Re: [fedora-virt] Fedora 12 Xen guests (domU) and hosts (dom0)

[Pasi Kärkkäinen]

On Fri, Jan 15, 2010 at 01:54:09PM +0200, Pasi Kärkkäinen wrote:
>  Hello,
>  
>  I thought of writing some information about running Fedora 12 Xen guests
>  and also Fedora 12 Xen hosts/dom0.
>  
>  Fedora 12 includes the upstream Linux pv_ops Xen domU support in the default kernel.
>  By using virt-install or virt-manager you can install Fedora 12 Xen PV 
>  (paravirtual) guests directly from network, for example on RHEL 5.4, 
>  CentOS 5.4, or Fedora Xen dom0/host.
>  
>  If you want to run Fedora 12 Xen dom0 (host), there are some extra steps
>  needed. Fedora 12 ships with Xen hypervisor and management tools 
>  (Xen 3.4.1, and Xen 3.4.2 in the F12 updates), but the required Xen dom0 
>  capable host kernel is not included in Fedora atm/yet.
>  
>  General information about Xen dom0 status in Fedora: 
>  http://fedoraproject.org/wiki/Features/XenPvopsDom0
>  
>  There are a couple of different ways to get and install a Xen dom0
>  capable kernel to Fedora 12 host:
>  
>  - By using pre-packaged pv_ops xendom0 kernel rpms by M A Young. his repository:
>    http://fedorapeople.org/~myoung/dom0/
>  
>  - Compiling and installing Xen dom0 capable kernel yourself/manually.
>    
>    There are many options to choose from, full list of the available Xen
>    dom0 capable kernels is here:
>    http://wiki.xensource.com/xenwiki/XenDom0Kernels
>  
>    The recommended dom0 kernel is the pv_ops kernel, which is in the
>    process of being cleaned up for upstream/mainline Linux inclusion.
>  
>    More information about pv_ops dom0 kernel, including the status
>    reports:
>    http://wiki.xensource.com/xenwiki/XenParavirtOps
>  
>    Xen developers are interested of both the success and failure reports
>    when using the Xen pv_ops dom0 kernel.
>  
>  
>  Tips for running Xen with Fedora 12:
>  
>  	- Make sure you install all the latest Fedora 12 updates, since they
>  	  have an updated Xen version (3.4.2), and also fix a bug in
>  	  python-virtinst tool to make Xen guest console keymaps work properly:
>  	  https://bugzilla.redhat.com/show_bug.cgi?id=533707
>  
>  	- Recent versions of Xen pv_ops dom0 kernel renamed some xen
>  	  backend driver modules to have "xen-" prefix in them, for
>  	  example evtchn module became xen-evtchn. Fedora Xen 3.4.2 init
>  	  scripts take care of this, and load the correct modules, but
>  	  Xen 3.4.1 doesn't do this automatically, causing xend fail to
>  	  start in dom0/host before the modules are loaded manually.
>  
>  	- There are some upcoming apic-related changes coming in pv_ops 
>  	  dom0 kernel, which will require a patch to Xen hypervisor. 
>  	  This patch is not yet included in the Fedora Xen rpms. 
>  	  The patch will be added to Fedora Xen rpms when the upstream 
>  	  pv_ops kernel starts to require/use it.
>  
>  	- pv_ops dom0 kernel currently lacks blktap2 support, so using
>  	  tap:aio: backend disk image files is not yet possible. 
>  	  Xen file: backend image files work though. 
>  
>  	  At the moment it's recommended to use LVM volumes for guest
>  	  disks (Xen phy: backend).
>  
>  	- virt-manager seems to work OK on Fedora 12 Xen dom0.
>  	
>  	- If you experience problems related to Fedora 12 guests (domU)
>  	  kernel crashing (especially related to save/restore/migration), 
>  	  install the latest Fedora updates to the guest. There has been 
>  	  a lot of Xen guest related fixes in the upstream Linux recently. 
>  	  These fixes will appear in Fedora when the kernel gets updated 
>  	  to include the latest stable upstream fixes.
>   
Replying to myself again.. I forgot one thing from the list of tips:

	- Disable selinux from /etc/selinux/config to make it easier to
	  use custom directories for storing Xen guest image files and
	  prevent other problems from happening.


-- Pasi