Linux Virtualization - Nov 2014 - [PATCH net V3] virtio-net: validate features during probe

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 <rusty at rustcorp.com.au>
Cc: Cornelia Huck <cornelia.huck at de.ibm.com>
Cc: Wanlong Gao <gaowanlong at cn.fujitsu.com>
Signed-off-by: Michael S. Tsirkin <mst at redhat.com>
Signed-off-by: Jason Wang <jasowang at redhat.com>
---
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",
+		fname, dname);
+
+	return true;
+}
+
+#define VIRTNET_FAIL_ON(vdev, fbit, dbit)			\
+	virtnet_fail_on_feature(vdev, fbit, #fbit, #dbit)
+
+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) ||
+	     VIRTNET_FAIL_ON(vdev, VIRTIO_NET_F_MQ, VIRTIO_NET_F_CTRL_VQ) ||
+	     VIRTNET_FAIL_ON(vdev, VIRTIO_NET_F_CTRL_MAC_ADDR,
+			     VIRTIO_NET_F_CTRL_VQ))) {
+		return false;
+	}
+
+	return true;
+}
+
 static int virtnet_probe(struct virtio_device *vdev)
 {
 	int i, err;
@@ -1680,6 +1714,9 @@ static int virtnet_probe(struct virtio_device *vdev)
 	struct virtnet_info *vi;
 	u16 max_queue_pairs;
 
+	if (!virtnet_validate_features(vdev))
+		return -EINVAL;
+
 	/* Find if host supports multiqueue virtio_net device */
 	err = virtio_cread_feature(vdev, VIRTIO_NET_F_MQ,
 				   struct virtio_net_config,
-- 
1.9.1

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 <rusty at rustcorp.com.au>
> Cc: Cornelia Huck <cornelia.huck at de.ibm.com>
> Cc: Wanlong Gao <gaowanlong at cn.fujitsu.com>
> Signed-off-by: Michael S. Tsirkin <mst at redhat.com>
> Signed-off-by: Jason Wang <jasowang at redhat.com>

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.
> +		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.
> +
> +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.
> +	     VIRTNET_FAIL_ON(vdev, VIRTIO_NET_F_MQ, VIRTIO_NET_F_CTRL_VQ) ||
> +	     VIRTNET_FAIL_ON(vdev, VIRTIO_NET_F_CTRL_MAC_ADDR,
> +			     VIRTIO_NET_F_CTRL_VQ))) {
> +		return false;
> +	}
> +
> +	return true;
> +}
> +
>  static int virtnet_probe(struct virtio_device *vdev)
>  {
>  	int i, err;
> @@ -1680,6 +1714,9 @@ static int virtnet_probe(struct virtio_device *vdev)
>  	struct virtnet_info *vi;
>  	u16 max_queue_pairs;
>  
> +	if (!virtnet_validate_features(vdev))
> +		return -EINVAL;
> +
>  	/* Find if host supports multiqueue virtio_net device */
>  	err = virtio_cread_feature(vdev, VIRTIO_NET_F_MQ,
>  				   struct virtio_net_config,
> -- 
> 1.9.1

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 <rusty at rustcorp.com.au>
>> Cc: Cornelia Huck <cornelia.huck at de.ibm.com>
>> Cc: Wanlong Gao <gaowanlong at cn.fujitsu.com>
>> Signed-off-by: Michael S. Tsirkin <mst at redhat.com>
>> Signed-off-by: Jason Wang <jasowang at redhat.com>
>
> 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