The guest OS does not display the vCPUs added using hotplug

emptness

Member
Aug 19, 2022
100
6
18
Hello everyone!
I'm testing adding a cpu without restarting the VM.
The guest OS does not display the added vCPUs.
What could be the matter? Is this a bug?

1699016147100.png
1699016176990.png
 
The processor cannot be changed at runtime. You would have to restart the VM to apply the changes.
 
Aren't these rules created automatically when installing qemu-guest-agent?
I have not experienced that and I don't know why you would expect that from the Wiki page.
OS Ubuntu 20.04
I needed to add it myself for Ubuntu with qemu-guest-agents installed and active. Which kernel modules and parameters and/or udev rules are necessary (inside the VM) depend on the exact kernel version inside your Ubuntu VM.
VM options are configured for hotplug.
View attachment 57521
Maybe sure to enable everything necessary inside the VM for automatic memory hotplug, otherwise the VM sees only 1GB of memory (or less)!
 
Last edited:
I have not experienced that and I don't know why you would expect that from the Wiki page.

I needed to add it myself for Ubuntu with qemu-guest-agents installed and active. Which kernel modules and parameters and/or udev rules are necessary (inside the VM) depend on the exact kernel version inside your Ubuntu VM.

Maybe sure to enable everything necessary inside the VM for automatic memory hotplug, otherwise the VM sees only 1GB of memory (or less)!
Thank you for your advice.
The rule SUBSYSTEM=="cpu", ACTION=="add", TEST=="online", ATTR{online}=="0", ATTR{online}="1" helped. Now the number of processors is changing inside the VM.
By the way, RAM expands without problems. No additional actions were required inside the VM.
 

About

The Proxmox community has been around for many years and offers help and support for Proxmox VE, Proxmox Backup Server, and Proxmox Mail Gateway.
We think our community is one of the best thanks to people like you!

Get your subscription!

The Proxmox team works very hard to make sure you are running the best software and getting stable updates and security enhancements, as well as quick enterprise support. Tens of thousands of happy customers have a Proxmox subscription. Get yours easily in our online shop.

Buy now!