On 03.04.19 13:28, Christian Borntraeger wrote: > > > On 02.04.19 19:46, Collin Walling wrote: >> Execution of DIAGNOSE 0x318 is fenced by checking an SCLP bit >> for the availability of hardware support for the instruction. >> >> In order to support this instruction for a KVM/QEMU guest, we >> would need to provide modifications to the SCLP Read SCP Info >> data, which will in turn reduce the maximum number of CPUs that >> may be provided to the guest. This issue introduces compatability >> and legacy concerns. >> >> Let's circumvent this issue by removing the bit check and blindly >> executing the instruction. An exception table rule is in place to >> catch the case where hardware does not support this instruction. > > > No, please keep the check. We have to extend the read scp field anyway > for future extensions. Wasn't there already an SCLP-way of telling the guest that the read-scp info response is bigger than 4k? Somehow rings a bell ... -- Thanks, David / dhildenb
