Depends which brain. There are some people I know I suspect you could simulate with a potato and a few wires.

Do you think there will be qemu-system-hbrain when that happens?

https://flybrain.app/

I know you mean human brain, but the point is that the principles largely exist and the progress is accelerating.

However, one of the key learnings from the linked project is that the brain and body are intrinsically linked and biology is a nightmare mess of spaghetti code. Simulating just the brain has limited benefits and will not likely simulate a person or consciousness any more than simulating small pieces of a brain.

For some further reading: https://www.sciencedirect.com/science/article/abs/pii/S030645222100021X (scihub)