> Maybe it would be interesting to know from which patch the error comes.
It’s hard to attribute this to a single commit, but the distance between r10’s save location and r11-r12’s save location has definitely grown over time. The comment is introduced in commit 7180e3e636de ("[POWERPC] force 64bit mode in fwnmi handlers to workaround firmware bugs”) way back in 2006. In v3 will insert another comment to better signal where r11-r12 are saved.