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#1 2019-05-18 17:53:26

Aex12
Member
Registered: 2019-05-18
Posts: 6

[SOLVED] TTY* displaying on secondary GPU.

Hi, I got this problem for a while and I cant find anything related on the internet.

I have a dual GPU setup, my main GPU is an Intel IGFX, and my secondary GPU is a RX580 which I exclusively use for passthroughing it to a Windows VM. I have two screens attached to my IGFX, and one TV attached to the RX580 which I use to play some games. I dont have any display manager (neither I want it). I use startx to start the X server. I have configured my UEFI to use my IGFX as my main VGA.

The problem is whenever a display is connected to the RX580 it will output the TTYs there. If I dont connect anything, the TTYs will be displayed on my main screen. It's annoying for me to have ttys on my TV, and very unpractical, because I have to blindly enter my username+password+startx or turn on my tv.

Things I have tried with no sucess:
- Blacklisting both amdgpu and radeon drivers
- GPU pci-stubbed (as it is required for the GPU-Passthrough to work)
- Setting my main GPU on bios as my IGFX.
- Checked /etc/systemd/logind.conf but found nothing related to displays.

The only thing that works is disconnecting any display on the GPU before powering on my machine, and then replug it, but it is so annoying to do this every time I need TTYs working on my main screen.

Any suggestions? Thanks in advance!

Last edited by Aex12 (2019-05-19 13:08:47)

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#2 2019-05-18 19:45:45

seth
Member
Registered: 2012-09-03
Posts: 49,959

Re: [SOLVED] TTY* displaying on secondary GPU.

a) autologin & startx into a locked session
b) you could try to blacklist the amdgpu module and only load it on demand (but I've no idea whether that'll actually solve the problem, also you better only blacklist at the kernel command line in case things break badly)

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#3 2019-05-18 19:50:00

Aex12
Member
Registered: 2019-05-18
Posts: 6

Re: [SOLVED] TTY* displaying on secondary GPU.

seth wrote:

a) autologin & startx into a locked session
b) you could try to blacklist the amdgpu module and only load it on demand (but I've no idea whether that'll actually solve the problem, also you better only blacklist at the kernel command line in case things break badly)

Well, maybe A would be an option, but I don't like to autologin to my account, since this will be an huge security breach. I don't also like starting x straight away after boot. And still doesn't solve the problem of accessing TTYs after login with Control+Alt+F2/3/4... if I need to use them.

Point B is already tested as mentioned on the OP, and it doesn't fix it either.

I'm completely sure there is a way to change the display where TTYs are rendered, it's is just that I can't figure out how

Last edited by Aex12 (2019-05-18 19:55:16)

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#4 2019-05-18 19:55:28

seth
Member
Registered: 2012-09-03
Posts: 49,959

Re: [SOLVED] TTY* displaying on secondary GPU.

What happened when you tried to blacklist amdgpu/radeon? Did you still get output on the AMD output??

Fwwi, what do you consider to be a "huge" security breach about logging into a locked session?

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#5 2019-05-18 20:02:54

Aex12
Member
Registered: 2019-05-18
Posts: 6

Re: [SOLVED] TTY* displaying on secondary GPU.

seth wrote:

What happened when you tried to blacklist amdgpu/radeon? Did you still get output on the AMD output??

Fwwi, what do you consider to be a "huge" security breach about logging into a locked session?

I'm sorry, I didn't read that part. Anyway, this still autostart X after boot, which I don't want (this is why I don't use any display manager), and still doesn't solve the problem of accessing TTYs after login.

When I blacklist amdgpu and radeon drivers, it boot as normal and still display ttys on the RX580. lspci show that rx580 is using the pcistub driver.
(Which should avoid the use of the GPU, so I don't understand how it is able to still display ttys). X server can't use the GPU (Which is fine). I just want tty to also dont use it.

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#6 2019-05-19 07:07:47

seth
Member
Registered: 2012-09-03
Posts: 49,959

Re: [SOLVED] TTY* displaying on secondary GPU.

ls /dev/fb*

?

Pass

fbcon=map:<n>

to try to get it to use the IGP framebuffer (iff there are separate framebuffers)
See https://www.kernel.org/doc/Documentation/fb/fbcon.txt on details.

But beyond that I'm out of ideas, sorry. Controlling the TTY output is an open problem (esp. on single GPU, multi-output setups it seems completely impossible)

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#7 2019-05-19 08:30:04

Aex12
Member
Registered: 2019-05-18
Posts: 6

Re: [SOLVED] TTY* displaying on secondary GPU.

seth wrote:
ls /dev/fb*

?

Pass

fbcon=map:<n>

to try to get it to use the IGP framebuffer (iff there are separate framebuffers)
See https://www.kernel.org/doc/Documentation/fb/fbcon.txt on details.

But beyond that I'm out of ideas, sorry. Controlling the TTY output is an open problem (esp. on single GPU, multi-output setups it seems completely impossible)

This is what I was looking for. So many thanks!

Used fbcon=map:1 and now TTYs are displaying correctly on my IGFX.

For future lost souls who arrives here by Google:

running "cat /proc/fb" will tell you what framebuffers can you use, along with their name and id. Just update your boot options accordingly and reboot.

Last edited by Aex12 (2019-05-19 08:39:01)

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#8 2019-05-19 13:06:12

seth
Member
Registered: 2012-09-03
Posts: 49,959

Re: [SOLVED] TTY* displaying on secondary GPU.

Cool.
Please always remember to mark resolved threads by editing your initial posts subject - so others will know that there's no task left, but maybe a solution to find.
Thanks.

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#9 2019-05-19 13:08:25

Aex12
Member
Registered: 2019-05-18
Posts: 6

Re: [SOLVED] TTY* displaying on secondary GPU.

seth wrote:

Cool.
Please always remember to mark resolved threads by editing your initial posts subject - so others will know that there's no task left, but maybe a solution to find.
Thanks.

You're right, I forgot to edit it.

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