Request for Guidance to Add Cortex-M7 (ARMv7-M) Support in QBox

[Aabhash23]

Hello QBox Team @alwalidsalama @MarceronT ,

I am trying to use QBox with QEMU’s Cortex-M7 (ARMv7-M) CPU, which is part of the arm-softmmu target. QBox currently supports AArch64 and other architectures through libqemu, but ARM32 / Cortex-M support seems to be missing.

What I am trying to achieve

Enable QBox to load and run QEMU’s ARM32 targets, specifically Cortex-M CPUs such as:

-M mps2-an500 -cpu cortex-m7

What I have tried

Updated qemu.cmake to add arm-softmmu to the target list.

Updated the main CMakeLists to generate libqemu-arm.

Tried enabling ARM32 targets similarly to existing AArch64, RISC-V, etc.

But ran into several build issues:

Missing libqemu-arm target

Duplicate target creation errors

Conflicts between interface libraries and generated shared libraries

What I need

Could you please clarify:

Is ARM32 / Cortex-M support currently expected to work with QBox?

Which QEMU version should be used for adding ARM softmmu support?

What is the correct way to extend QBox’s build system (CMake + qemu.cmake) to add a new QEMU target?

Are there any known limitations or required patches when adding ARM32 targets to libqemu?

[androm3da]

QBox contains wrappers of ARM CPU and device models. System models / machines "cannot" be included into QBox. Instead, the equivalent QEMU machine can be composed in SystemC using a combination of QEMU CPUs, QEMU devices, SystemC devices.

cortex-m7 is one of the models that's provided in QBox today.

Maybe it would be helpful for us to make a test case to illustrate how it can be used?

[Aabhash23]

Thank you for your previous clarification.
I now understand that Cortex-M7 models are already available inside QBox, and that full QEMU “machines” cannot be imported directly. Instead, the equivalent machine must be assembled manually using QEMU CPU + device wrappers + SystemC components.
To move forward, I need help with one specific use-case:
My Goal
I need to build a minimal QBox-based platform that:

Uses a Cortex-M7 CPU,

Runs a bare-metal or FreeRTOS application,

And can send and receive Ethernet packets (e.g., respond to ping, generate packets, or react to an external trigger).

Where I Need Guidance
Since QBox only provides CPU/device wrappers and not full machines, I’m unsure how to compose the correct set of components.
Could you please clarify the following:

1. How to instantiate the Cortex-M7 CPU wrapper correctly?

What is the correct QEMU CPU type string to pass?

Is there a dedicated wrapper for Cortex-M7 (e.g., qemu::CpuArm) or should I use arm-cpu with specific properties?

2. Which QEMU or SystemC components should be connected for an M7 platform with Ethernet?
   For example:

NVIC

SysTick / timer

RAM / Flash

Ethernet MAC / PHY device supported by QEMU / QBox

Any required bus / router / sysbus setup

I need to know which exact blocks must be created to enable Ethernet functionality.
3. How to connect the Ethernet device to the CPU and expose it externally?

Should I use a QEMU NIC model (e.g., stellaris_enet, lan9118, etc.)?

Or a SystemC MAC/PHY component from the QBox library?

How are interrupts wired (Ethernet IRQ → NVIC)?

How to connect the NIC to a TAP interface or socket so the application running on M7 can receive a ping?

4. How to load and start my M7 application?

Should I use qemu::Loader to load the ELF?

Do I need to manually configure vector table offset or reset address?

5. If you already have an internal test or example for Cortex-M Ethernet usage, could you share it or point to it?

A minimal working example or step-by-step outline would be extremely helpful, since this involves combining QEMU’s Cortex-M7 model, interrupt controller, memory, and Ethernet device inside a SystemC environment.
Thank you for your help!

[markfoodyburton]

What do you mean machines can't be imported directly?
There are existing platforms in qbox, there are 2 that are close to what you need, I suggest you take a look at the A76 Ubuntu platform, and perhaps the m55 remote platform (though I dont think you need the 'remote' aspect of that). You should be able to work out how to build what you need from those two.

[androm3da]

What do you mean machines can't be imported directly?

@Aabhash23 is citing my comment from above. QEMU machines define the instantiation/wiring among CPUs, memory and devices. This is out of scope for libqemu (not explicitly exported) and QBox provides its own definitions of these.

the A76 Ubuntu platform, and perhaps the m55 remote platform

The A76 is 64-bit, though, isn't it? But yeah m55 is 32-bit I think.

[Aabhash23]

Hi i got you but i am specifically looking for cotex-m7 chip i know i can emulate it in standalone qemu but how to use that in qbox because qbox is using its own definitions of these and as far as i know cortex-m7 definition is not there in the qbox.So i need help specifically regarding that. Thanks in advance.

[markfoodyburton]

If you follow the way the e.g. M55 is done, then you can add a new processor model really easily. If you manage to get it working a patch would always be welcome :-)