On 3/14/24 17:44, Nina Schoetterl-Glausch wrote: > On Thu, 2024-03-14 at 16:54 +0100, Thomas Huth wrote: >> On 14/03/2024 16.49, Claudio Fontana wrote: >>> Hello Pierre, Ilya, >>> >>> I have a question on the s390x "topology" feature and examples. >>> >>> Mainly, is this feature supposed to be KVM accelerator-only, or also >>> available when using the TCG accelerator? >> >> Hi Claudio! >> >> Pierre left IBM, please CC: Nina with regards to s390x topology instead. >> >> But with regards to your question, I think I can answer that, too: The >> topology feature is currently working with KVM only, yes. It hasn't been >> implemented for TCG yet. >> >>> (docs/devel/s390-cpu-topology.rst vs >>> https://www.qemu.org/docs/master/system/s390x/cpu-topology.html) >>> >>> I see stsi-topology.c in target/s390x/kvm/ , so that part is clearly >>> KVM-specific, >>> >>> but in hw/s390x/cpu-topology.c I read: >>> >>> " >>> * - The first part in this file is taking care of all common functions >>> * used by KVM and TCG to create and modify the topology. > > What Thomas said. Read this as the code in file being independent with > respect to the accelerator, > it's just that TCG support is missing. > > [...] >>> >>> So I would assume this is KVM-only, but then in the "Examples" section >>> below I see the example: >>> >>> " >>> $ qemu-system-s390x -m 2G \ >>> -cpu gen16b,ctop=on \ > > TCG doesn't support this cpu ^ and so will refuse to run. > >>> -smp cpus=5,sockets=8,cores=4,maxcpus=32 \ > > When running with TCG, drawers & books are supported by -smp also, but well, > you cannot do anything > with that. > > [...] >> >
Thank you for your responses Thomas and Nina, I have just sent a patch that tries to make it even more explicit. "[PATCH] docs/s390: clarify even more that cpu-topology is KVM-only" Thanks, Claudio
