Re: NVMM on non-x86?

[Chris Hanson <cmhanson%eschatologist.net@localhost>]

On Feb 16, 2020, at 10:26 PM, Martin Husemann <martin%duskware.de@localhost> wrote:
> 
> On Sun, Feb 16, 2020 at 09:10:40PM -0800, Chris Hanson wrote:
> 
>> Has anyone worked on support for NVMM for non-x86 systems, such as
>> m68k, PowerPC, MIPS, or ARM?
> 
> NVMM only helps qemu (or whatever emulator) if the CPU has good enough
> virtualization features. Even older x86 CPUs do not have that. I am pretty
> sure all m68k cpus I have do not have that either.

My understanding is that the x86 CPUs have generally had poor virtualization features in that it’s difficult to trap and handle all higher privilege instructions accurately. Most other CPU architectures from the mid-1980s on don’t have that problem. (The 68000 had an equivalent issue, it was addressed with the 68010.)

> Newer ARM ones definitively do, and we are looking forward for support
> for them in NVMM (but no concrete plans, as far as I know).

I know there are a number of tools in modern architectures to make virtualization easier, whether related to handling supervisor accesses, maintaining hypervisor page tables, and so on, but if an architecture supports virtualization at all why exclude it from the virtualization API?

  — Chris