[Xen-users] Re: Xen and mythbackend

[Mark Hurenkamp <mark.hurenkamp@xxxxxxxxx>]

Hi,


I'm currently running a DomU mythbackend using a PVR500, on an
old Duron 1.2Ghz machine (as described in 'CoolConfigurations'
on the Wiki).

When I started out, it was quite troublesome to get it to work
properly (mostly about finding the right kernel and xen configuration).
However, stability of both Xen and the ivtv drivers has improved
significantly since then, and I am now running Xen 3.1.3 (a test
version of a couple of months ago), with a custom build 2.6.18
kernel (as per Xen archive) for my Dom0 using Ubuntu 7.10.
In my DomU I have the Ubuntu Xen 2.6.22 kernel running with its
integrated ivtv driver, and this works really stable for me.

One very central point I came across: Memory & DMA usage.
During boot (of the physical machine), I need to make sure that
dom0 uses only about 500M or less of the available 1.8G of memory, 
or my Mythtv DomU (also 500M) would have trouble booting(kernel
panic related to loading of ivtv driver).
Also, start the Mythtv domain prior to any other domains you want 
to run.
For running Mythtv with a PVR500 (or 150/250/350) I would strongly
advice to use a kernel which has the ivtv driver integrated like
the ubuntu 2.6.22.x kernel. Older versions of the ivtv driver had
various stability issues. Make sure to use at least 0.10 or higher
if you go for an out-of-kernel ivtv driver.
(I strongly recommend Ubuntu 7.10 for mythtv domU, using its
packaged 2.6.22.x xen kernel)

Dom0 boot entry in grub (removed some unrelated stuff):

        title  Gutsy Dom0 (Xen3.1.3 2.6.18.8-xen /dev/vg0/dom0_root)
        root   (hd0,0)
        kernel /boot/xen-3.1.3.gz dom0_mem=524288
        module /boot/vmlinuz-2.6.18.8-xen 
pciback.hide=(0000:02:08.0)(0000:02:09.0) root=/dev/vg0/dom0_root ro 
console=tty1
        module /boot/initrd.img-2.6.18.8-xen

My Mythtv xen config looks like this (removed some unrelated stuff):

        bootloader = "/usr/bin/pygrub"
        memory = 500
        name = "myth"
        vif = [ 'mac=aa:00:00:00:02:07, bridge=loc' ]
        disk = [
            'phy:svr/myth_root,hda1,w',
            'phy:svr/myth_swap,hda2,w'
            ]
        pci = [
            '02:08.0',
            '02:09.0'
            ]
        root = "/dev/hda1 ro"
        extra = "swiotlb=force console=hvc0"

My Mythtv DomU grub entry looks like this:

        title           Ubuntu 7.10 kernel 2.6.22-14-xen
        root            (hd0,0)
        kernel          /boot/vmlinuz-2.6.22-14-xen console=hvc0 root=/dev/hda1 
rw swiotlb=force
        initrd          /boot/initrd.img-2.6.22-14-xen


If you have more questions, please feel free to ask!


Greetz,
Mark.


P.S.
If your Mythtv doesn't run stable without Xen, then I don't think
that running Mythtv in a Xen DomU will be more stable, especially
if the problems are hardware related.
(only thing you might achieve by using Xen is that other functions
are not taken down when your mythtv domain dies)



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