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

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Message-ID: <CY4PR2101MB0867C9ED162F61A82CEB6CCACA290@CY4PR2101MB0867.namprd21.prod.outlook.com>
Date:   Wed, 15 Nov 2017 16:05:24 +0000
From:   Haiyang Zhang <haiyangz@...rosoft.com>
To:     Vitaly Kuznetsov <vkuznets@...hat.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "devel@...uxdriverproject.org" <devel@...uxdriverproject.org>,
        KY Srinivasan <kys@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        "Mohammed Gamal" <mmorsy@...hat.com>
Subject: RE: [PATCH net v2] hv_netvsc: preserve hw_features on
 mtu/channels/ringparam changes



> -----Original Message-----
> From: Vitaly Kuznetsov [mailto:vkuznets@...hat.com]
> Sent: Wednesday, November 15, 2017 9:13 AM
> To: netdev@...r.kernel.org
> Cc: linux-kernel@...r.kernel.org; devel@...uxdriverproject.org; KY
> Srinivasan <kys@...rosoft.com>; Haiyang Zhang
> <haiyangz@...rosoft.com>; Stephen Hemminger
> <sthemmin@...rosoft.com>; Mohammed Gamal <mmorsy@...hat.com>
> 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@...hat.com>

Reviewed-by: Haiyang Zhang <haiyangz@...rosoft.com>

Thank you!