From mboxrd@z Thu Jan  1 00:00:00 1970
From: Vitaly Kuznetsov <vkuznets@redhat.com>
Subject: Re: [PATCH net] hv_netvsc: preserve hw_features on mtu/channels/ringparam changes
Date: Tue, 14 Nov 2017 17:58:23 +0100
Message-ID: <871sl0u79s.fsf@vitty.brq.redhat.com>
References: <20171114152205.10943-1-vkuznets@redhat.com>
        <20171114083457.5ec8c4f0@xeon-e3>
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Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
        devel@linuxdriverproject.org,
        "K. Y. Srinivasan" <kys@microsoft.com>,
        Haiyang Zhang <haiyangz@microsoft.com>,
        Stephen Hemminger <sthemmin@microsoft.com>,
        Mohammed Gamal <mmorsy@redhat.com>
To: Stephen Hemminger <stephen@networkplumber.org>
Return-path: <linux-kernel-owner@vger.kernel.org>
In-Reply-To: <20171114083457.5ec8c4f0@xeon-e3> (Stephen Hemminger's message of
        "Tue, 14 Nov 2017 08:34:57 -0800")
Sender: linux-kernel-owner@vger.kernel.org
List-Id: netdev.vger.kernel.org

Stephen Hemminger <stephen@networkplumber.org> writes:

> On Tue, 14 Nov 2017 16:22:05 +0100
> Vitaly Kuznetsov <vkuznets@redhat.com> wrote:
>
> Yes, this looks like a real issue.
>
>> +	/* Query hardware capabilities if we're called from netvsc_probe() */
>> +	if (!net->hw_features) {
>> +		ret = rndis_netdev_set_hwcaps(net_device, rndis_device);
>> +		if (ret != 0)
>> +			goto err_dev_remv;
>> +	}
>> +
>
> Rather than conditional behavior in rndis_filter_device_add, it would be cleaner
> to make the call to get hardware capabilities there.
>
> Please respin and make the query of host a separate function.

You mean call rndis_netdev_set_hwcaps() from netvsc_probe()? Will do.

One question though: in case we'll be avoiding
rndis_filter_set_offload_params() call on mtu/channels/ringparam
changes -- can we trust the host to preserve what was there before the
RNDIS reset? In case not we'll have to untangle what is
rndis_netdev_set_hwcaps() in my patch splitting it into two: hw_features
setup and rndis_filter_set_offload_params() and leaving the later in
rndis_filter_device_add().

Thanks,

-- 
  Vitaly