[config-ref] Convert compute QEMU to RST

Change-Id: I9cb8e6179474287198e13986bdf0b1e049e0a6a8
Implements: blueprint config-ref-rst

doc/config-ref-rst/source/compute/hypervisor-qemu.rst

@@ -1,3 +1,54 @@
 ====
 QEMU
 ====
+
+From the perspective of the Compute service, the QEMU hypervisor is
+very similar to the KVM hypervisor. Both are controlled through libvirt,
+both support the same feature set, and all virtual machine images that
+are compatible with KVM are also compatible with QEMU.
+The main difference is that QEMU does not support native virtualization.
+Consequently, QEMU has worse performance than KVM and is a poor choice
+for a production deployment.
+
+The typical uses cases for QEMU are
+
+* Running on older hardware that lacks virtualization support.
+* Running the Compute service inside of a virtual machine for
+  development or testing purposes, where the hypervisor does not
+  support native virtualization for guests.
+
+To enable QEMU, add these settings to ``nova.conf``:
+
+.. code-block:: ini
+
+   compute_driver = libvirt.LibvirtDriver
+
+   [libvirt]
+   virt_type = qemu
+
+For some operations you may also have to install the
+:command:`guestmount` utility:
+
+On Ubuntu:
+
+.. code-block:: console
+
+   # apt-get install guestmount
+
+On Red Hat Enterprise Linux, Fedora, or CentOS:
+
+.. code-block:: console
+
+   # yum install libguestfs-tools
+
+On openSUSE:
+
+.. code-block:: console
+
+   # zypper install guestfs-tools
+
+The QEMU hypervisor supports the following virtual machine image formats:
+
+* Raw
+* QEMU Copy-on-write (qcow2)
+* VMware virtual machine disk format (vmdk)