XEN: Unable to install fully-virtual DomU

This document (7000057) is provided subject to the disclaimer at the end of this document.

Environment

SUSE Linux Enterprise Server 10 Service Pack 1

Situation

While running the Xen kernel, YaST or "virt-manager" reports that the computer is not capable of installing a fully-virtual DomU.

Resolution

A common misconception is that because the CPU supports VT that all fully-virtual DomU's are supported. If the "xm info" does not show the correct xencap for the DomU you are trying to install, then there is a hardware block. Please make sure that the physical BIOS has virtualization enabled (this may show in the BIOS as "virtualization support", "virtualization enabled", "VT Technology", etc.).

Finally, some hardware makers have a physical block on the front side bus that prevents hardware virtualization from being supported. Typically lower end servers, mid and low end workstations and consumer level hardware have this turned off and there is no way to turn it on.

The command, "xm info" will identify the type of guests that can run under Xen. The information reported by "xm info" reports the hardware's capability of running.

halo:~ # xm info
host : halo
release : 2.6.16.54-0.2.3-xen
version : #1 SMP Thu Nov 22 18:32:07 UTC 2007
machine : x86_64
nr_cpus : 4
nr_nodes : 1
sockets_per_node : 1
cores_per_socket : 1
threads_per_core : 4
cpu_mhz : 2400
hw_caps : bfebfbff:20100800:00000000:00000140:0000e3bd:00000000:00000001
total_memory : 8183
free_memory : 5219
max_free_memory : 5219
max_para_memory : 5215
max_hvm_memory : 5194
xen_major : 3
xen_minor : 0
xen_extra : .4_13138-0.60
xen_caps : xen-3.0-x86_64 xen-3.0-x86_32p hvm-3.0-x86_32 hvm-3.0-x86_32p hvm-3.0-x86_64
xen_pagesize : 4096
platform_params : virt_start=0xffff800000000000
xen_changeset : 13138
cc_compiler : gcc version 4.1.2 20070115 (prerelease) (SUSE Linux)
cc_compile_by : abuild
cc_compile_domain : suse.de
cc_compile_date : Wed Nov 28 15:42:33 UTC 2007
xend_config_format : 3

The relavent line in the output is the "xen caps"

xen_caps xen-3.0-x86_64 xen-3.0-x86_32p hvm-3.0-x86_32 hvm-3.0-x86_32p hvm-3.0-x86_64

The following table explains the meaning of the "xen caps" output and the guests that can be supported.

xencap	DomU Type
xen-3.0-x86_64	Para-virtual, 64bit
xen-3.0-x86_32p	Para-virutal, 32bit
hvm-3.0-x86_32	Fully virtual, 32bit
hvm-3.0-x86_32p	Fully virtual, running para-virtual guest, 32bit
hvm-3.0-x86_64	Fully virtual, 64bit

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