Enabling KVM for AMD leads to boot hang

[MadWhiteCat]

Hello everyone,

I've been following Gentoo QEMU setup instructions.
I enabled "Virtualization -> KVM for AMD processors support" kernel option (I have Ryzen 7 9800X3D), as well as virtualization support (SVM Mode) in BIOS.
After building kernel and rebooting, the system hangs indefinitely at either "Setting system clock using the hardware clock" or "Activating swap devices" - seemingly random on each reboot.

What made no difference:
- Setting "KVM for AMD processors support" as built-in or module
- Enabling other kernel options suggested in the QEMU guide (Intel module and "Useful kernel configuration options")

I also checked that I have IOMMU enabled in BIOS and valid IOMMU groups according to this Arch Wiki guide.

Tried seeing if anything useful appears in /var/log/rc.log (I enabled logging in /etc/rc.conf), but it seems that writing starts after these failure points. The log file wasn't updated on unsuccessful boots - I checked its contents from my Windows installation after a failed Gentoo boot.

What can I do to debug this further? Has anyone seen a similar problem before?

[Anon-E-moose]

Did you set IOMMU_DEFAULT_PASSTHROUGH
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UM780, 6.12 zen kernel, gcc 13, openrc, wayland

[MadWhiteCat]

Tried this now, rebuilt kernel - still got stuck at "Activating swap devices".

[Anon-E-moose]

sounds like not all of the kvm stuff is set or set right.

Best to have kvm as a separate module, but kvm_amd needs to also be set the same way (both modules or both built in)

wgetpaste your .config file and maybe something will show there.
_________________
UM780, 6.12 zen kernel, gcc 13, openrc, wayland

[MadWhiteCat]

Tried building everything as module, no difference.
Here's my .config - https://0x0.st/8SsR.txt