Docs: improve Nova documentation

Adds a top-level guide for Nova, with links off to the various virt
driver guides.

Generalises the libvirt TLS guide into a libvirt guide, and adds info on
hardware virtualisation and qemu vs. kvm.

Adds information on configuring consoles.

Change-Id: I36beaaee313bdbc4bcf8cc15c41dda245a5a81ba

doc/source/reference/compute/index.rst

@@ -9,9 +9,10 @@ compute services like HyperV, XenServer and so on.
    :maxdepth: 1
 
    hyperv-guide
-   libvirt-tls-guide
+   libvirt-guide
    masakari-guide
    nova-fake-driver
+   nova-guide
    qinling-guide
    vmware-guide
    xenserver-guide

doc/source/reference/compute/libvirt-guide.rst

@@ -1,6 +1,28 @@
 .. libvirt-tls-guide:
 
-===========
+====================================
+Libvirt - Nova Virtualisation Driver
+====================================
+
+Overview
+========
+
+Libvirt is the most commonly used virtualisation driver in OpenStack. It uses
+libvirt, backed by QEMU and when available, KVM. Libvirt is executed in the
+``nova_libvirt`` container.
+
+Hardware Virtualisation
+=======================
+
+Two values are supported for ``nova_compute_virt_type`` with libvirt -
+``kvm`` and ``qemu``, with ``kvm`` being the default.
+
+For optimal performance, ``kvm`` is preferable, since many aspects of
+virtualisation can be offloaded to hardware.  If it is not possible to enable
+hardware virtualisation (e.g. Virtualisation Technology (VT) BIOS configuration
+on Intel systems), ``qemu`` may be used to provide less performant
+software-emulated virtualisation.
+
 Libvirt TLS
 ===========
 

doc/source/reference/compute/nova-guide.rst

@@ -0,0 +1,61 @@
+======================
+Nova - Compute Service
+======================
+
+Nova is a core service in OpenStack, and provides compute services. Typically
+this is via Virtual Machines (VMs), but may also be via bare metal servers if
+Nova is coupled with Ironic.
+
+Nova is enabled by default, but may be disabled by setting ``enable_nova`` to
+``no`` in ``globals.yml``.
+
+Virtualisation Drivers
+======================
+
+The virtualisation driver may be selected via ``nova_compute_virt_type`` in
+``globals.yml``. Supported options are ``qemu``, ``kvm``, ``vmware``, and
+``xenapi``. The default is ``kvm``.
+
+HyperV
+------
+
+Information on using Nova with HyperV can be found in :doc:`hyperv-guide`.
+
+Libvirt
+-------
+
+Information on the libvirt-based drivers ``kvm`` and ``qemu`` can be found in
+:doc:`libvirt-guide`.
+
+VMware
+------
+
+Information on the VMware-based driver ``vmware`` can be found in
+:doc:`vmware-guide`.
+
+XenServer
+---------
+
+Information on the XenServer-based driver ``xenapi`` can be found in
+:doc:`xenserver-guide`.
+
+Bare Metal
+----------
+
+Information on using Nova with Ironic to deploy compute instances to bare metal
+can be found in :doc:`../bare-metal/ironic-guide`.
+
+Fake Driver
+-----------
+
+The fake driver can be used for testing Nova's scaling properties without
+requiring access to a large amount of hardware resources. It is covered in
+:doc:`nova-fake-driver`.
+
+Consoles
+========
+
+The console driver may be selected via ``nova_console`` in ``globals.yml``.
+Valid options are ``none``, ``novnc``, ``spice``, or ``rdp``. Additionally,
+serial console support can be enabled by setting
+``enable_nova_serialconsole_proxy`` to ``yes``.

doc/source/reference/compute/vmware-guide.rst

@@ -1,8 +1,8 @@
 .. _vmware-guide:
 
-======
-VMware
-======
+===================================
+VMware - Nova Virtualisation Driver
+===================================
 
 Overview
 ~~~~~~~~

doc/source/reference/compute/xenserver-guide.rst

@@ -1,8 +1,8 @@
 .. _XenServer-guide:
 
-=========
-XenServer
-=========
+======================================
+XenServer - Nova Virtualisation Driver
+======================================
 
 Overview
 ========