[PATCH net] net: mscc: ocelot: install MAC addresses in .ndo_set_rx_mode from process context

[PATCH net] net: mscc: ocelot: install MAC addresses in .ndo_set_rx_mode from process context

[Vladimir Oltean]

Currently ocelot_set_rx_mode calls ocelot_mact_learn directly, which has
a very nice ocelot_mact_wait_for_completion at the end. Introduced in
commit 639c1b2625af ("net: mscc: ocelot: Register poll timeout should be
wall time not attempts"), this function uses readx_poll_timeout which
triggers a lot of lockdep warnings and is also dangerous to use from
atomic context, leading to lockups and panics.

Steen Hegelund added a poll timeout of 100 ms for checking the MAC
table, a duration which is clearly absurd to poll in atomic context.
So we need to defer the MAC table access to process context, which we do
via a dynamically allocated workqueue which contains all there is to
know about the MAC table operation it has to do.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
---
 drivers/net/ethernet/mscc/ocelot_net.c | 81 +++++++++++++++++++++++++-
 1 file changed, 78 insertions(+), 3 deletions(-)

diff --git a/drivers/net/ethernet/mscc/ocelot_net.c b/drivers/net/ethernet/mscc/ocelot_net.c
index c65ae6f75a16..2f536692d61e 100644
--- a/drivers/net/ethernet/mscc/ocelot_net.c
+++ b/drivers/net/ethernet/mscc/ocelot_net.c
@@ -414,13 +414,82 @@ static int ocelot_port_xmit(struct sk_buff *skb, struct net_device *dev)
 	return NETDEV_TX_OK;
 }
 
+enum ocelot_action_type {
+	OCELOT_MACT_LEARN,
+	OCELOT_MACT_FORGET,
+};
+
+struct ocelot_mact_work_ctx {
+	struct work_struct work;
+	struct ocelot *ocelot;
+	enum ocelot_action_type type;
+	union {
+		/* OCELOT_MACT_LEARN */
+		struct {
+			int pgid;
+			enum macaccess_entry_type entry_type;
+			unsigned char addr[ETH_ALEN];
+			u16 vid;
+		} learn;
+		/* OCELOT_MACT_FORGET */
+		struct {
+			unsigned char addr[ETH_ALEN];
+			u16 vid;
+		} forget;
+	};
+};
+
+#define ocelot_work_to_ctx(x) \
+	container_of((x), struct ocelot_mact_work_ctx, work)
+
+static void ocelot_mact_work(struct work_struct *work)
+{
+	struct ocelot_mact_work_ctx *w = ocelot_work_to_ctx(work);
+	struct ocelot *ocelot = w->ocelot;
+
+	switch (w->type) {
+	case OCELOT_MACT_LEARN:
+		ocelot_mact_learn(ocelot, w->learn.pgid, w->learn.addr,
+				  w->learn.vid, w->learn.entry_type);
+		break;
+	case OCELOT_MACT_FORGET:
+		ocelot_mact_forget(ocelot, w->forget.addr, w->forget.vid);
+		break;
+	default:
+		break;
+	};
+
+	kfree(w);
+}
+
+static int ocelot_enqueue_mact_action(struct ocelot *ocelot,
+				      const struct ocelot_mact_work_ctx *ctx)
+{
+	struct ocelot_mact_work_ctx *w = kmalloc(sizeof(*w), GFP_ATOMIC);
+
+	if (!w)
+		return -ENOMEM;
+
+	memcpy(w, ctx, sizeof(*w));
+	w->ocelot = ocelot;
+	INIT_WORK(&w->work, ocelot_mact_work);
+	schedule_work(&w->work);
+
+	return 0;
+}
+
 static int ocelot_mc_unsync(struct net_device *dev, const unsigned char *addr)
 {
 	struct ocelot_port_private *priv = netdev_priv(dev);
 	struct ocelot_port *ocelot_port = &priv->port;
 	struct ocelot *ocelot = ocelot_port->ocelot;
+	struct ocelot_mact_work_ctx w;
+
+	ether_addr_copy(w.forget.addr, addr);
+	w.forget.vid = ocelot_port->pvid_vlan.vid;
+	w.type = OCELOT_MACT_FORGET;
 
-	return ocelot_mact_forget(ocelot, addr, ocelot_port->pvid_vlan.vid);
+	return ocelot_enqueue_mact_action(ocelot, &w);
 }
 
 static int ocelot_mc_sync(struct net_device *dev, const unsigned char *addr)
@@ -428,9 +497,15 @@ static int ocelot_mc_sync(struct net_device *dev, const unsigned char *addr)
 	struct ocelot_port_private *priv = netdev_priv(dev);
 	struct ocelot_port *ocelot_port = &priv->port;
 	struct ocelot *ocelot = ocelot_port->ocelot;
+	struct ocelot_mact_work_ctx w;
+
+	ether_addr_copy(w.learn.addr, addr);
+	w.learn.vid = ocelot_port->pvid_vlan.vid;
+	w.learn.pgid = PGID_CPU;
+	w.learn.entry_type = ENTRYTYPE_LOCKED;
+	w.type = OCELOT_MACT_LEARN;
 
-	return ocelot_mact_learn(ocelot, PGID_CPU, addr,
-				 ocelot_port->pvid_vlan.vid, ENTRYTYPE_LOCKED);
+	return ocelot_enqueue_mact_action(ocelot, &w);
 }
 
 static void ocelot_set_rx_mode(struct net_device *dev)
-- 
2.25.1

Re: [PATCH net] net: mscc: ocelot: install MAC addresses in .ndo_set_rx_mode from process context

[Florian Fainelli]

On 12/4/2020 9:09 AM, Vladimir Oltean wrote:
> Currently ocelot_set_rx_mode calls ocelot_mact_learn directly, which has
> a very nice ocelot_mact_wait_for_completion at the end. Introduced in
> commit 639c1b2625af ("net: mscc: ocelot: Register poll timeout should be
> wall time not attempts"), this function uses readx_poll_timeout which
> triggers a lot of lockdep warnings and is also dangerous to use from
> atomic context, leading to lockups and panics.
> 
> Steen Hegelund added a poll timeout of 100 ms for checking the MAC
> table, a duration which is clearly absurd to poll in atomic context.
> So we need to defer the MAC table access to process context, which we do
> via a dynamically allocated workqueue which contains all there is to
> know about the MAC table operation it has to do.
> 
> Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>

Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>

Did you want to have a Fixes tag to help identify how far back this
needs to be back ported?
-- 
Florian

Re: [PATCH net] net: mscc: ocelot: install MAC addresses in .ndo_set_rx_mode from process context

[Vladimir Oltean]

On Fri, Dec 04, 2020 at 09:34:54AM -0800, Florian Fainelli wrote:
> On 12/4/2020 9:09 AM, Vladimir Oltean wrote:
> > Currently ocelot_set_rx_mode calls ocelot_mact_learn directly, which has
> > a very nice ocelot_mact_wait_for_completion at the end. Introduced in
> > commit 639c1b2625af ("net: mscc: ocelot: Register poll timeout should be
> > wall time not attempts"), this function uses readx_poll_timeout which
> > triggers a lot of lockdep warnings and is also dangerous to use from
> > atomic context, leading to lockups and panics.
> > 
> > Steen Hegelund added a poll timeout of 100 ms for checking the MAC
> > table, a duration which is clearly absurd to poll in atomic context.
> > So we need to defer the MAC table access to process context, which we do
> > via a dynamically allocated workqueue which contains all there is to
> > know about the MAC table operation it has to do.
> > 
> > Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
> 
> Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
> 
> Did you want to have a Fixes tag to help identify how far back this
> needs to be back ported?

I was on the fence about whether I should even target "net", considering
that it's not a small patch. But the lockdep warnings are super annoying,
I cannot do anything further on the ocelot switchdev driver with them.

There's also a small concern I have that I should have taken a reference
count on ocelot->dev using get_device, to avoid racing with the unbind.
I think I'll send a v2 with this and a Fixes: tag.