My previous Proxmox post described how to install Sierra into Proxmox using the Enoch bootloader (SeaBIOS boot). Since then, I’ve been using it as my daily-use desktop, and it has generally been working out great for me. However, I had some real struggles getting the graphics card passthrough to work reliably. I managed to fix these by updating to UEFI boot with Clover.
One of the problems with legacy BIOS boot and GPU passthrough is VGA arbitration. From what I understand, the video cards in the host and guest can end up both contending to own the VGA resources, which can cause a deadlock on boot. When a Sierra guest loads its video driver during boot, my Proxmox host hangs, and the screen fills with black and white bars.
UEFI boot doesn’t suffer from this problem, since it does away with the legacy VGA interface. So if your video card’s firmware supports UEFI/EFI boot (my R9 280X already does), you can switch the guest to boot using OVMF instead. This requires us to use a macOS bootloader that supports UEFI. I chose Clover. Continue reading Using Clover UEFI boot with Sierra on Proxmox