RE: [PATCH v4 net-next 04/15] net: enetc: add link speed message support to PF driver

[Claudiu Manoil]

NXP Confidential
> -----Original Message-----
> From: Wei Fang (OSS) <wei.fang@xxxxxxxxxxx>
> Sent: Wednesday, September 9, 2026 1:07 PM
[...]
> Subject: [PATCH v4 net-next 04/15] net: enetc: add link speed message
> support to PF driver
>
> From: Wei Fang <wei.fang@xxxxxxx>
>
> When a VF is driven by DPDK, its user space application needs accurate
> link speed information to make correct forwarding and configuration
> decisions. Add link speed message support so the PF replies with the
> current link speed when it receives a get-link-speed message from a VF.
>
> Use a new message class 0x81 (ENETC_MSG_CLASS_ID_LINK_SPEED). The
> PSI-to-VSI message is 16 bits: the high 8 bits are the class ID and the
> low 8 bits are the speed code, so up to 255 speed values are supported
> (ENETC_MSG_SPEED_MAX = 0xff). Instead of enumerating every speed above
> 5Gbps, use a formula so future high speeds need no enum or switch
> changes:
>
>   speed_code = (link_speed - 5000) / 1000 + ENETC_MSG_SPEED_5G
>
> The speed is read via phylink_ethtool_ksettings_get() rather than the
> speed passed to the mac_link_up() callback. When the MAC has a PCS
> layer, mac_link_up() reports the PCS link speed, which may differ from
> the external PHY link speed; phylink_ethtool_ksettings_get() returns the
> actual external link speed.
>
> Unlike the link status message (class 0x80), the get-link-speed message
> is only permitted for trusted VFs. Reading the speed requires the PF to
> take rtnl_lock(), so an untrusted VF spamming this query could cause
> rtnl_lock contention and starve routine network configuration on the
> host. An untrusted VF therefore receives a permission-deny response; a
> VF can be marked trusted via 'ip link set <pf> vf N trust on'.
>
> Note that link speed change notification is not supported yet.
>
> Signed-off-by: Wei Fang <wei.fang@xxxxxxx>

Reviewed-by: Claudiu Manoil <claudiu.manoil@xxxxxxx>