Subject: Re: [PATCH net V3] virtio-net: validate features during probe

From: Jason Wang <[email-masked]>
Date: Thu, 20 Nov 2014 15:13:16 +0800

On 11/20/2014 03:02 PM, Michael S. Tsirkin wrote:
> On Thu, Nov 20, 2014 at 02:10:35PM +0800, Jason Wang wrote:
>> We currently trigger BUG when VIRTIO_NET_F_CTRL_VQ
>> is not set but one of features depending on it is.
>> That's not a friendly way to report errors to
>> hypervisors.
>> Let's check, and fail probe instead.
>>
>> Cc: Rusty Russell <[email-masked]>
>> Cc: Cornelia Huck <[email-masked]>
>> Cc: Wanlong Gao <[email-masked]>
>> Signed-off-by: Michael S. Tsirkin <[email-masked]>
>> Signed-off-by: Jason Wang <[email-masked]>
>
> Looks good, minor nits below:
>
>> ---
>> Changes from V2:
>> - only check the features for ctrl vq (this fix the real bug)
>> - better error message and simplify API
>> ---
>>  drivers/net/virtio_net.c | 37 +++++++++++++++++++++++++++++++++++++
>>  1 file changed, 37 insertions(+)
>>
>> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
>> index ec2a8b4..a6bcfce 100644
>> --- a/drivers/net/virtio_net.c
>> +++ b/drivers/net/virtio_net.c
>> @@ -1673,6 +1673,40 @@ static const struct attribute_group virtio_net_mrg_rx_group = {
>>  };
>>  #endif
>>  
>> +static bool virtnet_fail_on_feature(struct virtio_device *vdev,
>> +				    unsigned int fbit,
>> +				    const char *fname, const char *dname)
>> +{
>> +	if (!virtio_has_feature(vdev, fbit))
>> +		return false;
>> +
>> +	dev_err(&vdev->dev, "Hypervisor bug: advertise feature %s but not %s",
> Well we don't know it's a hypervisor. How about:
> Device bug: advertises feature %s but not %s.

Ok.
>> +		fname, dname);
>> +
>> +	return true;
>> +}
>> +
>> +#define VIRTNET_FAIL_ON(vdev, fbit, dbit)			\
>> +	virtnet_fail_on_feature(vdev, fbit, #fbit, #dbit)
> I would pass dbit directly, and supply a string from caller,
> instead if #dbit, this way it can be any string.

Right, this is better.
>> +
>> +static bool virtnet_validate_features(struct virtio_device *vdev)
>> +{
>> +	if (!virtio_has_feature(vdev, VIRTIO_NET_F_CTRL_VQ) &&
>> +	    (VIRTNET_FAIL_ON(vdev, VIRTIO_NET_F_CTRL_RX,
>> +			     VIRTIO_NET_F_CTRL_VQ) ||
>> +	     VIRTNET_FAIL_ON(vdev, VIRTIO_NET_F_CTRL_VLAN,
>> +			     VIRTIO_NET_F_CTRL_VQ) ||
>> +	     VIRTNET_FAIL_ON(vdev, VIRTIO_NET_F_GUEST_ANNOUNCE,
>> +			     VIRTIO_NET_F_TRL_VQ) ||
> Typo: VIRTIO_NET_F_CTRL_VQ.
>
>

Wil fix this and post V4.

Thanks