My Oracle Support Banner

Oracle Linux: Hot Adding vCPU to KVM Guest Causes TSC Instability and Time Drift in Guest (Doc ID 2898384.1)

Last updated on MARCH 13, 2023

Applies to:

Linux OS - Version Oracle Linux 7.2 with Unbreakable Enterprise Kernel [4.1.12] to Oracle Linux 7.9 [Release OL7U2 to OL7U9]
Oracle Cloud Infrastructure - Version N/A to N/A [Release 1.0]
Linux x86-64


An Oracle Linux (OL) system running as a KVM host manages multiple OL7 KVM guest virtual machines running UEKR4 (4.1.12) and UEKR5 (4.14.35) kernel versions.

An additional virtual CPU (vCPU) is dynamically added (hotplugged) to an OL KVM guest.
Immediately following the addition of the vCPU, the guest reports system clock/timing instability-related messages, as well as forward or backward time drift e.g.:

Above, the KVM guest experiences a time regression from 81516.819061 to 81516.278624. 


To view full details, sign in with your My Oracle Support account.

Don't have a My Oracle Support account? Click to get started!

In this Document

My Oracle Support provides customers with access to over a million knowledge articles and a vibrant support community of peers and Oracle experts.