What's the future of Xen in mainline?

What's the future of Xen in mainline?

I used kvm on an Opteron server running Ubuntu Gutsy with 2 virtual machines for about 3 months with no problems, but when I added a 3rd VM, the kernel began to panic with an unhandled page fault on an almost daily basis. The panics appeared to coincide with heavy CPU load on the 3rd VM. I tried the latest vanilla kernel (2.6.24 at the time, I think) but got the same results as with the Ubuntu 2.6.22 kernel. I switched to the Ubuntu Xen kernel, rebuilt all my VMs as Xen domU's, and the machine has been up ever since, happily running 4 domU's now.

Regardless of any kernel bugs, the free software tools people have built around Xen (e.g., xen-tools) and the fantastic xm command made it worth the switch. kvm's choice of QEMU as a platform hampers its use on servers. QEMU appears to target the desktop virtualization crowd, which is fine, of course, but it's not well-suited for remote/headless work. I could never get the serial consoles on my kvm guests to work reliably, and I had to use GNU screen to manage the guests, since QEMU doesn't include the ability to attach/detach a session as xm does. The libvirt project may resolve this in time, but currently it doesn't work particularly well with QEMU, in my experience; for example, I couldn't get the serial console to work at all with virsh and friends.

My main concern with Xen is its future. Debian and Fedora appear to have frozen upstream integration while Xen is ported to paravirt-ops, which sounds like the right move given Citrix's acquisition of XenSource, but does anyone here know how that work is going, and when we'll be able to build Xen kernels from the mainline Linux kernel?

Indeed we've not hooked up the text based serial console in QEMU to 'virsh console' yet. It
has long been on the TODO list, but never quite made it to the top... VNC is the most common
access method for graphical console, or just SSH into the guest for text mode.

My sister runs an internet cafe , for her i had put up zersohell and ipcop using qemu on a
single machine . That machine is without monitor , she only need to switch on the machine and
can follow the status of vm's remotely using vnc (only if required) and can manage zeroshell
and ipcop through web interface. Good thing about qemu is that it can use linux native network
tools like bridge-utils , this way one can create sophisticated virtual network environment
using qemu. 

I run a modest number of OpenVZ kernels with some couple dozen VPS on all of them (half of
these runs on one dualcore, 4Gb system).  Just works, and handles added load quite well.

It's ALT Linux 4.0 Server (which integrates OpenVZ support out-of-box).

You can get updates on the progress of the Xen paravirt ops work on the Fedora wiki, since
we're targetting Fedora 9:

http://fedoraproject.org/wiki/Features/XenPvops

And frequent postings to the xen-devel mailing list

http://lists.xensource.com/archives/html/xen-devel/2008-0...

Short summary,  i386, Dom0 and DomU both work on pvops + 2.6.24 and we can spawn guests.
x86_64 DomU is very close to being usable. 

Stephen publishes his GIT repo with the work

http://git.et.redhat.com/?p=linux-2.6-dom0-pvops.git;a=su...