Subject: Re: [PATCH 2/2] virtio-net: fix buggy features advertised by host

From: Jason Wang <[email-masked]>
Date: Thu, 13 Nov 2014 14:45:54 +0800

On 11/13/2014 02:06 PM, Wanlong Gao wrote:
> On 11/13/2014 01:52 PM, Jason Wang wrote:
>> This patch tries to detect the possible buggy features advertised by host
>> and fix them. One example is booting virtio-net with only ctrl_vq disabled,
>> qemu may still advertise many features which depends on it. This will
>> trigger several BUG()s in virtnet_send_command().
>>
>> This patch utilizes the fix_features() method, and disables all features that
>> depends on ctrl_vq if it was not advertised.
>>
>> This fixes the crash when booting with ctrl_vq=off.
>>
>> Cc: Rusty Russell <[email-masked]>
>> Cc: Michael S. Tsirkin <[email-masked]>
>> Signed-off-by: Jason Wang <[email-masked]>
>> ---
>> Changes from V1:
>> - fix the cut-and-paste error
>> ---
>>  drivers/net/virtio_net.c | 35 +++++++++++++++++++++++++++++++++++
>>  1 file changed, 35 insertions(+)
>>
>> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
>> index ec2a8b4..6ce125e 100644
>> --- a/drivers/net/virtio_net.c
>> +++ b/drivers/net/virtio_net.c
>> @@ -1948,6 +1948,40 @@ static int virtnet_restore(struct virtio_device *vdev)
>>  }
>>  #endif
>>  
>> +static void virtnet_fix_features(struct virtio_device *dev)
>> +{
>> +	if (!virtio_has_feature(dev, VIRTIO_NET_F_CTRL_VQ)) {
>> +		if (virtio_has_feature(dev, VIRTIO_NET_F_CTRL_RX)) {
>> +			pr_warning("Disable VIRTIO_NET_F_CTRL_RX since host "
>> +				   "does not advertise VIRTIO_NET_F_CTRL_VQ");
>> +			virtio_disable_feature(dev, VIRTIO_NET_F_CTRL_RX);
>> +		}
>> +		if (virtio_has_feature(dev, VIRTIO_NET_F_CTRL_VLAN)) {
>> +			pr_warning("Disable VIRTIO_NET_F_CTRL_VLAN since host "
>> +				   "does not advertise VIRTIO_NET_F_CTRL_VQ");
>> +			virtio_disable_feature(dev, VIRTIO_NET_F_CTRL_VLAN);
>> +		}
>> +		if (virtio_has_feature(dev, VIRTIO_NET_F_GUEST_ANNOUNCE)) {
>> +			pr_warning("Disable VIRTIO_NET_F_GUEST_ANNOUNCE since "
>> +				   "host does not advertise "
>> +				   "VIRTIO_NET_F_CTRL_VQ");
>> +			virtio_disable_feature(dev,
>> +					       VIRTIO_NET_F_GUEST_ANNOUNCE);
>> +		}
>> +		if (virtio_has_feature(dev, VIRTIO_NET_F_MQ)) {
>> +			pr_warning("Disable VIRTIO_NET_F_MQ since host "
>> +				   "does not advertise VIRTIO_NET_F_CTRL_VQ");
>> +			virtio_disable_feature(dev, VIRTIO_NET_F_MQ);
>> +		}
>> +		if (virtio_has_feature(dev, VIRTIO_NET_F_CTRL_MAC_ADDR)) {
>> +			pr_warning("Disable VIRTIO_NET_F_CTRL_MAC_ADDR since "
>> +				   "host does not advertise "
>> +				   "VIRTIO_NET_F_CTRL_VQ");
>> +			virtio_disable_feature(dev, VIRTIO_NET_F_CTRL_MAC_ADDR);
>> +		}
>
> Can we use a feature array and check with one loop?  The current check looks so dup?
>
>
> Thanks,
> Wanlong Gao
>

Yes for sure. I will wait a little bit for the maintainers comment and
do it in next version.

Thanks