x86 virtualization on Ryzen

With the relatively new generic virtualization interface, Seoul is now able to run on my AMD Ryzen machine. However, VirtualBox still crashes when starting the VM. With the NOVA-specific interface, it would die from an unresolved page fault, while with the generic interface, it throws a general exception that doesn't seem to give much information. I don't have the log on hand right now; otherwise I would specify the exception. What differences are there that could make VirtualBox fail while Seoul works fine? My UEFI version should be new enough to have the Ryzen CPUID issue patched, so that shouldn't be the problem, but I don't know how to empirically rule that out.