CPU hotplug does not work.

[sand-max]

Hi guys!

version env 6.1-7


I faced with problem hotplug CPU.
I did as described here https://pve.proxmox.com/wiki/Hotplug_(qemu_disk,nic,cpu,memory).

root@template-deb10:~# modprobe acpiphp
modprobe: FATAL: Module acpiphp not found in directory /lib/modules/4.19.0-6-amd64

root@template-deb10:~# modprobe pci_hotplug
modprobe: FATAL: Module pci_hotplug not found in directory /lib/modules/4.19.0-6-amd64

But looks like modules loaded

root@template-deb10:~# grep "CONFIG_HOTPLUG_PCI_ACPI=" /boot/config-`uname -r`
CONFIG_HOTPLUG_PCI_ACPI=y

root@template-deb10:~# grep "CONFIG_HOTPLUG_PCI=" /boot/config-`uname -r`
CONFIG_HOTPLUG_PCI=y

root@template-deb10:~# grep "CONFIG_HOTPLUG_CPU=" /boot/config-`uname -r`
CONFIG_HOTPLUG_CPU=y

root@template-deb10:~# grep "CONFIG_MEMORY_HOTPLUG=" /boot/config-`uname -r`
CONFIG_MEMORY_HOTPLUG=y

Added to grub "memhp_default_state=online"

root@template-deb10:~# cat /boot/grub/grub.cfg | grep online
linux /vmlinuz-4.19.0-6-amd64 root=/dev/mapper/vg01--root-lv01--root ro quiet memhp_default_state=online
linux /vmlinuz-4.19.0-6-amd64 root=/dev/mapper/vg01--root-lv01--root ro quiet memhp_default_state=online

But it does not work for CPU without reboot guest VM. For adding hotpug memory it works OK!

 

[spirit]

you can't change socket or cores online, but you can changes "vcpus" value. (in the advanced section when you edit processors)

vcpus = current online cores

sockets*cores = the max vcpus you can hotplug.