The large barrier is bounce-buffer mapping: SPDK requires hugepagesI think we can support registering user space memory for bounce-buffer
for NVMe over PCIe and RDMA, so take some preallcoated hugepages to
map as bounce buffer is necessary. Or it's hard to avoid an extra
memcpy from bounce-buffer to hugepage.
If you can add an option to map hugepages as bounce-buffer,
then SPDK could also be a potential user of vduse.
use like XDP does. But this needs to pin the pages, so I didn't
consider it in this initial version.