Re: [Qemu-devel] [PATCH v1 for-2.12 5/5] s390x/tcg: wire up STORE CHANNEL REPORT WORD

[David Hildenbrand <david@redhat.com>]

On 04.12.2017 18:58, Cornelia Huck wrote:
> On Mon, 4 Dec 2017 18:56:00 +0100
> David Hildenbrand <david@redhat.com> wrote:
> 
>> On 04.12.2017 18:53, Cornelia Huck wrote:
>>> On Mon, 4 Dec 2017 18:34:36 +0100
>>> David Hildenbrand <david@redhat.com> wrote:
>>>   
>>>> On 04.12.2017 18:22, Cornelia Huck wrote:  
>>>>> On Mon,  4 Dec 2017 13:55:05 +0100
>>>>> David Hildenbrand <david@redhat.com> wrote:
>>>>>     
>>>>>> We somehow missed that, new kernels require it.    
>>>>>
>>>>> Why _new_ kernels? I think we have unconditionally issued stcrw since
>>>>> back in 2.2?    
>>>>
>>>> Okay, the problem is then rather related to my setup. No ccw devices ->
>>>> no stcrw.
>>>>
>>>> How could we ever add ccw devices to a TCG guest then?  
>>>
>>> Hotplug never worked before your patches. Coldplug does not create
>>> machine checks and thus does not trigger the guest to do STCRW. (Only
>>> STSCH, in keeping with "all channel I/O acronyms look the same".)
>>>   
>>
>> But booting Fedora 26/27 without any involved hotplugs (therefore
>> machine checks) triggers a STCRW.
>>
>> That's how I originally found it. (I started playing with machine checks
>> after I had fedora 26/27 running)
>>
> 
> Confused. Do you have a backtrace? (Guest/host)
> 

Unfortunately not. Strange, I just tried to reproduce but can't trigger
it. Maybe aside effect from the other BUGs I have been fixing :)

So I'll just rephrase this to "CRW machine check handling requires STCRW."

-- 

Thanks,

David / dhildenb