Re: [Qemu-devel] [PATCH 7/7] PPC64: Don't fault at lwsync

[Paul Brook]

> If anyone knows how to really fix this, please step forward and do
> so. This only makes things work at all for me :-).

I bet lwsync being a nop is a clue.

When an MMU exception occurs, qemu figures out the guest location from the 
location of the MMU access in guest code (see cpu_restore_state). My guess is 
that this breaks when two guest instructions have the same location. I'm not 
entirely sure what the correct fix is, or where the bug lies 
(cpu_restore_state,  gen_intermediate_code_pc, or tcg_gen_code_search_pc) but 
hopefully this will point you in the right direction.

One thing to try (to confirm this theory) is make lwsync do domething (write 
to a dummy register or call a helper function) and see if the problem goes 
away.

Paul