[SOLVED] Can't use separate graphic output in virt-manager

Operating Systems & Open Source Linux
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Short version:

I have the guest OS up and running, but the graphic card is with error code 43, and can’t see any output in the second monitor input.

Long version:

I’m following this guide, my setup is: 3700x + B450 Tomahawk Max, 5700xt (guest) + 750Ti (host), 32 GB RAM. But I have an old monitor, VIseo223DX, which is pretty dumb, but currently I can’t afford any expense (as much as I hate TN, it was instant dislike the very first time I saw them). And because it’s a dumb monitor it only has two inputs: DVI and VGA. The 5700xt has an HDMI cable with an HDMI->DVI adapter, while the 750Ti has a VGA-VGA cable. It runs at 1080, with a little bit of .rc coercion, and with slight shadows (which I can grudgingly live with, until the day of reckoning). This means that I can’t have both outputs active.

I discovered here that I can use the already existent partitions with Windows and, to my great surprise, it works. All I had to do was to install a few drivers from the fedora iso. But the graphics card is listed with the dreaded yellow exclamation mark, code 43. Before using the old Windows partitions, I already managed to install a fresh copy on a qcow2 filesystem, which also worked, but with the same problem.

Searching for solutions, I saw this, which I followed to the letter (except address and bus thingies, particular to my setup). Same thing. Then I saw this which said to remove the spice video, the QXL, and the console. Now, the minor problem is that the first partition it sees, no matter how I arrange the disks, is the recovery partition; but I need the 2nd one, so I need to enter the Tian BIOS and manually boot it. It works, but that just means I need the console. And I can’t delete the QXL while there is a spice video, and deleting the spice means no console (just some blank screen with a cursor, nothing else, in the virt-manager’s window).

After booting the guest, if I switch over to the 2nd input (DVI), all I see is a blank screen. If I delete the spice + QXL (with or without console), the second output acts as if it has no signal, because changing the inputs through the monitor’s menu lasts for 1-2 sec, after which it automatically reverts to the 1st input (VGA).

Does someone have any little idea about what goes wrong? What can I do to have the 2nd output working (or not get the code 43)?

2

I ended up playing piano with the buttons and settings, and now it works. Two settings that I can see and identify as being the cause (possibly others, sorry, can’t remember all the pushed buttons): I had to desable “ROM bar” in BIOS, and instead of the “spice” video, I used “VNC”. I left the console and the “QXL”. I’m not sure if I could have left the BIOS and just disabled it from the .xml, because I already had it with <rom bar="off" .../>, and the result was in the OP.

As it is, it runs, at least until I shut it down, then it refuses to start with unknown PCI header '127'. It looks like it’s related to the AMD reset bug, because I get the same !!! Unknown header type 7f with lspci -vvn. A reset cures it, or I can just keep the VM running. Also, the sound is gone, the mouse is a bit untamed, the file transfer seems to be about 50% (+/-), but those are other problems. Anyway, the original issue is gone and the above seems to be the solution (at least in my case). I’ll mark this as solved (and hope it stays that way).