linux-kernel - Re: [PATCH 1/6] vdpa: fix improper error message when adding vdpa dev

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Message-ID: <d48c157e-73d0-17c6-85c9-8753643ed03b@oracle.com>
Date:   Tue, 31 Jan 2023 14:51:03 -0800
From:   Si-Wei Liu <si-wei.liu@...cle.com>
To:     Eli Cohen <elic@...dia.com>, mst@...hat.com, jasowang@...hat.com,
        parav@...dia.com
Cc:     virtualization@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/6] vdpa: fix improper error message when adding vdpa dev



On 1/31/2023 3:42 AM, Eli Cohen wrote:
>
> On 30/01/2023 22:30, Si-Wei Liu wrote:
>> In below example, before the fix, mtu attribute is supported
>> by the parent mgmtdev, but the error message showing "All
>> provided are not supported" is just misleading.
>>
>> $ vdpa mgmtdev show
>> vdpasim_net:
>>    supported_classes net
>>    max_supported_vqs 3
>>    dev_features MTU MAC CTRL_VQ CTRL_MAC_ADDR ANY_LAYOUT VERSION_1 
>> ACCESS_PLATFORM
>>
>> $ vdpa dev add mgmtdev vdpasim_net name vdpasim0 mtu 5000 max_vqp 2
>> Error: vdpa: All provided attributes are not supported.
>> kernel answers: Operation not supported
>>
>> After fix, the relevant error message will be like:
>>
>> $ vdpa dev add mgmtdev vdpasim_net name vdpasim0 mtu 5000 max_vqp 2
>> Error: vdpa: Some provided attributes are not supported.
>> kernel answers: Operation not supported
>>
>> $ vdpa dev add mgmtdev vdpasim_net name vdpasim0 max_vqp 2
>> Error: vdpa: All provided attributes are not supported.
>> kernel answers: Operation not supported
>>
>> Signed-off-by: Si-Wei Liu <si-wei.liu@...cle.com>
>> Acked-by: Jason Wang <jasowang@...hat.com>
>> ---
>>   drivers/vdpa/vdpa.c | 9 ++++++++-
>>   1 file changed, 8 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/vdpa/vdpa.c b/drivers/vdpa/vdpa.c
>> index 8ef7aa1..5e57935 100644
>> --- a/drivers/vdpa/vdpa.c
>> +++ b/drivers/vdpa/vdpa.c
>> @@ -622,13 +622,20 @@ static int vdpa_nl_cmd_dev_add_set_doit(struct 
>> sk_buff *skb, struct genl_info *i
>>           err = PTR_ERR(mdev);
>>           goto err;
>>       }
>> -    if ((config.mask & mdev->config_attr_mask) != config.mask) {
>> +    if (config.mask && (config.mask & mdev->config_attr_mask) == 0) {
> If config.mask is zero than the condition is false even without the 
> change so I don't see why is this change needed.
This way it spews error message when none of the attributes provided by 
user is supported by device.
I can remove the check if improving error message for the other check 
right below, but that is the expected conditional if the same error 
message has to be kept.

>> NL_SET_ERR_MSG_MOD(info->extack,
>>                      "All provided attributes are not supported");
>>           err = -EOPNOTSUPP;
>>           goto err;
>>       }
>>   +    if ((config.mask & mdev->config_attr_mask) != config.mask) {
>> +        NL_SET_ERR_MSG_MOD(info->extack,
>> +                   "Some provided attributes are not supported");
> Changing the message is needed but maybe list the attributes that were 
> specified but are not supported?
If you can live with numeric representing the attributes instead of 
straight attribute string, certainly I can do that. Or else I anticipate 
userspace to query and fail the command rather than present attribute 
strings in kernel.

-Siwei

>> +        err = -EOPNOTSUPP;
>> +        goto err;
>> +    }
>> +
>>       err = mdev->ops->dev_add(mdev, name, &config);
>>   err:
>>       up_write(&vdpa_dev_lock);