Arch Linux

HolyKnightofthe7th

Member

Registered: 2020-12-13

Posts: 3

[SOLVED]Segmentation fault when trying to unbined the efi-framebuffer

So i have been trying to do a single Gpu passthrough for a while now, but i can't really figure out how to unbined the efi-framebuffer. it is a need step to detach the Gpu from linux. and when i always try to run the script from an ssh client i always get segmentation fault when trying to execute: echo efi-framebuffer.0 > /sys/bus/platform/drivers/efi-framebuffer/unbind.
From what i have read segmentation fault is when you try to access a protected part of memory and you don't have access even though i did execute it with sudo. is there anyway to unbined it?

Last edited by HolyKnightofthe7th (2021-01-01 18:07:17)

Head_on_a_Stick

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From: The Wirral

Registered: 2014-02-20

Posts: 9,003

Website

Re: [SOLVED]Segmentation fault when trying to unbined the efi-framebuffer

Did you unbind the VT consoles before attempting to unbind the framebuffer?

# echo 0 > /sys/class/vtconsole/vtcon0/bind
# echo 0 > /sys/class/vtconsole/vtcon1/bind

See also https://github.com/joeknock90/Single-GPU-Passthrough

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Jin, Jîyan, Azadî

HolyKnightofthe7th

Member

Registered: 2020-12-13

Posts: 3

Re: [SOLVED]Segmentation fault when trying to unbined the efi-framebuffer

Sorry for the very long gap, and yep i have tried unbinding the VT console before the framebuffer, and they both go without a problem. The exact output of the script from the github repo you mentioned is: (i have edited some parts like for example my display manager and my pci ids but i believe these don't affect it as my screen goes black which means my display manager is stopped and the ids act much later in the script)

+ source /etc/libvirt/hooks/kvm.conf
++ VIRSH_GPU_VIDEO=pci_0000_26_00_0
++ VIRSH_GPU_AUDIO=pci_0000_26_00_1
++ VIRSH_GPU_USB=pci_0000_26_00_2
++ VIRSH_GPU_SERIAL=pci_0000_26_00_3
+ systemctl stop lightdm.service
+ echo 0
+ echo 0
+ echo efi-framebuffer 0
Segmentation fault (core dumped)

as you can see the VT consoles both unbined but the efi-framebuffer doesn't, i should also mention that i use Nouveau drivers instead of the propritery ones. i have been able to unbined the efi-framebuffer with nomodeset in my kernel parameter but even then i have not been able to start the VM properly, like it starts but it doesn't output anything just an endless void.

Last edited by HolyKnightofthe7th (2020-12-30 11:21:08)

Head_on_a_Stick

Member

From: The Wirral

Registered: 2014-02-20

Posts: 9,003

Website

Re: [SOLVED]Segmentation fault when trying to unbined the efi-framebuffer

All I can suggest is debugging the segfault: https://wiki.archlinux.org/index.php/Co … _core_dump

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Jin, Jîyan, Azadî

HolyKnightofthe7th

Member

Registered: 2020-12-13

Posts: 3

Re: [SOLVED]Segmentation fault when trying to unbined the efi-framebuffer

Thank you for your help, currently i have successfully done a single gpu passthrough if only it is using the temporary solution of just adding "nomodeset" to my boot parameters then rebooting and launching my VM through the tty. Though i am stuck on code 43 but that is another story, for now i mark this thread as solved. Don't really know what causes the efi-framebuffer to lock down but it probably is related to using nouveau.