Using memory already page-locked by a driver?

I have a Windows PCIe driver kernel that allocates, page-locks, and maps to userspace a relatively large chunk of memory. I was wondering if there is a way to use it directly as it is already pinned? Are there any other requirements for the allocated physical memory?

I’ve tried to use cudaHostRegister, with both the default as well as the cudaHostRegisterIoMemory flag, but get back cudaErrorUnknown for both configurations. Is this expected?