First post here, did a search first and didn’t find anything related, but if I made newbie mistakes by posting, please let me know.
I’m close to complete my home server setup, Proxmox on 12700K, ASUS TUF Z690 D4, Sapphire Pulse 6700 XT, some linux VMs for various things, a Windows VM for gaming, typical stuff. I had the GPU passthrough to Windows, luckily this card doesn’t seem to suffer from the AMD reset bug, it worked well in Windows, VM can reboot.
However, today after I reboot the host machine, passthrough stopped working. I was able to track down the cause to the “above 4g decoding” BIOS setting, it was turned on by itself for some reason. This setting caused trouble before so I can be sure I turned it off. To verify, I turned it off and reboot the host again, it was back on. I turned it off again, this time I entered BIOS again immediately, it was back on…
Can anyone explain this behavior? I suspect it’s an ASUS BIOS bug, maybe there are other conflicting BIOS settings forcing this one to be enabled, but for some reason it failed to acknowledge the user? I’ll contact ASUS support tomorrow during their business hours but would love to know if there’s a solution.
No, just this one setting. I changed quite some BIOS settings, one that’s right next to “above 4g decoding” is SR-IOV, it was off by default, I turned it on for iGPU passthrough, it didn’t work but I left SR-IOV on, it stays on between reboots. I also change fan curve, those settings stick.
Is your BIOS fully updated? Might be worth reflashing it even if so just to see if it still happens, or reverting to a previous version if it is possibly a bug with the current version.
SR-IOV and above 4G decoding are probably linked settings
This is it! Disabling SR-IOV makes the 4g decoding setting stay disabled too! Thank you @tjw!
Not sure if they should be connected though because the SR-IOV description says it depends on native PCI power control to be enabled, but not above 4g decoding. Also, I tried to keep SR-IOV enabled, 4g decoding disabled, save and exit. GPU passthrough works, rebooting host without entering BIOS, passthrough still work. It seems the setting only auto turns on when entering the BIOS screen. I did entered BIOS earlier today to check my fan curve, passthrough broke after that.
Above 4GB decoding turned off caused a problem? Sounds like a dev needs to update some shit. Below 4GB decoding is just to support ancient 32 bit garbage.