[Qemu-devel] Using memory mapped IO to read and write in guest memory data

[lkn2993]

Hi all.

I have been searching thoroughly for the latest requirement I need to fulfill 
using QEMU.
The scenario is like this:
• I have another simulator which is a C program, this program has a shared 
memory which can be exposed to a file when need be, it can also write to an 
address or read from it when required
• I have a machine which runs FreeRTOS via QEMU, not the best operating system 
out there, I know. But it can accept interrupts and jump to the specified 
memory regions upon receiving it, so if QEMU has an address that I can write to 
using the external simulator application, then I can interrupt the OS to read 
the address for changes afterwards.
IMHO I have figured out that I can actually create MMIO to map an IO into 
memory address, but I cant seem to figure out the how tos that have been 
written to expose this feature.

• So how can I actually initialize a memory mapped IO in qemu options(upon 
runtime or build)?
• How can I read and write into it, The aforementioned C program can write 
freely to anything I desire, where and what should I write, where and how 
should I read(from memory mapped IO)

Are there also other alternatives to solve this problem? Like, can I actually 
use a file as the QEMU guest system memory and write to it and read from it 
with free will? Or is there a way to attach a process to QEMU that can see and 
edit its guest memory?

Thanks in advance.