On Fri, Jul 16 2021, Pierre Morel <pmo...@linux.ibm.com> wrote: > On 7/16/21 11:22 AM, Cornelia Huck wrote: >> On Wed, Jul 14 2021, Pierre Morel <pmo...@linux.ibm.com> wrote: >> >>> Interception of the PTF instruction depending on the new >>> KVM_CAP_S390_CPU_TOPOLOGY KVM extension. >> >> Wasn't that the capability that you dropped? > > yes, > >> >> Is PTF supposed to be always intercepting? If that isn't configurable, >> wouldn't older QEMUs generate exceptions for it? I'm a bit confused. > > Yes, PTF generated an OPERATION exception on old QEMU, but was not used > by the guest if it has not the topology facility 11. > > So just as for STSI, I think we need the KVM_CAP_S390_CPU_TOPOLOGY I > dropped because otherwise, now that the kernel will advertise facility > 11, the guest will use it and it will get the exception that it should > not get.
Ok, makes sense.
