Re: [PATCH v1 2/8] s390/sclp: check sccb len before filling in data

[Collin Walling <walling@linux.ibm.com>]

On 5/12/20 12:24 PM, Cornelia Huck wrote:
> On Tue, 12 May 2020 12:16:45 -0400
> Collin Walling <walling@linux.ibm.com> wrote:
> 
>> On 5/12/20 12:01 PM, Cornelia Huck wrote:
>>> On Mon, 11 May 2020 17:02:06 +0200
>>> David Hildenbrand <david@redhat.com> wrote:
>>>    
>>>> On 11.05.20 16:50, Janosch Frank wrote:
>>>>> On 5/11/20 4:44 PM, David Hildenbrand wrote:
>>>>>> On 11.05.20 16:36, Janosch Frank wrote:
>>>>>>> On 5/9/20 1:08 AM, Collin Walling wrote:
>>>>>>>> The SCCB must be checked for a sufficient length before it is filled
>>>>>>>> with any data. If the length is insufficient, then the SCLP command
>>>>>>>> is suppressed and the proper response code is set in the SCCB header.
>>>>>>>>
>>>>>>>> Signed-off-by: Collin Walling <walling@linux.ibm.com>
>>>>>>>
>>>>>>> Fixes tag?
>>>
>>> Probably
>>>
>>> Fixes: 832be0d8a3bb ("s390x: sclp: Report insufficient SCCB length")
>>>
>>> ?
>>>    
>>
>> Sounds reasonable. This patch doesn't fix any explicitly-known bugs
>> AFAIK. The s390 Linux kernel is hard-coded to use a 4K size SCCB when
>> executing these commands.
>>
>> I suppose this could introduce a bug if things change in the Linux
>> kernel or if some other OS wants to use this command. That should be
>> enough of a justification, right? (Just want to make sure I understand
>> the use of the tag correctly).
> 
> Yes; from the description of how this is supposed to work it fixes
> architectural conformance, not a bug that is triggered by today's guest
> systems.
> 
> [Usage of the Fixes: tag in QEMU is not quite as essential as in Linux,
> as we don't do the numerous, big stable updates here; I don't think
> this is stable material, but we can certainly record where this was
> introduced.]
> 
> 

Makes sense to me, thanks for the info and commit ID! I'll add it to the
message for next round.

-- 
--
Regards,
Collin

Stay safe and stay healthy