QEMU riscv32-softmmu, what does the softmmu mean?

Question

Does the 'softmmu' mean that the virtual machine has a single linear address space available to machine and user mode? Or does it have some virtual memory capabilities that are implemented via software and not the underlying processor? Or maybe it means something different entirely?

Buyer

Answer 1

-softmmu as a suffix in QEMU target names means "complete system emulation including an emulated MMU, for running entire guest OSes or bare metal programs". It is opposed to QEMU's -linux-user mode, which means "emulates a single Linux binary only, translating syscalls it makes into syscalls on the host". Building the foo-softmmu target will give you a qemu-system-foo executable; building foo-linux-user will give you a qemu-foo executable.

So a CPU emulated by -softmmu should provide all the facilities that the real guest CPU's hardware MMU provides, which usually means multiple address spaces which can be configured via the guest code setting up page tables and enabling the MMU.

Sandman