Created attachment 678246 [details]
Blank screen with green pattern after console switch

Description of problem:
After starting X in a Xen VM, switching to a text console with Ctrl-Alt-Fx results in a black or garbled screen. No text console login is possible

Version-Release number of selected component (if applicable):
grub2-2.00-13.fc18.x86_64
kernel-3.6.10-4.fc18.x86_64
package xorg-x11-server is not installed
xorg-x11-drv-vesa-2.3.2-2.fc18.x86_64

How reproducible:
always

Steps to Reproduce:
1. Install F18 on Xen VM (SUSE SLES11 SP2 xen 4.1.3_06-0.7.1, qemu-dm 0.10.2)
2. Send Ctrl-Alt-F2
  
Actual results:
Blank screen, sometimes with strange patterns

Expected results:
Text console login possible

Additional info:

1. Switching back to X works,, only the text console is affected.

2. The same problem occurs also if "gfxpayload=text" is set in grub.cfg (although the screen looks a bit different in this case - a cursor can be seen in this mode but no text).

3. This happens only with the VESA driver (which is default in F18 for VMs). By forcing Xorg to use the FBDEV driver using xorg.conf, the problem can be avoided (but without hacking grub2 configuration, the screen resolution is limited to lousy 800x600).

When the system is booted into runlevel 3, the text console is OK at first, but after starting X/vesa in any way, it isn't usable any more.

The same thing happens with F17, too. RHEL6 VMs do not show the same problem, nor do other older Linux VMs.

This is the xen domu configuration:
<domain type='xen'>
  <name>F18</name>
  <uuid>1c45379f-8bbf-bec4-5677-42211d3430d1</uuid>
  <description>F18 test VM</description>
  <memory>2097152</memory>
  <currentMemory>2097152</currentMemory>
  <vcpu>1</vcpu>
  <os>
    <type>hvm</type>
    <loader>/usr/lib/xen/boot/hvmloader</loader>
    <boot dev='hd'/>
  </os>
  <features>
    <acpi/>
    <apic/>
    <pae/>
    <hap/>
  </features>
  <clock offset='utc'>
    <timer name='hpet' present='no'/>
  </clock>
  <on_poweroff>destroy</on_poweroff>
  <on_reboot>restart</on_reboot>
  <on_crash>destroy</on_crash>
  <devices>
    <emulator>/usr/lib/xen/bin/qemu-dm</emulator>
    <disk type='file' device='disk'>
      <driver name='file'/>
      <source file='/var/lib/libvirt/images/f18.img'/>
      <target dev='hda' bus='ide'/>
    </disk>
    <interface type='bridge'>
      <mac address='00:16:3e:08:bc:64'/>
      <source bridge='br1'/>
      <script path='/etc/xen/scripts/vif-bridge'/>
    </interface>
    <serial type='pty'>
      <target port='0'/>
    </serial>
    <console type='pty'>
      <target type='serial' port='0'/>
    </console>
    <input type='mouse' bus='usb'/>
    <input type='mouse' bus='ps2'/>
    <graphics type='vnc' port='-1' autoport='yes' keymap='de'/>
  </devices>
</domain>