Re: [PATCH net-next v11 6/9] net: dsa: lan9645x: add vlan support

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---
--- Patch [6]: [PATCH net-next v11 6/9] net: dsa: lan9645x: add vlan support ---
commit 48ea20348797be1134c296e1f56d305fbc50bbe3
Author: Jens Emil Schulz Østergaard <[email protected]>

net: dsa: lan9645x: add vlan support

This adds a new lan9645x_vlan.c implementing port_vlan_filtering,
port_vlan_add and port_vlan_del, backed by a software shadow of the
hardware VLAN table in lan9645x->vlans[]. VID 4095 is reserved as the
port VLAN of standalone ports and VID 0 is used for VLAN-unaware bridge
ports.

> diff --git a/drivers/net/dsa/microchip/lan9645x/lan9645x_main.c b/drivers/net/dsa/microchip/lan9645x/lan9645x_main.c
> index c145d28ffbb99..3281726284dc2 100644
> --- a/drivers/net/dsa/microchip/lan9645x/lan9645x_main.c
> +++ b/drivers/net/dsa/microchip/lan9645x/lan9645x_main.c

[ ... ]

> @@ -521,6 +524,7 @@ static int lan9645x_port_bridge_join(struct dsa_switch *ds, int port,
>  
>  	lan9645x->bridge_mask |= BIT(p->chip_port);
>  	__lan9645x_port_set_host_flood(lan9645x);
> +	lan9645x_vlan_clear_hostmode(p);
>  
>  	mutex_unlock(&lan9645x->fwd_domain_lock);
>  

[ ... ]

> @@ -576,11 +580,52 @@ static void lan9645x_port_bridge_leave(struct dsa_switch *ds, int port,
> +static int lan9645x_port_vlan_add(struct dsa_switch *ds, int port,
> +				  const struct switchdev_obj_port_vlan *vlan,
> +				  struct netlink_ext_ack *extack)
> +{
> +	struct lan9645x *lan9645x = ds->priv;
> +	struct lan9645x_port *p;
> +	bool pvid, untagged;
> +
> +	p = lan9645x_to_port(lan9645x, port);
> +	pvid = !!(vlan->flags & BRIDGE_VLAN_INFO_PVID);
> +	untagged = !!(vlan->flags & BRIDGE_VLAN_INFO_UNTAGGED);
> +
> +	return lan9645x_vlan_port_add_vlan(p, vlan->vid, pvid, untagged,
> +					   extack);
> +}

[ ... ]

> diff --git a/drivers/net/dsa/microchip/lan9645x/lan9645x_main.h b/drivers/net/dsa/microchip/lan9645x/lan9645x_main.h
> index a0cd1707e1149..248c4ab59f1a8 100644
> --- a/drivers/net/dsa/microchip/lan9645x/lan9645x_main.h
> +++ b/drivers/net/dsa/microchip/lan9645x/lan9645x_main.h

[ ... ]

> @@ -156,6 +157,17 @@ enum lan9645x_vlan_port_tag {
>  	LAN9645X_TAG_ALL = 3,
>  };
>  
> +struct lan9645x_vlan {
> +	u32 portmask: 10, /* ports 0-8 + CPU port module */
> +	    untagged: 9, /* ports 0-8 */
> +	    src_chk: 1,
> +	    mir: 1,
> +	    lrn_dis: 1,
> +	    prv_vlan: 1,
> +	    fld_dis: 1,
> +	    s_fwd_ena: 1;
> +};
> +

[ ... ]

> @@ -180,6 +192,9 @@ struct lan9645x {
>  	u16 bridge_fwd_mask; /* Mask for forwarding bridged ports */
>  	struct mutex fwd_domain_lock; /* lock forwarding configuration */
>  
> +	/* VLAN entries */
> +	struct lan9645x_vlan vlans[VLAN_N_VID];
> +
>  	int num_port_dis;
>  };

[ ... ]

> diff --git a/drivers/net/dsa/microchip/lan9645x/lan9645x_port.c b/drivers/net/dsa/microchip/lan9645x/lan9645x_port.c
> index 0642b59419c25..0548904dc4bd2 100644
> --- a/drivers/net/dsa/microchip/lan9645x/lan9645x_port.c
> +++ b/drivers/net/dsa/microchip/lan9645x/lan9645x_port.c
> @@ -210,5 +210,8 @@ int lan9645x_port_setup(struct dsa_switch *ds, int port)
>  		ANA_PORT_CFG_PORTID_VAL,
>  		lan9645x, ANA_PORT_CFG(p->chip_port));
>  
> +	if (p->chip_port != lan9645x->npi)
> +		lan9645x_vlan_set_hostmode(p);
> +
>  	return 0;
>  }

> diff --git a/drivers/net/dsa/microchip/lan9645x/lan9645x_vlan.c b/drivers/net/dsa/microchip/lan9645x/lan9645x_vlan.c
> new file mode 100644
> index 0000000000000..e2116132b4d48
> --- /dev/null
> +++ b/drivers/net/dsa/microchip/lan9645x/lan9645x_vlan.c

[ ... ]

> +static int lan9645x_vlan_hw_wr(struct lan9645x *lan9645x, u16 vid)
> +{
> +	struct lan9645x_vlan *v = &lan9645x->vlans[vid];
> +	bool cpu_dis = !(v->portmask & BIT(lan9645x->num_phys_ports));
> +	u32 val;
> +	int err;
> +
> +	val = ANA_VLANTIDX_VLAN_PGID_CPU_DIS_SET(cpu_dis) |
> +	      ANA_VLANTIDX_V_INDEX_SET(vid) |
> +	      ANA_VLANTIDX_VLAN_SEC_FWD_ENA_SET(v->s_fwd_ena) |
> +	      ANA_VLANTIDX_VLAN_FLOOD_DIS_SET(v->fld_dis) |
> +	      ANA_VLANTIDX_VLAN_PRIV_VLAN_SET(v->prv_vlan) |
> +	      ANA_VLANTIDX_VLAN_LEARN_DISABLED_SET(v->lrn_dis) |
> +	      ANA_VLANTIDX_VLAN_MIRROR_SET(v->mir) |
> +	      ANA_VLANTIDX_VLAN_SRC_CHK_SET(v->src_chk);
> +
> +	lan_wr(val, lan9645x, ANA_VLANTIDX);
> +	lan_wr(ANA_VLAN_PORT_MASK_VLAN_PORT_MASK_SET(v->portmask),
> +	       lan9645x, ANA_VLAN_PORT_MASK);
> +	lan_wr(ANA_VLANACCESS_VLAN_TBL_CMD_SET(VLANACCESS_CMD_WRITE),
> +	       lan9645x, ANA_VLANACCESS);

[Severity: High]
[Finding: main-5-5]
[Sources: opus-5]
Should this three-register indirect transaction be serialized by a lock?

The MAC table engine in this driver is protected by mact_lock:

	struct mutex mact_lock; /* serialize mac table register access */

but the VLAN table access engine has no equivalent, and there is no
lockdep_assert_held() here.

lan9645x_vlan_set_hostmode() is now called from .port_setup:

lan9645x_port_setup()
    if (p->chip_port != lan9645x->npi)
        lan9645x_vlan_set_hostmode(p)
            lan9645x_vlan_hw_wr(p->lan9645x, HOST_PVID)

and .port_setup runs from the DSA probe path without rtnl_lock and
without fwd_domain_lock:

net/dsa/devlink.c:dsa_port_devlink_setup() {
	if (ds->ops->port_setup) {
		err = ds->ops->port_setup(ds, dp->index);
	...
}

dsa_port_devlink_setup() runs at the start of dsa_port_setup(), before
dsa_user_create() registers this port's netdev, while the netdevs of the
ports already processed are live. So while swp1..swpN are still going
through lan9645x_port_setup(), userspace can enslave swp0:

CPU0 (probe, no locks held)          CPU1 (rtnl, bridge join / vlan add)
lan9645x_vlan_set_hostmode()         lan9645x_port_vlan_add()
  lan9645x_vlan_hw_wr(.., 4095)        lan9645x_vlan_port_add_vlan()
                                         lan9645x_vlan_hw_wr(.., 100)

Can the two transactions interleave like this?

CPU1: lan_wr(V_INDEX=100,   ANA_VLANTIDX)
CPU0: lan_wr(V_INDEX=4095,  ANA_VLANTIDX)
CPU0: lan_wr(mask(4095),    ANA_VLAN_PORT_MASK)
CPU0: lan_wr(CMD_WRITE,     ANA_VLANACCESS)
CPU1: lan_wr(mask(100),     ANA_VLAN_PORT_MASK)
CPU1: lan_wr(CMD_WRITE,     ANA_VLANACCESS)

That would commit mask(100) into the HOST_PVID (4095) entry and leave
vid 100 without a member mask, i.e. either standalone ports lose their
isolation domain or the new VLAN blackholes traffic.

There is also the shadow update itself. lan9645x_vlan_set_hostmode() and
lan9645x_vlan_clear_hostmode() both do a non-atomic read-modify-write of
the same u32 bitfield word:

	p->lan9645x->vlans[HOST_PVID].portmask |= BIT(p->chip_port);
	...
	p->lan9645x->vlans[HOST_PVID].portmask &= ~BIT(p->chip_port);

portmask:10 shares the word with untagged:9 and the flag bits, and
lan9645x_port_bridge_join() calls lan9645x_vlan_clear_hostmode() under
fwd_domain_lock while lan9645x_port_setup() calls
lan9645x_vlan_set_hostmode() with no lock at all, so the lock sets do not
intersect. Can one of these updates be lost?

> +
> +	/* The VLAN access engine completes in a fixed ~1us vs the polling
> +	 * timeout of 100_000 us. A timeout here therefore likely means the
> +	 * register bus itself is dead, not that the VLAN op failed. There is no
> +	 * meaningful recovery at runtime, so this function logs via dev_err()
> +	 * and runtime callers discard the return value. Only
> +	 * lan9645x_vlan_init() treats this as fatal so that probe fails early
> +	 * on a broken bus.
> +	 */
> +	err = lan9645x_vlan_wait_for_completion(lan9645x);
> +	if (err)
> +		dev_err(lan9645x->dev, "Vlan set mask failed\n");
> +
> +	return err;
> +}

[ ... ]

> +int lan9645x_vlan_port_add_vlan(struct lan9645x_port *p, u16 vid, bool pvid,
> +				bool untagged, struct netlink_ext_ack *extack)
> +{

[ ... ]

> +	lan9645x_vlan_port_get_info(lan9645x, p->chip_port, &info);
> +
> +	if (info.untagged > 1 && info.tagged) {
> +		*v = old_vlan;
> +		p->pvid = old_pvid;
> +		NL_SET_ERR_MSG_MOD(extack, "Only support 1 untagged port VLAN");
> +		return -EBUSY;
> +	}

[Severity: Low]
[Finding: main-1-1]
[Sources: opus-5]
This isn't a bug, but could the commit message mention this restriction?

The commit message says only "Add VLAN support for VLAN-aware and
VLAN-unaware bridges", while this rejects an otherwise legal bridge
configuration: a second

	bridge vlan add dev swpN vid B untagged

fails with -EBUSY once the port already has one untagged VLAN plus at
least one tagged VLAN.

The changelog also notes an expected selftest failure with respect to
ctag/stag conformance, but that text is below the --- line and is dropped
when the patch is applied, so nothing about either limitation survives in
the tree.

> +
> +	lan9645x_vlan_hw_wr(lan9645x, vid);
> +	lan9645x_vlan_port_apply_ingress(p);
> +	lan9645x_vlan_port_apply_egress(p, &info);
> +
> +	return 0;
> +}

[ ... ]

> +void lan9645x_vlan_set_hostmode(struct lan9645x_port *p)
> +{
> +	p->vlan_aware = false;
> +	p->lan9645x->vlans[HOST_PVID].portmask |= BIT(p->chip_port);
> +	lan9645x_vlan_hw_wr(p->lan9645x, HOST_PVID);
> +	lan9645x_vlan_port_apply(p);
> +}
> +
> +void lan9645x_vlan_clear_hostmode(struct lan9645x_port *p)
> +{
> +	p->lan9645x->vlans[HOST_PVID].portmask &= ~BIT(p->chip_port);
> +	lan9645x_vlan_hw_wr(p->lan9645x, HOST_PVID);
> +	lan9645x_vlan_port_apply(p);
> +}

[ ... ]
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