Communication From xVM Hypervisor to Dom0 Using xm

Although the hypervisor and dom0 work closely together to manage a running system, the dom0 operating system has little direct visibility into the hypervisor. The hypervisor's entire address space is inaccessible to the dom0.

The only source of information is provided by the xm command, a user-space tool that communicates with the hypervisor via hypercalls.

Some of the commonly used xm commands are:

xm info

Report static information about the machine, such as number of CPUs, total memory, and xVM version.

# xm info
host                   : test
release                : 5.11
version                : onnv-userj
machine                : i86pc
nr_cpus                : 2
nr_nodes               : 1
sockets_per_node       : 2
cores_per_socket       : 1
threads_per_core       : 1
cpu_mhz                : 2391
hw_caps                : 078bfbff:e1d3fbff:00000000:00000010
total_memory           : 4031
free_memory            : 1953
xen_major              : 3
xen_minor              : 1
xen_extra              : .2-xvm
xen_caps               : xen-3.0-x86_64 xen-3.0-x86_32p
xen_scheduler          : credit
xen_pagesize           : 4096
platform_params        : virt_start=0xffff800000000000
xen_changeset          : Thu Dec 20 20:11:49 2007 -0800 15623:41d827ccece7
cc_compiler            : gcc version 3.4.3 (csl-sol210-3_4-20050802)
cc_compile_by          : userj
cc_compile_domain      : lab.sun.com
cc_compile_date        : Thu Dec 20 20:24:36 PST 2007
xend_config_format     : 4

xm list

List all domains and some high-level information.

xm top

Analogous to the Linux top command, but it reports domain information instead of process information. Information about the xVM system and domains is displayed in a continuously updating manner through the xentop command. See xentop.

xm log

Display the contents of the xend log.

xm help

List all the available commands.

xentrace

Capture trace buffer data from xVM.

xentop

Display information about the xVM system and domains in a continuously updating manner. See xm top.

xm start domain

Start a managed domain that was created by virt-install.

If you modify guest domain CPUs or memory by using the xm command, these changes will be saved in the configuration file and persist across reboots.

See the xm(1M) man page for more information.