Re: [Qemu-devel] [PATCH 5/5] s390x/ccs: add ccw-tester emulated device

[Halil Pasic <pasic@linux.vnet.ibm.com>]

On 09/08/2017 04:01 AM, Dong Jia Shi wrote:
> * Cornelia Huck <cohuck@redhat.com> [2017-09-07 12:52:20 +0200]:
> 
>> On Thu, 7 Sep 2017 12:21:50 +0200
>> Halil Pasic <pasic@linux.vnet.ibm.com> wrote:
>>
>>> On 09/07/2017 10:08 AM, Cornelia Huck wrote:
>>>> On Thu, 7 Sep 2017 15:31:09 +0800
>>>> Dong Jia Shi <bjsdjshi@linux.vnet.ibm.com> wrote:
>>
>>>>> I'm thinking of a method these days:
>>>>> Could passing through an fully emulated ccw device (e.g. 3270), or a
>>>>> virtio ccw device, in the level 1 kvm guest to a level 2 guest be a test
>>>>> method for this?
>>>>>
>>>>> All of the CCWs will be translated to IDAL CCWs by vfio-ccw in the level
>>>>> 1 guest (which is the level 2 kvm host) and issued to the level 1 kvm
>>>>> host. So, those IDALs will eventually be handled by the emulated device,
>>>>> or the virtio ccw device, on the level 1 kvm host...
>>>>>
>>>>> Some days ago, one of my colleague tried the emulated 3270 passing
>>>>> through. She stucked with the problem that the level 1 kvm host handling
>>>>> a senseid IDAL ccw as a Direct ccw.
>>>>>
>>>>> Maybe I could try to pass through a virtio ccw device. I don't think of
>>>>> any obvious problem that would lead to fail. Any comment?
>>>>>  
>>>>
>>>> That actually looks like a good thing to try! Cool idea.
>>>>   
>>>
>>> I'm afraid that it would not work without some extra work.
>>> AFAIR Connie we said that the 3270 does not use any IDA, so
>>> I did not touch the 3270 emulation code in QEMU. To make
>>> the scenario viable one should convert the 3270 emulation
>>> to ccw data stream (unless the original implementation
>>> already took care of IDA, which I doubt).
>>
>> But the vfio-ccw code uses idals... no need to touch the 3270 emulation.
>>
> What Halil pointed out is that the ccw_cb implementation of 3270
> emulation does not take care of IDALs. This is true.
> 
> I can also do that right after this series, if Halil agrees.
> (The 3270 emulation authors are busy of other stuff these days. :()

Generally, yes I agree. If it's trivial I will probably do it myself
for v2. I need to do a v2 anyway.

Halil