[PATCH V2] mlx5: vdpa: fix possible uninitialized var

[PATCH V2] mlx5: vdpa: fix possible uninitialized var

[Jason Wang]

When compiling with -Werror=maybe-uninitialized, gcc may complains the
possible uninitialized umem. Since the callers won't pass value other
than 1 to 3, making 3 as default to fix the compiler warning.

Signed-off-by: Jason Wang <jasowang@redhat.com>
---
 drivers/vdpa/mlx5/net/mlx5_vnet.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/vdpa/mlx5/net/mlx5_vnet.c b/drivers/vdpa/mlx5/net/mlx5_vnet.c
index f1d54814db97..07ccc61cd6f6 100644
--- a/drivers/vdpa/mlx5/net/mlx5_vnet.c
+++ b/drivers/vdpa/mlx5/net/mlx5_vnet.c
@@ -703,7 +703,7 @@ static void umem_destroy(struct mlx5_vdpa_net *ndev, struct mlx5_vdpa_virtqueue
 	case 2:
 		umem = &mvq->umem2;
 		break;
-	case 3:
+	default:
 		umem = &mvq->umem3;
 		break;
 	}
-- 
2.25.1

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Re: [PATCH V2] mlx5: vdpa: fix possible uninitialized var

[Michael S. Tsirkin]

On Thu, Jan 14, 2021 at 03:09:04PM +0800, Jason Wang wrote:
> When compiling with -Werror=maybe-uninitialized, gcc may complains the
> possible uninitialized umem. Since the callers won't pass value other
> than 1 to 3, making 3 as default to fix the compiler warning.
> 
> Signed-off-by: Jason Wang <jasowang@redhat.com>

Of course if it's actually something else this is not DTRT ...
As long as we worry about this warning, let's have defence in depth:
  	case 3:
  		umem = &mvq->umem3;
  		break;
 +	default:
 +		umem = NULL;
 +              BUG();
 +		break;


> ---
>  drivers/vdpa/mlx5/net/mlx5_vnet.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/vdpa/mlx5/net/mlx5_vnet.c b/drivers/vdpa/mlx5/net/mlx5_vnet.c
> index f1d54814db97..07ccc61cd6f6 100644
> --- a/drivers/vdpa/mlx5/net/mlx5_vnet.c
> +++ b/drivers/vdpa/mlx5/net/mlx5_vnet.c
> @@ -703,7 +703,7 @@ static void umem_destroy(struct mlx5_vdpa_net *ndev, struct mlx5_vdpa_virtqueue
>  	case 2:
>  		umem = &mvq->umem2;
>  		break;
> -	case 3:
> +	default:
>  		umem = &mvq->umem3;
>  		break;
>  	}
> -- 
> 2.25.1

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Re: [PATCH V2] mlx5: vdpa: fix possible uninitialized var

[Jason Wang]

On 2021/1/17 下午6:30, Michael S. Tsirkin wrote:
> On Thu, Jan 14, 2021 at 03:09:04PM +0800, Jason Wang wrote:
>> When compiling with -Werror=maybe-uninitialized, gcc may complains the
>> possible uninitialized umem. Since the callers won't pass value other
>> than 1 to 3, making 3 as default to fix the compiler warning.
>>
>> Signed-off-by: Jason Wang <jasowang@redhat.com>
> Of course if it's actually something else this is not DTRT ...


It breaks some donw stream build (which mandates 
-Werror=maybe-uninitialized)


> As long as we worry about this warning, let's have defence in depth:
>    	case 3:
>    		umem = &mvq->umem3;
>    		break;
>   +	default:
>   +		umem = NULL;
>   +              BUG();
>   +		break;


Checkpatch doesn't like this:

WARNING: Avoid crashing the kernel - try using WARN_ON & recovery code 
rather than BUG() or BUG_ON()
#20: FILE: drivers/vdpa/mlx5/net/mlx5_vnet.c:695:
+        BUG();

But if you stick, I can go this way.

Thanks


>
>> ---
>>   drivers/vdpa/mlx5/net/mlx5_vnet.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/vdpa/mlx5/net/mlx5_vnet.c b/drivers/vdpa/mlx5/net/mlx5_vnet.c
>> index f1d54814db97..07ccc61cd6f6 100644
>> --- a/drivers/vdpa/mlx5/net/mlx5_vnet.c
>> +++ b/drivers/vdpa/mlx5/net/mlx5_vnet.c
>> @@ -703,7 +703,7 @@ static void umem_destroy(struct mlx5_vdpa_net *ndev, struct mlx5_vdpa_virtqueue
>>   	case 2:
>>   		umem = &mvq->umem2;
>>   		break;
>> -	case 3:
>> +	default:
>>   		umem = &mvq->umem3;
>>   		break;
>>   	}
>> -- 
>> 2.25.1

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