netdev - Re: [PATCH net-next] virito-net: set queues after reset during xdp

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Message-ID: <2ecb6621-d118-14aa-e935-3ba09e2150f7@redhat.com>
Date:   Mon, 20 Feb 2017 11:47:46 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     "Michael S. Tsirkin" <mst@...hat.com>
Cc:     John Fastabend <john.fastabend@...il.com>,
        virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next] virito-net: set queues after reset during
 xdp_set



On 2017年02月19日 13:08, Michael S. Tsirkin wrote:
>>>> -	oxdp_qp = vi->xdp_queue_pairs;
>>>> -
>>>>    	/* Changing the headroom in buffers is a disruptive operation because
>>>>    	 * existing buffers must be flushed and reallocated. This will happen
>>>>    	 * when a xdp program is initially added or xdp is disabled by removing
>>>>    	 * the xdp program resulting in number of XDP queues changing.
>>>>    	 */
>>>>    	if (vi->xdp_queue_pairs != xdp_qp) {
>>>> -		vi->xdp_queue_pairs = xdp_qp;
>>>>    		err = virtnet_reset(vi);
>>>> -		if (err)
>>>> +		if (err) {
>>>> +			dev_warn(&dev->dev, "XDP reset failure.\n");
>>>>    			goto virtio_reset_err;
>>>> +		}
>>>> +		vi->xdp_queue_pairs = xdp_qp;
>>> But xdp_queue_pairs is being used to detect if we should allocate the XDP
>>> headroom. If we move it here do we have a set of buffers in the ring without
>>> the proper headroom when we assign the xdp program below?
>> Right, so how about passing xdp_queue_pairs as a parameter to
>> virtnet_reset(). Then virtnet_reset() can set it after _remove_vq_common()
>> but before virtnet_restore_up()?
>>
>> Thanks
> Jason, wouldn't you say it's cleaner to avoid resets?
> Would you be interested in completing this work:
>
> 20170207053455-mutt-send-email-mst@...nel.org
>
>

Yes, but this seems still need drop packets, is this acceptable?

Thanks