Custom kvm -smp argument

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pabloo

New Member
Nov 4, 2020
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Hello,

Is it possible to customise how Proxmox generates the kvm -smp argument for CPU configuration?

I'm running Proxmox 6.2-15 on a 6-core 2018 Mac Mini and I'm and trying to use all 12 available threads on a macOS Catalina VM.

macOS has some limitations on CPU configurations and non-supported configurations won't boot. I can boot with 1-cpu/8-cores, but it won't boot if I select 12-cores. I have a similar problem on a 2x6-core 2010 MacPro in which 16-cores will work but 24 won't.

qm showcmd ID shows -smp '12,sockets=1,cores=12,maxcpus=12' when I select 12 cores and macOS does not boot, but if I manually run the command replacing -smp with -smp '12,cores=1' macOS does boots and it recognises all CPUs.

I tried most permutations from the CPU configuration UI but I could not get it to generate the required -smp parameter.
Is there any way I can customise it? I also tried adding it to args: in the VM .conf file but it does not work due to the other CPU configs. If I remove the CPU config from the .conf Proxmox still generates -smp with 1 core.

Thank you!
 
hi,

just set the cpulimit option in the GUI: VM -> Hardware -> Processor -> Advanced -> cpu limit

for example setting it to 1, reboot the VM and use showcmd to check you'll see it being set -smp 1
 
If I set cpulimit to 12 and cores to 1 I get -smp '1,sockets=1,cores=1,maxcpus=1'
If I set cpulimit to 12 and cores to 12 I get -smp '12,sockets=1,cores=12,maxcpus=12'

What I actually need is -smp '12,cores=1' (not sure what this macOS limitation is about).
I haven't tested it but probably adding sockets=1,maxcpus=12 will also work.

I'm okay if this can't be set from the UI, but maybe there's some .conf option I could use to make it persistent? If I could prevent Proxmox from adding -smp when cores: and sockets: is missing then I could add it to args:.

Thanks oguz, I know this is probably not a supported use case.
 
can you send the output of the full command line and your vm config?

qm config VMID and qm showcmd VMID. also pveversion -v could help.
 
Yes, thank you.

qm config 100 (with working 8-core config)
Code: 
args: -device isa-applesmc,osk="redacted" -smbios type=2 -cpu Penryn,kvm=on,vendor=GenuineIntel,+kvm_pv_unhalt,+kvm_pv_eoi,+invtsc,vmware-cpuid-freq=on,+pcid,+ssse3,+sse4.2,+popcnt,+avx,+aes,+xsave,+xsaveopt,check -device usb-kbd,bus=ehci.0,port=2
balloon: 0
bios: ovmf
boot: cdn
bootdisk: sata0
cores: 8
cpu: Penryn
efidisk0: local-lvm-nvme:vm-100-disk-0,size=4M
machine: q35
memory: 28672
name: catalina
net0: vmxnet3=62:C0:85:EB:D3:A7,bridge=vmbr0,firewall=1
numa: 0
onboot: 1
ostype: other
sata0: local-lvm-nvme:vm-100-disk-1,cache=unsafe,discard=on,size=400G,ssd=1
scsihw: virtio-scsi-pci
smbios1: uuid=aa5d96ac-a111-43ec-b3e9-dcd4d509baa6
sockets: 1
vga: vmware
vmgenid: d2132395-ac66-4409-a813-4b489e6b66ac

qm showcmd 100
/usr/bin/kvm -id 100 -name catalina -chardev 'socket,id=qmp,path=/var/run/qemu-server/100.qmp,server,nowait' -mon 'chardev=qmp,mode=control' -chardev 'socket,id=qmp-event,path=/var/run/qmeventd.sock,reconnect=5' -mon 'chardev=qmp-event,mode=control' -pidfile /var/run/qemu-server/100.pid -daemonize -smbios 'type=1,uuid=aa5d96ac-a111-43ec-b3e9-dcd4d509baa6' -drive 'if=pflash,unit=0,format=raw,readonly,file=/usr/share/pve-edk2-firmware//OVMF_CODE.fd' -drive 'if=pflash,unit=1,format=raw,id=drive-efidisk0,size=131072,file=/dev/vmdata/vm-100-disk-0' -smp '8,sockets=1,cores=8,maxcpus=8' -nodefaults -boot 'menu=on,strict=on,reboot-timeout=1000,splash=/usr/share/qemu-server/bootsplash.jpg' -vnc unix:/var/run/qemu-server/100.vnc,password -cpu 'Penryn,enforce,+kvm_pv_eoi,+kvm_pv_unhalt,vendor=GenuineIntel' -m 28672 -readconfig /usr/share/qemu-server/pve-q35-4.0.cfg -device 'vmgenid,guid=d2132395-ac66-4409-a813-4b489e6b66ac' -device 'usb-tablet,id=tablet,bus=ehci.0,port=1' -device 'vmware-svga,id=vga,bus=pcie.0,addr=0x1' -iscsi 'initiator-name=iqn.1993-08.org.debian:01:f1ae8612507a' -device 'ahci,id=ahci0,multifunction=on,bus=pci.0,addr=0x7' -drive 'file=/dev/vmdata/vm-100-disk-1,if=none,id=drive-sata0,cache=unsafe,discard=on,format=raw,aio=threads,detect-zeroes=unmap' -device 'ide-hd,bus=ahci0.0,drive=drive-sata0,id=sata0,rotation_rate=1,bootindex=100' -netdev 'type=tap,id=net0,ifname=tap100i0,script=/var/lib/qemu-server/pve-bridge,downscript=/var/lib/qemu-server/pve-bridgedown' -device 'vmxnet3,mac=62:C0:85:EB:D3:A7,netdev=net0,bus=pci.0,addr=0x12,id=net0,bootindex=300' -machine 'type=q35+pve0' -device 'isa-applesmc,osk=redacted' -smbios 'type=2' -cpu 'Penryn,kvm=on,vendor=GenuineIntel,+kvm_pv_unhalt,+kvm_pv_eoi,+invtsc,vmware-cpuid-freq=on,+pcid,+ssse3,+sse4.2,+popcnt,+avx,+aes,+xsave,+xsaveopt,check' -device 'usb-kbd,bus=ehci.0,port=2'

pveversion -v
Code: 
proxmox-ve: 6.2-2 (running kernel: 5.4.65-1-pve)
pve-manager: 6.2-15 (running version: 6.2-15/48bd51b6)
pve-kernel-5.4: 6.2-7
pve-kernel-helper: 6.2-7
pve-kernel-5.4.65-1-pve: 5.4.65-1
pve-kernel-5.4.34-1-pve: 5.4.34-2
ceph-fuse: 12.2.11+dfsg1-2.1+b1
corosync: 3.0.4-pve1
criu: 3.11-3
glusterfs-client: 5.5-3
ifupdown: 0.8.35+pve1
ksm-control-daemon: 1.3-1
libjs-extjs: 6.0.1-10
libknet1: 1.16-pve1
libproxmox-acme-perl: 1.0.5
libpve-access-control: 6.1-3
libpve-apiclient-perl: 3.0-3
libpve-common-perl: 6.2-2
libpve-guest-common-perl: 3.1-3
libpve-http-server-perl: 3.0-6
libpve-storage-perl: 6.2-9
libqb0: 1.0.5-1
libspice-server1: 0.14.2-4~pve6+1
lvm2: 2.03.02-pve4
lxc-pve: 4.0.3-1
lxcfs: 4.0.3-pve3
novnc-pve: 1.1.0-1
proxmox-backup-client: 0.9.4-1
proxmox-mini-journalreader: 1.1-1
proxmox-widget-toolkit: 2.3-6
pve-cluster: 6.2-1
pve-container: 3.2-2
pve-docs: 6.2-6
pve-edk2-firmware: 2.202002-1
pve-firewall: 4.1-3
pve-firmware: 3.1-3
pve-ha-manager: 3.1-1
pve-i18n: 2.2-2
pve-qemu-kvm: 5.1.0-4
pve-xtermjs: 4.7.0-2
qemu-server: 6.2-18
smartmontools: 7.1-pve2
spiceterm: 3.1-1
vncterm: 1.6-2
zfsutils-linux: 0.8.4-pve2
 
thanks.
you can take a look here[0] to make it easier to pass the cpu flags.

and then adding smp through that or args: could work.

you could also experiment with the available options in the cpu settings, like vCPU and socket/core count.

[0]: https://pve.proxmox.com/wiki/Manual:_cpu-models.conf
 
Thanks, I read the manual but I couldn't figure out how smp could be added to a custom CPU model.

I also tried adding smp to args: but then the command line gets two -smp arguments and depending on what I select from the UI I get different errors starting the VM:
  1. Selecting 1 core from the UI.
    kvm ... -smp '1,sockets=1,cores=1,maxcpus=1' ... -smp '12,cores=1'
    kvm: maxcpus must be equal to or greater than smp
  2. Selecting 12 cores from the UI
    kvm ... -smp '12,sockets=1,cores=12,maxcpus=12' ... -smp '12,cores=1'
    macOS doesn't boot
 
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Reactions: xrr
Confirming what pabloo ran into, trying to set smp args will result in a first smp argument coming from proxmox vm settings (core, sockets, virtual cpu as reflected by UI) and then last arg will be the "custom" -smp argument as passed by "sudo qm set 100 --args '-smp 1,sockets=2,cores=16,threads=2,maxcpus=64" or alike...

I failed trying to allow my vms to see the 32 core x 2 threads instead of 64 "plain" cores;
 
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