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Re: [vfio-users] Guest does not boot OS with GPU passed through, stuck at TianoCore boot splash

Thank you for your detailed response!

So if I understand you correctly, you are saying that from now on the issue lies within the guest OS, and thus I am rather limited in what I can do on my end. The good news is that I have actually gotten it to work with a Windows 10 guest. Running Windows was my actual goal, so not being able to pass the GPU to a Linux guest is not the end of the world for me.

I realized that the current setup is probably not very practical for me in the long run, though, as I now only have the integrated Intel GPU for my host to use, which will be quite a limitation for games and other graphics-intense applications. Therefore I am now considering getting a second card. You mentioned the GTX 750 (and Alex seems to have used this one successfully, too). Does it work well for you? If so, I might just try to get one of those. It should also be more or less on the same level of performance compared to the HD 7850 I am currently using.

On Wed, Apr 31, 2016 at 12:03 AM, Laszlo Ersek wrote:
On 04/12/16 20:42, Stefan Seil wrote:
As far as I can tell, the other PCI device is the HDMI audio controller
of the graphics card. It is listed as a seperate PCI device and I
assigned it to the VM, too.
I think that makes sense. I have the same situation with my GTX750. I
believe those two functions belong to the same IOMMU domain, so they
have to be assigned together anyway.

I haven't explicitly added any USB devices, although it seems like there
are some per default. I have linked the respective domain XMLs below.
Hmm no, as far as device assignment goes, you have only two <hostdev>

Regarding USB devices, you have a few emulated controllers. As far as
actual devices go, you seem to be using Spice USB redirection (see
<redirdev>). I had to read up on that:

I can't tell if you actually redirected some host-side USB devices. I
think it's unlikely; Cole's blog post says "When connected to a VM's
graphical display", and in your first domain XML, your only display is
the assigned GPU (no <graphics> element).

I have played around with the configuration a bit and removed the rom
file for the HDMI audio controller of the graphics card (previously I
had given it the same rom file as the one I passed to the GPU)
Aha! So that is why I saw two instances of AmdGop.efi.

(I think there may be a bug in AmdGop.efi. A UEFI_DRIVER must cope with
the situation when the PciIo protocol interface on the device handle is
already open by another (or the same) driver.)

and now
the VM actually does not stop at the TianoCore logo anymore. The monitor
now displays the GRUB menu

and turns black after choosing the first boot
entry. This is the new log now: http://pastebin.com/2dxBqP6h
Yes, this one dispatches AmdGop.efi only once. I can also see
shimx64.efi and grubx64.efi in the log.

I have also configured the VM with emulated graphics using QXL (just the
standard configuration you get with the setup wizard). If I try to boot
with the GPU passed through in addition to having the emulated graphics,
I can see it progressing further on the emulated display. It looks like
it starts booting the OS and then stops at this line:

intel_rapl: no valid rapl domains found in package 0

I don't see any of that on the monitor connected to the graphics card,
The point is, by eliminating the romfile for the HDMI audio controller,
you managed to reach grub, and grub actually started your kernel. (The
above intel_rapl message comes from "drivers/powercap/intel_rapl.c".)

 From this point on, it is a guest kernel / guest GPU driver question.
Since you do have functional grub, I recommend the following:

* Edit your domain configuration so that it has an emulated serial
console. Virtio-serial is *not* good enough. Run "virsh edit", and add
the following:

     <serial type='pty'>
       <target port='0'/>
     <console type='pty'>
       <target type='serial' port='0'/>

... Actually, I'm just noticing that your second XML paste, at
<http://pastebin.com/Wm3E23nW>, already contains this XML fragment. Good.

* Create the $HOME/.screenrc file, with the following content:

logfile /tmp/screen.log
logfile flush 1

* Start the VM like this, from the shell:

   # launch "screen" first

   # now press [Ctrl-A Shift-H]
   # this will start logging terminal traffic to the logfile

   # launch the guest
   virsh start --console --paused xubuntu-clone

* Wait until the line "Connected to domain xubuntu-clone" appears.

* Now open the guest in virt-manager as well, and click the Pause button
to unpause the guest.

* As soon as the grub menu appears, choose to edit the kernel command
line, under the first grub menu entry (i.e., the one that you would
normally boot).

If the "quiet" parameter is there, remove it.

Independently, add the following three parameters:

   console=tty console=ttyS0,115200 ignore_loglevel

* Boot the edited command line.

* When the guest becomes stuck again, force it off (using virt-manager),
same as before. This will also make "virsh" return in your "screen"
window, and then you can type "exit" there.

* Email the /tmp/screen.log file, with the guest kernel's debug output,
to whoever provided your guest kernel. :)


These are the two domain XMLs now:
Without additional emulated graphics: http://pastebin.com/hBTdP6Sq
With additional emulated graphics: http://pastebin.com/Wm3E23nW

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