[Qemu-devel] [Bug 1800401] Re: efifb on Linux guest fails to load when using VGA passthrough

[Nicholas Vinson]

** Attachment added: "Gentoo.sh -- systemrescuecd-x86-5.3.1 -- dmesg.log"
   
https://bugs.launchpad.net/qemu/+bug/1800401/+attachment/5206600/+files/Gentoo.sh%20--%20systemrescuecd-x86-5.3.1%20--%20dmesg.log

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https://bugs.launchpad.net/bugs/1800401

Title:
  efifb on Linux guest fails to load when using VGA passthrough

Status in QEMU:
  New

Bug description:
  The EFI framebuffer fails to load when booting a Gentoo guest using
  ovmf + vga_passthrough.  I retested using they system rescue CD and
  saw the same issue, but also noticed that when a second framebuffer
  loads, nouveaufb in my case, the terminal appears.  I have also
  verified that the Gentoo min CD is not hanging at boot as I can type
  'poweroff' after waiting a few minutes and the system responds by
  powering off.  I am unable to reproduce with seabios as I have been
  unable to get vga passthrough to work with that BIOS.

  Steps to Reproduce:
      1. Install qemu and ovmf
      2. Download systemrescuecd-x86-5.3.1.iso
      3. Run qemu using one of the configurations below
      4. Select first boot option in GRUB menu
      5. Wait 30 seconds
      6. Press enter # System rescue is prompting for the keymap between steps 
5 and 6
      7. Wait 2 minutes
      8. Observe fb console
      9. Note lack of output until very late in boot process
     10. Check dmesg
     11. Note efifb failed to load (invalid address)
     12. Note nouveaufb started late in boot process 

  Expected Results:
     The EFI FB to load and display output to monitor.  This is the behavior I 
see when booting the host system via UEFI.

  Actual Results:
     The EFI FB fails to load and display output.  System fails to display any 
output until nouveaufb loads.  When booting using the Gentoo minCD, this makes 
the system largely unusable.

  Additional information:

  Tested using Gentoo's app-emulation/qemu-3.0.0 version.  Bug report:
  https://bugs.gentoo.org/669880

  I also tested qemu at git commit
  179f9ac887973c818b2578bd79fa3ed2522657d4.  Configuration log for the
  build will be attached.

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