Bug 206147 - Xen paravirt framebuffer is mangled under firstboot
Xen paravirt framebuffer is mangled under firstboot
Status: CLOSED RAWHIDE
Product: Fedora
Classification: Fedora
Component: xen (Show other bugs)
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All Linux
medium Severity medium
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Assigned To: Xen Maintainance List
Brian Brock
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Depends On:
Blocks:
  Show dependency treegraph
 
Reported: 2006-09-12 10:37 EDT by Daniel Berrange
Modified: 2007-11-30 17:11 EST (History)
2 users (show)

See Also:
Fixed In Version:
Doc Type: Bug Fix
Doc Text:
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Clone Of:
Environment:
Last Closed: 2006-09-12 11:22:46 EDT
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CRM:
Verified Versions:
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oVirt Team: ---
RHEL 7.3 requirements from Atomic Host:


Attachments (Terms of Use)
Log file from Xorg when running under firstboot (11.16 KB, text/plain)
2006-09-12 10:37 EDT, Daniel Berrange
no flags Details
Logfile from Xorg when running (normally) under GDM (11.34 KB, text/plain)
2006-09-12 10:39 EDT, Daniel Berrange
no flags Details
Display info when running firstboot (2.98 KB, text/plain)
2006-09-12 10:40 EDT, Daniel Berrange
no flags Details
Display info when running (normally) under GDM (3.28 KB, text/plain)
2006-09-12 10:41 EDT, Daniel Berrange
no flags Details
Screenshot of mangled firstboot display (57.77 KB, image/png)
2006-09-12 10:42 EDT, Daniel Berrange
no flags Details

  None (edit)
Description Daniel Berrange 2006-09-12 10:37:18 EDT
Description of problem:
When the firstboot program starts up in a Xen paravirt guest, the framebuffer is
completely mangled. The screen is half-width & duplicated side-by-side, and has
a serious colour shift across it. 

Version-Release number of selected component (if applicable):
2.6.17-1.2630.fc6xen #1 SMP Wed Sep 6 16:40:06 EDT 2006 x86_64 x86_64 x86_64
GNU/Linux


How reproducible:
Always

Steps to Reproduce:
1. Provision a new rawhide guest
2. Attach VNC viewer to guest display at first boot after installation
3. Wait for firstboot to launch
  
Actual results:
Screen is half-size & colour shifted

Expected results:
Screen displays "normally"

Additional info:
Hacking the rhpxl sources to save Xorg logs to a file rather than /dev/null, I
managed to compare the Xorg logs to normal X startup under the Xen paravirt
framebuffer. The critical difference is:

< (**) FBDEV(0): Depth 24, (--) framebuffer bpp 32
< (==) FBDEV(0): RGB weight 888
---
> (**) FBDEV(0): Depth 16, (--) framebuffer bpp 16
> (==) FBDEV(0): RGB weight 565

So, firstboot is starting an X server in 16 bpp mode, which explains the
half-width display & the 565 rgb weight explains the colour shift.

The question is how is this even possible ? The kernel paravirt framebuffer
driver is hardcoded to 32bpp, 800x600 so there should be no way for the
firstboot Xorg server to even try  a 16bpp display - it simply isn't supported
by the virtual display driver.
Comment 1 Daniel Berrange 2006-09-12 10:37:18 EDT
Created attachment 136072 [details]
Log file from Xorg when running under firstboot
Comment 2 Daniel Berrange 2006-09-12 10:39:11 EDT
Created attachment 136073 [details]
Logfile from Xorg when running (normally) under GDM
Comment 3 Daniel Berrange 2006-09-12 10:40:16 EDT
Created attachment 136074 [details]
Display info when running firstboot
Comment 4 Daniel Berrange 2006-09-12 10:41:18 EDT
Created attachment 136076 [details]
Display info when running (normally) under GDM
Comment 5 Daniel Berrange 2006-09-12 10:42:20 EDT
Created attachment 136077 [details]
Screenshot of mangled firstboot display
Comment 6 Jeremy Katz 2006-09-12 11:22:46 EDT
Okay, firstboot fixed to use the same logic as everything else which will make
this a non-issue.

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