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SMP virtual machines running Linux using the TSC clocksource stop responding or stall

Symptoms

Guest operating system stops responding
Cannot perform actions on the guest operating system

Purpose

Clocksource is the name of the new timekeeping subsystem introduced in the Linux 2.6.18 kernel. In this subsystem there are several clocksources that can be used to read the time. One of them is the tsc clocksource which uses the Time Stamp Counter that is present on each processor and can be used to track how much time has elapsed. The TSCs on the different processors are not necessarily perfectly in sync with each other, so time can appear to go backward if the TSC is read on one processor and then another processor. Early versions of the tsc clocksource did not handle this case, which can lead to the guest operating system not responding. Due to the different timing behavior of running in a virtual machine, this can be observed more frequently in a virtual machine.

Resolution

Affected Kernels

Clocksource was introduced in 2.6.18 for 32 bit kernels and in 2.6.21 for 64 bit kernels. This issue is fixed in 2.6.26 for both 32 and 64 bit kernels. This is only an issue when using a virtual machine with more than one virtual CPU.

Affected Flavors and Versions

The following flavors/versions are affected:

Asianux 3 32 bit
CentOS 5.2 32 bit
CentOS 5.1 32 bit
CentOS 5.0 32 bit
Mandriva Linux 2008 32 bit and 64 bit
Oracle Enterprise Linux 5 32 bit
RHEL 5.2 32 bit
RHEL 5.1 32 bit
RHEL 5.0 32 bit
SUSE Linux 10.3 32 bit and 64 bit
SUSE Linux 10.2 32 bit
Ubuntu 8.04 32 bit and 64 bit
Ubuntu 7.10 32 bit and 64 bit
Ubuntu 7.04 32 bit

The issue is fixed in a patch update for RHEL 5.2. For more information, see RHSA-2008:0519 - Security Advisory at https://rhn.redhat.com/rhn/errata/details/Details.do?eid=7228.

This issue is fixed in a patch update for Centos 5.2. For more information, see CentOS Errata and Security Advisory 2008:0519 at http://lists.centos.org/pipermail/centos-announce/2008-June/015036.html.

This issue is fixed in Ubuntu 8.04.2.

This issue is fixed in Asianux 3 SP1 32bit.

Solution

The workaround for kernels with this issue is to use the acpi_pm clocksource. This can be done by putting clocksource=acpi_pm on the kernel command line.

For more information, see Linux Timekeeping Best Practices KB 1006427.

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KB Article: 1007020
Updated: Sep 11, 2009

Products:
VMware ACE
VMware ESX
VMware ESXi
VMware Fusion
VMware GSX Server
VMware Player
VMware Server
VMware Workstation

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