TL DR

Step 1) Add

-object memory-backend-file,id=mem,size=512M,mem-path=/dev/shm/qemu-ram,share=on -machine memory-backend=mem

To your QEMU command

Note : Choose the correct size, the same as specified by -m, here -m 512m, therefore size=512M.

Step 2) Open /dev/shm/qemu-ram from your external process

Step 3) Profit !

Initially QEMU was an emulation engine, with a Just-In-Time compiler (TCG). The TCG is here to dynamically translate target instruction set architecture (ISA) to host ISA.

qemu-system-aarch64 --accel ?
Accelerators supported in QEMU binary:
tcg

The QEMU Human Monitor Interface (HMI) console provides an interface that allows user interaction with a running virtual machine instance. It enables obtaining memory dumps, viewing the virtual device tree, taking screenshots, performing audio grabs and much more. This entry covers a few interesting examples.