RE: [PATCH net v2] hv_netvsc: preserve hw_features on mtu/channels/ringparam changes

[Haiyang Zhang]

> -----Original Message-----
> From: Vitaly Kuznetsov [mailto:vkuznets@xxxxxxxxxx]
> Sent: Wednesday, November 15, 2017 9:13 AM
> To: netdev@xxxxxxxxxxxxxxx
> Cc: linux-kernel@xxxxxxxxxxxxxxx; devel@xxxxxxxxxxxxxxxxxxxxxx; KY
> Srinivasan <kys@xxxxxxxxxxxxx>; Haiyang Zhang
> <haiyangz@xxxxxxxxxxxxx>; Stephen Hemminger
> <sthemmin@xxxxxxxxxxxxx>; Mohammed Gamal <mmorsy@xxxxxxxxxx>
> Subject: [PATCH net v2] hv_netvsc: preserve hw_features on
> mtu/channels/ringparam changes
> 
> rndis_filter_device_add() is called both from netvsc_probe() when we
> initially create the device and from set channels/mtu/ringparam
> routines where we basically remove the device and add it back.
> 
> hw_features is reset in rndis_filter_device_add() and filled with
> host data. However, we lose all additional flags which are set outside
> of the driver, e.g. register_netdevice() adds NETIF_F_SOFT_FEATURES and
> many others.
> 
> Unfortunately, calls to rndis_{query_hwcaps(), _set_offload_params()}
> calls cannot be avoided on every RNDIS reset: host expects us to set
> required features explicitly. Moreover, in theory hardware capabilities
> can change and we need to reflect the change in hw_features.
> 
> Reset net->hw_features bits according to host data in
> rndis_netdev_set_hwcaps(), clear corresponding feature bits
> from net->features in case some features went missing (will never happen
> in real life I guess but let's be consistent).
> 
> Signed-off-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>

Reviewed-by: Haiyang Zhang <haiyangz@xxxxxxxxxxxxx>

Thank you!