Re: [Xen-users] PV DomU VNC screen black and Xorg error

[Paul Schulze <avlex@xxxxxxx>]

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Am 15.06.2008 um 16:30 schrieb jim burns:

> See if this helps. Below is my xorg.conf from my F9 pv domu. In  
> particular, I
> would try adding to your config:
>
> In your 'Section "ServerLayout"', I would change InputDevice to  
> include the
> keyboard - 'InputDevice  "Xen Mouse" "Generic Keyboard"'.
>
> In your 'Section "Screen"', I would remove the Monitor line, and  
> add something
> like my DefaultDepth and 'SubSection "Display"' lines.
>
> Good luck!
Hi again,

Thanks Jim for trying to help me, but the solution for the problem  
wasn't all that easy. And yeah, this means I solved the mystery:
The culprit is xserver-xorg-core in Ubuntu Hardy, which according to  
an OpenSuse 10.3 bug report (https://bugzilla.novell.com/show_bug.cgi? 
id=285523) doesn't support the pixclock value (whatever that is) set  
by the Xen framebuffer. I originally dismissed the idea of this being  
relevant, since the problem was known for quiet a while there and I  
thought since it was solved about a year ago, the patch should have  
made its way into the Xorg 7.3 tree already or at least adapted by  
Ubuntu (I'll have to contact the package maintainer about that  
later), but it turns out, that the solution of OpenSuse was dead on.  
This also means that the same bug might or might not be present in  
other distributions that use Xorg 7.3 too.
Here is what I did (for everyone who is interested):

1) Installing the build dependancies and getting the xserver-xorg- 
core sources for a rebuild:
sudo apt-get build-dep xserver-xorg-core
apt-get source xserver-xorg-core


2) Creating the patch file (this is a recreation of the OpenSuse 10.3  
patch, adjusted for use with the debian build tools)
cd xserver-xorg-<Hit TAB>
cat << EOF > debian/patches/999_xen_pvfb_pixclock.patch
diff -Naur xorg-server-1.4.1~git20080131.orig/hw/xfree86/fbdevhw/ 
fbdevhw.c xorg-server-1.4.1~git20080131/hw/xfree86/fbdevhw/fbdevhw.c
- --- xorg-server-1.4.1~git20080131.orig/hw/xfree86/fbdevhw/ 
fbdevhw.c     2008-06-15 21:18:54.000000000 +0200
+++ xorg-server-1.4.1~git20080131/hw/xfree86/fbdevhw/fbdevhw.c   
2008-06-15 21:19:56.000000000 +0200
@@ -245,7 +245,7 @@
                set->green.length == req->green.length &&
                set->blue.length == req->blue.length &&
                set->xres == req->xres && set->yres == req->yres &&
- -               set->pixclock == req->pixclock &&
+               ((set->pixclock == req->pixclock) || !set->pixclock) &&
                set->right_margin == req->right_margin &&
                set->hsync_len == req->hsync_len &&
                set->left_margin == req->left_margin &&
EOF

And adding it to the list of patches that are used to build the package:
echo "999_xen_pvfb_pixclock.patch" >> debian/patches/series


3) Editing the changelog, so my version overwrites the current  
version of the package, but is overwritten if a new version of the  
package comes out, and I can or rather have to update the package. I  
added the following lines to the beginning of debian/changelog in the  
current directory:
- --- debian/changelog ---
xorg-server (2:1.4.1~git20080131-1ubuntu9.2.1) hardy-security;  
urgency=low
  * Fix Xen PV guest issue:
    + 999_xen_pvfb_pixclock.patch

 -- My Name <my@xxxxxxxxxxxx>  Sun, DOM MON YEAR HH:MM:SS TZ
- ---

You'll have to adjust the last line, so it fits your name, mail  
address and time (I'm sure there's a tool to create a basic entry  
automatically, but I just use copy/paste anyways, so same  
difference). If you don't want to have to build the package every  
time it is updated by Ubuntu, you will have to pin it, but since  
X.org is regularly subject to security updates and a basic package  
for every desktop that many others depend on, I don't recommend it.

4) Building the package (the most simple thing ever, it just takes  
alot of time):
debuild


5) Installing it:

dpkg -i ../xserver-xorg-core-<Hit TAB>


This solution did the trick for me in terms of Xorg starting up, but  
when I open the VNC window, provided by Xen, the colors are all  
screwed up and the mouse acts funky. So for an initial setup, this is  
ok, but I've decided to rather use Vino from there after all. Though  
I hope this will help at least some people.
Cheers,


Paul.

- --
Paul Schulze
avlex@xxxxxxx
Public Key: http://solaris-net.dyndns.org/keys/key_avlex.asc

"Making mistakes is human,
but to really fuck things up you need Computers"
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