Am 02.09.22 um 09:55 schrieb Pierre Morel:
Hi, The implementation of the CPU Topology in QEMU has been drastically modified since the last patch series and the number of LOCs has been greatly reduced. Unnecessary objects have been removed, only a single S390Topology object is created to support migration and reset. Also a documentation has been added to the series. To use these patches, you will need Linux V6-rc1 or newer. Mainline patches needed are: f5ecfee94493 2022-07-20 KVM: s390: resetting the Topology-Change-Report 24fe0195bc19 2022-07-20 KVM: s390: guest support for topology function 0130337ec45b 2022-07-20 KVM: s390: Cleanup ipte lock access and SIIF fac.. Currently this code is for KVM only, I have no idea if it is interesting to provide a TCG patch. If ever it will be done in another series. To have a better understanding of the S390x CPU Topology and its implementation in QEMU you can have a look at the documentation in the last patch. New in this series ================== s390x/cpus: Make absence of multithreading clear This patch makes clear that CPU-multithreading is not supported in the guest. s390x/cpu topology: core_id sets s390x CPU topology This patch uses the core_id to build the container topology and the placement of the CPU inside the container. s390x/cpu topology: reporting the CPU topology to the guest This patch is based on the fact that the CPU type for guests is always IFL, CPUs are always dedicated and the polarity is always horizontal. This may change in the future. hw/core: introducing drawer and books for s390x s390x/cpu: reporting drawers and books topology to the guest These two patches extend the topology handling to add two new containers levels above sockets: books and drawers. The subject of the last patches is clear enough (I hope). Regards, Pierre Pierre Morel (10): s390x/cpus: Make absence of multithreading clear s390x/cpu topology: core_id sets s390x CPU topology s390x/cpu topology: reporting the CPU topology to the guest hw/core: introducing drawer and books for s390x s390x/cpu: reporting drawers and books topology to the guest s390x/cpu_topology: resetting the Topology-Change-Report s390x/cpu_topology: CPU topology migration target/s390x: interception of PTF instruction s390x/cpu_topology: activating CPU topology
Do we really need a machine property? As far as I can see, old QEMU cannot activate the ctop facility with old and new kernel unless it enables CAP_S390_CPU_TOPOLOGY. I do get oldqemu .... -cpu z14,ctop=on qemu-system-s390x: Some features requested in the CPU model are not available in the configuration: ctop With the newer QEMU we can. So maybe we can simply have a topology (and then a cpu model feature) in new QEMUs and non in old. the cpu model would then also fence migration from enabled to disabled.
