[fedora-virt] F12 feature: Host information

Richard W.M. Jones rjones at redhat.com
Tue Jun 16 10:34:12 UTC 2009

I posted this page on the wiki last week, which is a feature we intend
to implement for Fedora 12:


Any comments?


  "Allow a virtual machine to see information and statistics from the
  host operating system, under narrow and strictly controlled conditions
  and only at the discretion of the host administrator.

  Detailed Description

  Allow a virtual machine to look at host information (such as number of
  physical, not just virtual CPUs), and statistics like the load on the
  host. Users have asked for this primarily as a diagnostic tool -- for
  example, poor performance of a virtual machine might be caused by
  excessive load on the host.

  Normally we try to isolate virtual machines from accessing any such
  details from the host, and there are very good reasons for that too,
  such as security of the host, commercial confidentiality, and the
  privacy of other virtual machines running on the host. As a result, at
  the moment there is no mechanism for accessing host information.

  We propose to add a feature which allows the host administrator, at
  their discretion, and only of limited data to limited virtual
  machines, to export host information and statistics to virtual

  Administrators will need to:

    * explicitly enable this feature,
    * select the virtual machines and/or data they wish to be seen in guests,
    * select the frequency that guests can ask for data. 

  The mechanism will be a daemon running on the host which collects the
  statistics (see below for what). The information will be exported to
  guests over a spare (virtual) serial port or through the qemu/kvm
  vmchannel feature, whichever is available.

  Guests will request information by sending a plain text command to the
  serial port, and will receive information in the form of a simple,
  plain text message. No special drivers or software are required by the

Richard Jones, Emerging Technologies, Red Hat  http://et.redhat.com/~rjones
New in Fedora 11: Fedora Windows cross-compiler. Compile Windows
programs, test, and build Windows installers. Over 70 libraries supprt'd
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