CPU hotplug does not work.

sand-max

Renowned Member
Apr 13, 2016
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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

Selection_137.png

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