Re: [PATCH 3/3] vDPA/ifcvf: get_config_size should return dev specific config size

From: Stefano Garzarella <sgarzare@redhat.com>
To: Zhu Lingshan <lingshan.zhu@linux.intel.com>
Cc: virtualization@lists.linux-foundation.org
Subject: Re: [PATCH 3/3] vDPA/ifcvf: get_config_size should return dev specific config size
Date: Thu, 15 Apr 2021 10:33:39 +0200	[thread overview]
Message-ID: <20210415083339.4whghntxtodt24xz@steredhat> (raw)
In-Reply-To: <406df891-246e-4eaf-030c-192d49813af0@linux.intel.com>

On Thu, Apr 15, 2021 at 04:23:15PM +0800, Zhu Lingshan wrote:
>
>
>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@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

Great, maybe something similar also in patch 2/3 for `features` in 
ifcvf_vdpa_get_features().

Thanks,
Stefano

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