Re: Qemu system mode emulation for heterogeneous SOC

[Peter Maydell]

On Tue, 14 Apr 2020 at 23:08, Ancuta, Cristian
<address@hidden> wrote:
> As the subject says, I was wondering if QEMU execution model allows the full 
> system emulation of a custom heterogeneous SoC architecture.

Only in the very limited sense "you can have two different CPUs which
are of the same architecture", eg an Arm M-class core and an A-class
core. You can't have two CPUs which are entirely different architectures
(eg PPC and Arm). In principle this would be nice to be able to do, but
in practice QEMU's current source tree assumes that various properties
of the guest CPU are compile-time fixed, and making those all be
"this is actually a variable property that applies only to some of the
CPUs being emulated" rather than just "this is set by a #define" would
be a massive effort.

> As a related question, is MMIO supported in user mode emulation?

No. Much of the infrastructure and framework for device emulation
is only in the -softmmu binaries. The user-mode emulation stuff
is intended for emulating single Linux userspace processes, which
don't have direct access to device hardware.

thanks
-- PMM