Virtualization - Apr 2021 - [PATCH 3/3] vDPA/ifcvf: get_config_size should return dev specific config size

On Wed, Apr 14, 2021 at 05:18:32PM +0800, Zhu Lingshan
wrote:
>get_config_size() should return the size based on the decected
>device type.
>
>Signed-off-by: Zhu Lingshan <lingshan.zhu at intel.com>
>---
> drivers/vdpa/ifcvf/ifcvf_main.c | 11 ++++++++++-
> 1 file changed, 10 insertions(+), 1 deletion(-)
>
>diff --git a/drivers/vdpa/ifcvf/ifcvf_main.c
b/drivers/vdpa/ifcvf/ifcvf_main.c
>index 9b6a38b798fa..b48b9789b69e 100644
>--- a/drivers/vdpa/ifcvf/ifcvf_main.c
>+++ b/drivers/vdpa/ifcvf/ifcvf_main.c
>@@ -347,7 +347,16 @@ static u32 ifcvf_vdpa_get_vq_align(struct vdpa_device
*vdpa_dev)
>
> static size_t ifcvf_vdpa_get_config_size(struct vdpa_device *vdpa_dev)
> {
>-	return sizeof(struct virtio_net_config);
>+	struct ifcvf_hw *vf = vdpa_to_vf(vdpa_dev);
>+	size_t size;
>+
>+	if (vf->dev_type == VIRTIO_ID_NET)
>+		size = sizeof(struct virtio_net_config);
>+
>+	if (vf->dev_type == VIRTIO_ID_BLOCK)
>+		size = sizeof(struct virtio_blk_config);
>+
>+	return size;
I'm not familiar with the ifcvf details, but can it happen that the 
device is not block or net?

Should we set `size` to 0 by default to handle this case or are we sure 
it's one of the two?

Maybe we should add a comment or a warning message in this case, to 
prevent some analysis tool or compiler from worrying that `size` might 
be uninitialized.

I was thinking something like this:

	switch(vf->dev_type) {
	case VIRTIO_ID_NET:
		size = sizeof(struct virtio_net_config);
		break;
	case VIRTIO_ID_BLOCK:
		size = sizeof(struct virtio_blk_config);
		break;
	default:
		/* or WARN(1, "") if dev_warn() not apply */
		dev_warn(... , "virtio ID [0x%x] not supported\n")
		size = 0;

	}

Thanks,
Stefano

? 2021/4/15 ??4:12, Stefano Garzarella ??:
> On Wed, Apr 14, 2021 at 05:18:32PM +0800, Zhu Lingshan wrote:
>> get_config_size() should return the size based on the decected
>> device type.
>>
>> Signed-off-by: Zhu Lingshan <lingshan.zhu at intel.com>
>> ---
>> drivers/vdpa/ifcvf/ifcvf_main.c | 11 ++++++++++-
>> 1 file changed, 10 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/vdpa/ifcvf/ifcvf_main.c 
>> b/drivers/vdpa/ifcvf/ifcvf_main.c
>> index 9b6a38b798fa..b48b9789b69e 100644
>> --- a/drivers/vdpa/ifcvf/ifcvf_main.c
>> +++ b/drivers/vdpa/ifcvf/ifcvf_main.c
>> @@ -347,7 +347,16 @@ static u32 ifcvf_vdpa_get_vq_align(struct 
>> vdpa_device *vdpa_dev)
>>
>> static size_t ifcvf_vdpa_get_config_size(struct vdpa_device *vdpa_dev)
>> {
>> -??? return sizeof(struct virtio_net_config);
>> +??? struct ifcvf_hw *vf = vdpa_to_vf(vdpa_dev);
>> +??? size_t size;
>> +
>> +??? if (vf->dev_type == VIRTIO_ID_NET)
>> +??????? size = sizeof(struct virtio_net_config);
>> +
>> +??? if (vf->dev_type == VIRTIO_ID_BLOCK)
>> +??????? size = sizeof(struct virtio_blk_config);
>> +
>> +??? return size;
>
> I'm not familiar with the ifcvf details, but can it happen that the 
> device is not block or net?
>
> Should we set `size` to 0 by default to handle this case or are we 
> sure it's one of the two?
>
> Maybe we should add a comment or a warning message in this case, to 
> prevent some analysis tool or compiler from worrying that `size` might 
> be uninitialized.
>
> I was thinking something like this:
>
> ????switch(vf->dev_type) {
> ????case VIRTIO_ID_NET:
> ??????? size = sizeof(struct virtio_net_config);
> ??????? break;
> ????case VIRTIO_ID_BLOCK:
> ??????? size = sizeof(struct virtio_blk_config);
> ??????? break;
> ????default:
> ??????? /* or WARN(1, "") if dev_warn() not apply */
> ??????? dev_warn(... , "virtio ID [0x%x] not supported\n")
> ??????? size = 0;
>
> ????}
>
Yes, I agree.

Thanks

> Thanks,
> Stefano
>

On 4/15/2021 4:12 PM, Stefano Garzarella wrote:
> On Wed, Apr 14, 2021 at 05:18:32PM +0800, Zhu Lingshan wrote:
>> get_config_size() should return the size based on the decected
>> device type.
>>
>> Signed-off-by: Zhu Lingshan <lingshan.zhu at intel.com>
>> ---
>> drivers/vdpa/ifcvf/ifcvf_main.c | 11 ++++++++++-
>> 1 file changed, 10 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/vdpa/ifcvf/ifcvf_main.c 
>> b/drivers/vdpa/ifcvf/ifcvf_main.c
>> index 9b6a38b798fa..b48b9789b69e 100644
>> --- a/drivers/vdpa/ifcvf/ifcvf_main.c
>> +++ b/drivers/vdpa/ifcvf/ifcvf_main.c
>> @@ -347,7 +347,16 @@ static u32 ifcvf_vdpa_get_vq_align(struct 
>> vdpa_device *vdpa_dev)
>>
>> static size_t ifcvf_vdpa_get_config_size(struct vdpa_device *vdpa_dev)
>> {
>> -??? return sizeof(struct virtio_net_config);
>> +??? struct ifcvf_hw *vf = vdpa_to_vf(vdpa_dev);
>> +??? size_t size;
>> +
>> +??? if (vf->dev_type == VIRTIO_ID_NET)
>> +??????? size = sizeof(struct virtio_net_config);
>> +
>> +??? if (vf->dev_type == VIRTIO_ID_BLOCK)
>> +??????? size = sizeof(struct virtio_blk_config);
>> +
>> +??? return size;
>
> I'm not familiar with the ifcvf details, but can it happen that the 
> device is not block or net?
>
> Should we set `size` to 0 by default to handle this case or are we 
> sure it's one of the two?
>
> Maybe we should add a comment or a warning message in this case, to 
> prevent some analysis tool or compiler from worrying that `size` might 
> be uninitialized.
>
> I was thinking something like this:
>
> ????switch(vf->dev_type) {
> ????case VIRTIO_ID_NET:
> ??????? size = sizeof(struct virtio_net_config);
> ??????? break;
> ????case VIRTIO_ID_BLOCK:
> ??????? size = sizeof(struct virtio_blk_config);
> ??????? break;
> ????default:
> ??????? /* or WARN(1, "") if dev_warn() not apply */
> ??????? dev_warn(... , "virtio ID [0x%x] not supported\n")
> ??????? size = 0;
>
> ????}
>
> Thanks,
> Stefano
agree, will add this in V2

Thanks
>
> _______________________________________________
> Virtualization mailing list
> Virtualization at lists.linux-foundation.org
> https://lists.linuxfoundation.org/mailman/listinfo/virtualization