Re: [XEN PATCH v15 2/4] x86/irq: allow setting IRQ permissions from GSI instead of pIRQ

["Chen, Jiqian" <Jiqian.Chen@xxxxxxx>]

On 2024/9/13 14:52, Jan Beulich wrote:
> On 13.09.2024 04:38, Chen, Jiqian wrote:
>> On 2024/9/12 18:51, Jan Beulich wrote:
>>> On 12.09.2024 12:34, Daniel P. Smith wrote:
>>>> On 9/11/24 02:58, Jiqian Chen wrote:
>>>>> @@ -237,6 +238,34 @@ long arch_do_domctl(
>>>>>           break;
>>>>>       }
>>>>>   
>>>>> +    case XEN_DOMCTL_gsi_permission:
>>>>> +    {
>>>>> +        int irq;
>>>>> +        unsigned int gsi = domctl->u.gsi_permission.gsi;
>>>>> +        uint32_t flags = domctl->u.gsi_permission.flags;
>>>>> +
>>>>> +        /* Check only valid bits are set */
>>>>> +        ret = -EINVAL;
>>>>> +        if ( flags & ~XEN_DOMCTL_GSI_ACTION_MASK )
>>>>> +            break;
>>>>> +
>>>>> +        ret = irq = gsi_2_irq(gsi);
>>>>
>>>> I was recently informed that a = b = c; form is not MISRA compliant. 
>>>> Since you just overwrite ret after the check, why not drop the 
>>>> assignment to ret and mae the next check against irq instead.
>>>
>>> The Misra concern is valid, yet the suggestion doesn't look to be quite
>>> matching what is needed. After all if we take ...
>>>
>>>>> +        if ( ret <= 0 )
>>>>> +            break;
>>>
>>> ... the "break" path, "ret" needs to be set. Plus there's the problem of
>>> "ret" being zero when exiting the function indicates success, yet this
>>> is an error path (requiring ret < 0). So overall perhaps
>>>
>>>          irq = gsi_2_irq(gsi);
>>>          if ( irq <= 0 )
>>>          {
>>>              ret = irq ?: -EACCES;
>>>              break;
>>>          }
>>>
>>> ?
>>
>> Yes, ret needs to be set. And since gsi_2_irq doesn't return 0(if irq is 0, 
>> gsi_2_irq returns -EINVAL).
>> Maybe below is enough?
>>         irq = gsi_2_irq(gsi);
>>         if ( irq < 0 )
>>         {
>>             ret = irq;
>>             break;
>>         }
> 
> My proposal was to cover that elsewhere we exclude IRQ0, and hence
> it would be good to be consistent here.
Got it, I will use your proposal in next version. Thanks.

> 
> Jan

-- 
Best regards,
Jiqian Chen.