graphic: 0.734
device: 0.725
files: 0.687
risc-v: 0.648
register: 0.512
debug: 0.503
architecture: 0.492
permissions: 0.483
semantic: 0.472
performance: 0.452
network: 0.448
vnc: 0.436
socket: 0.412
PID: 0.336
arm: 0.322
boot: 0.320
ppc: 0.318
mistranslation: 0.309
virtual: 0.296
i386: 0.295
peripherals: 0.246
TCG: 0.214
VMM: 0.199
x86: 0.195
user-level: 0.194
kernel: 0.184
hypervisor: 0.164
KVM: 0.084
assembly: 0.052

The cause code of a trap changes when qemu is nested in another qemu
Description of problem:
I am studying the feasibility of doing some practical work on RISCV plates. Since I don't have these boards yet, I'm emulating it with qemu. The practice in turn consists of launching with qemu a very small operating system with two tasks that make a series of system calls.

When I run this practice on my host it works correctly, but when I run it on an Ubuntu emulated in riscv with qemu, the cause code for the trap changes (the first bit of the code).

The demo can be found in this repository: https://github.com/Sft570/qemu-bug-report
Steps to reproduce:
1. Clone the repository on the host and run the demo with "make qemu"
2. Emulate with qemu ubuntu in riscv, clone the repository and run the demo with "make qemu".

The error displayed shows the change of the cause code bit. You can analyze its behavior in the trap.c file in the src folder.
Additional information: