Re: [PATCH v5 2/2] s390/kvm: diagnose 318 handling

Collin Walling
2019-06-26T14:30:14Z

On 6/26/19 6:28 AM, Christian Borntraeger wrote:
>
>
> On 26.06.19 11:45, David Hildenbrand wrote:
>
>>
>> BTW. there is currently no mechanism to fake absence of diag318. Should
>> we have one? (in contrast, for CMMA we have, which is also a CPU feature)
>
> Yes, we want to be able to disable diag318 via a CPU model feature. That actually
> means that the kernel must not answer this if we disable it.
>
Correct. If the guest specifies diag318=off, then the instruction
shouldn't be executed (it is fenced off in the kernel by checking the
Read SCP Info bit).