Re: [PATCH 5/5] qemu: Prefer -numa cpu over -numa node,cpus=

On Wed, Oct 20, 2021 at 13:07:59 +0200, Michal Prívozník wrote: > On 10/6/21 3:32 PM, Igor Mammedov wrote: >> On Thu, 30 Sep 2021 14:08:34 +0200 >> Peter Krempa <pkrempa(a)redhat.com&gt; wrote: [...] > 2) In my experiments I try to mimic what libvirt does. Here's my cmd > line: > > qemu-system-x86_64 \ > -S \ > -preconfig \ > -cpu host \ > -smp 120,sockets=2,dies=3,cores=4,threads=5 \ > -object '{"qom-type":"memory-backend-memfd","id":"ram-node0","size":4294967296,"host-nodes":[0],"policy":"bind"}' \ > -numa node,nodeid=0,memdev=ram-node0 \ > -no-user-config \ > -nodefaults \ > -no-shutdown \ > -qmp stdio > > and here is my QMP log: > > {"QMP": {"version": {"qemu": {"micro": 50, "minor": 1, "major": 6}, "package": "v6.1.0-1552-g362534a643"}, "capabilities": ["oob"]}} > > {"execute":"qmp_capabilities"} > {"return": {}} > > {"execute":"query-hotpluggable-cpus"} > {"return": [{"props": {"core-id": 3, "thread-id": 4, "die-id": 2, "socket-id": 1}, "vcpus-count": 1, "type": "host-x86_64-cpu"}, {"props": {"core-id": 3, "thread-id": 3, "die-id": 2, "socket-id": 1}, "vcpus-count": 1, "type": "host-x86_64-cpu"}, {"props": {"core-id": 3, "thread-id": 2, "die-id": 2, "socket-id": 1}, "vcpus-count": 1, "type": "host-x86_64-cpu"}, {"props": {"core-id": 3, "thread-id": 1, "die-id": 2, "socket-id": 1}, "vcpus-count": 1, "type": "host-x86_64-cpu"}, {"props": {"core-id": 3, "thread-id": 0, "die-id": 2, "socket-id": 1}, "vcpus-count": 1, "type": "host-x86_64-cpu"}, {"props": {"core-id": 2, "thread-id": 4, "die-id": 2, "socket-id": 1}, "vcpus-count": 1, "type": "host-x86_64-cpu"}, > <snip/> > {"props": {"core-id": 0, "thread-id": 0, "die-id": 0, "socket-id": 0}, "vcpus-count": 1, "type": "host-x86_64-cpu"}]} > > > I can see that query-hotpluggable-cpus returns an array. Can I safely > assume that vCPU ID == index in the array? I mean, if I did have -numa No, this assumption would be incorrect on the aforementioned PPC platform where one entry in the returned array can describe multiple cores. qemuDomainFilterHotplugVcpuEntities is the code that cross-references the libvirt "index" with the data returned by query-hotpluggable cpus. The important bit is the 'vcpus-count' property. The code which deals with hotplug is already fetching everything that's needed.