Some Linux guests may cause a high CPU load even if the guest system appears to be idle. This can be caused by a high timer frequency of the guest kernel. Some Linux distributions, for example Fedora, ship a Linux kernel configured for a timer frequency of 1000Hz. We recommend to recompile the guest kernel and to select a timer frequency of 100Hz.

Most Linux-based guests will fail with AMD Phenoms or Barcelona-level Opterons due to a bug in the Linux kernel. Enable the I/O-APIC to work around the problem (see Sectioná3.7.1.2, “"Advanced" tab”).