf_alloc)
+		complete(&net_device_ctx->vf_add);
+	else
+		reinit_completion(&net_device_ctx->vf_add);
 	netdev_info(ndev, "VF slot %u %s\n",
 		    net_device_ctx->vf_serial,
 		    net_device_ctx->vf_alloc ? "added" : "removed");
diff --git a/drivers/net/hyperv/netvsc_drv.c b/drivers/net/hyperv/netvsc_drv.c
index c27cb1267ca5..393c69430147 100644
--- a/drivers/net/hyperv/netvsc_drv.c
+++ b/drivers/net/hyperv/netvsc_drv.c
@@ -2309,6 +2309,18 @@ static struct net_device *get_netvsc_byslot(const struct net_device *vf_netdev)
 
 	}
 
+	/* Fallback path to check synthetic vf with
+	 * help of mac addr
+	 */
+	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");
+			return ndev;
+		}
+	}
+
 	netdev_notice(vf_netdev,
 		      "no netdev found for vf serial:%u\n", serial);
 	return NULL;
@@ -2405,6 +2417,11 @@ static int netvsc_vf_changed(struct net_device *vf_netdev, unsigned long event)
 	if (net_device_ctx->data_path_is_vf == vf_is_up)
 		return NOTIFY_OK;
 
+	if (vf_is_up && !net_device_ctx->vf_alloc) {
+		netdev_info(ndev, "Waiting for the VF association from host\n");
+		wait_for_completion(&net_device_ctx->vf_add);
+	}
+
 	ret = netvsc_switch_datapath(ndev, vf_is_up);
 
 	if (ret) {
@@ -2475,6 +2492,7 @@ static int netvsc_probe(struct hv_device *dev,
 
 	INIT_DELAYED_WORK(&net_device_ctx->dwork, netvsc_link_change);
 
+	init_completion(&net_device_ctx->vf_add);
 	spin_lock_init(&net_device_ctx->lock);
 	INIT_LIST_HEAD(&net_device_ctx->reconfig_events);
 	INIT_DELAYED_WORK(&net_device_ctx->vf_takeover, netvsc_vf_setup);
-- 
2.17.1