Virtualization, Servers and Storage : Hot-Add CPU not working on Ubuntu

Created by JM Lopez on Feb 04, 2024

(blue star) Problem

Although Hot added CPUs are identified and registered by the kernel, CPUs are not brought online.

(blue star) Solution

Create a udev rule to automatically enable the hot added CPU as follows.

  1. Create a new udev rule 99-vmware-cpuhotplug-udev.rules under /etc/udev/rules.d directory, then add the following line into the file:  

    # VMware CPU HotPlug automatization
# Automatically bring on-line added processors.
#
 
SUBSYSTEM=="cpu", ACTION=="add", TEST=="online", ATTR{online}=="0", ATTR{online}="1"

  2. Restart the udev: 

    systemctl restart udev

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