Re: [qemu-s390x] [PATCH for-4.1 1/2] s390x/pci: add some fallthrough annotations

[Christian Borntraeger]

On 17.07.19 10:54, Cornelia Huck wrote:
> On Tue, 16 Jul 2019 14:34:22 -0400
> Collin Walling <address@hidden> wrote:
> 
>> On 7/16/19 11:20 AM, Cornelia Huck wrote:
>>> On Wed, 10 Jul 2019 10:20:41 +0200
>>> Cornelia Huck <address@hidden> wrote:
>>>   
>>>> On Tue, 9 Jul 2019 18:55:34 -0400
>>>> Collin Walling <address@hidden> wrote:
>>>>  
>>>>> On 7/8/19 9:23 AM, Christian Borntraeger wrote:  
>>>>>>
>>>>>>
>>>>>> On 08.07.19 14:54, Cornelia Huck wrote:  
>>>>>>> According to the comment, the bits are supposed to accumulate.
>>>>>>>
>>>>>>> Reported-by: Stefan Weil <address@hidden>
>>>>>>> Fixes: 5d1abf234462 ("s390x/pci: enforce zPCI state checking")
>>>>>>> Signed-off-by: Cornelia Huck <address@hidden>  
>>>>>>
>>>>>> This patch does not change behaviour, so it is certainly not wrong.
>>>>>>
>>>>>> So lets have a look at if the bug report was actually a real bug or
>>>>>> just a missing annotation.
>>>>>>        
>>>>>>> ---
>>>>>>>    hw/s390x/s390-pci-inst.c | 2 ++
>>>>>>>    1 file changed, 2 insertions(+)
>>>>>>>
>>>>>>> diff --git a/hw/s390x/s390-pci-inst.c b/hw/s390x/s390-pci-inst.c
>>>>>>> index 61f30b8e55d2..00235148bed7 100644
>>>>>>> --- a/hw/s390x/s390-pci-inst.c
>>>>>>> +++ b/hw/s390x/s390-pci-inst.c
>>>>>>> @@ -1209,8 +1209,10 @@ int stpcifc_service_call(S390CPU *cpu, uint8_t 
>>>>>>> r1, uint64_t fiba, uint8_t ar,
>>>>>>>         * FH Enabled bit is set to one in states of ENABLED, BLOCKED or 
>>>>>>> ERROR. */
>>>>>>>        case ZPCI_FS_ERROR:
>>>>>>>            fib.fc |= 0x20;
>>>>>>> +        /* fallthrough */  
>>>>>>
>>>>>> This is correct, in case of an error we are also blocked.
>>>>>>        
>>>>>
>>>>> Agreed. This is definitely correct based on our architecture.
>>>>>      
>>>>>>>        case ZPCI_FS_BLOCKED:
>>>>>>>            fib.fc |= 0x40;
>>>>>>> +        /* fallthrough */  
>>>>>>
>>>>>> I think this is also correct, but  it would be good if Collin could 
>>>>>> verify.
>>>>>>        
>>>>>
>>>>> I failed to find anything to support setting the function control
>>>>> enabled bit when the function state is in error / blocked. I'm
>>>>> assuming this might be some QEMU hack to get things working? I'll have
>>>>> to dive further to understand why this was done this way, as it doesn't
>>>>> align with how the s390x architecture is documented. It's confusing.  
>>>>
>>>> Might this also be a real issue? Not matching the architecture is not a
>>>> good sign...  
>>>
>>> Friendly ping. If we still want to have this patch or a fix in 4.1, we
>>> need to find out soon...
>>>   
>>
>> Let's take it for now.
>>
>> Acked-by: Collin Walling <address@hidden>
>>
> 
> Just to be clear: You think that the current code is correct AFAYCS?
 
I also looked into this again. 
There is a possibility to also be in disabled state.
>From what I can see, it makes sense that blocked and error belong to the 
>enable state
so the patch seems correct.