BTMMU: an efficient and versatile cross-ISA memory virtualization
Kele Huang, Fuxin Zhang, Cun Li, Gen Niu, Jun-Rong Wu, Tianyi Liu · 2021
Full system dynamic binary translation (DBT) has many important applications, but it is typically much slower than the native host. One major overhead in full system DBT comes from cross-ISA memory virtualization, where multi-level memory address translation is needed to map guest virtual address into host physical address. Like the SoftMMU used in the popular open-source emulator QEMU, software-based memory virtualization solutions are not efficient. Meanwhile, mature techniques for same-ISA virtualization such as shadow page table or second level address translation are not directly applicable due to cross-ISA difficulties. Some previous studies achieved significant speedup by utilizing existing hardware (TLB or virtualization hardware) of the host. However, since the hardware is not designed with cross-ISA in mind, those solutions had some limitations that were hard to overcome. Most of them only supported guests with smaller virtual address space than the host. Some supported only guests with the same page size. And some did not support privileged memory accesses.