I think I may have missed the Windows reset in my previous trace. A new one shows subsequent activity to the above APIC writes. This is on a VM guest running on top of Xen. The last write is the IOPORT write to 0x64.

CPU0 857940486111 (+ 0) CPUID [ func = 0x00000001, eax = 0x000206a7, ebx = 00200800, ecx = 8e982201, edx = 0x1789fbff ]
CPU0 857940488848 (+ 0) CPUID [ func = 0x40000001, eax = 0x31237648, ebx = 00000000, ecx = 00000000, edx = 0x00000000 ]
CCPU0 857940491234 (+ 0) CPUID [ func = 0x40000004, eax = 0x00000028, ebx = 000007ff, ecx = 00000000, edx = 0x00000000 ]
CPU0 857940493712 (+ 0) IOPORT_WRT [ port = 0x00000064, data = 0x00fe ]