On Fri, Jan 28, 2022 at 06:53:01PM +0000, Catalin Marinas wrote: > From: D Scott Phillips <scott@xxxxxxxxxxxxxxxxxxxxxx> > > commit 38e0257e0e6f4fef2aa2966b089b56a8b1cfb75c upstream. > > The erratum 1418040 workaround enables CNTVCT_EL1 access trapping in EL0 > when executing compat threads. The workaround is applied when switching > between tasks, but the need for the workaround could also change at an > exec(), when a non-compat task execs a compat binary or vice versa. Apply > the workaround in arch_setup_new_exec(). > > This leaves a small window of time between SET_PERSONALITY and > arch_setup_new_exec where preemption could occur and confuse the old > workaround logic that compares TIF_32BIT between prev and next. Instead, we > can just read cntkctl to make sure it's in the state that the next task > needs. I measured cntkctl read time to be about the same as a mov from a > general-purpose register on N1. Update the workaround logic to examine the > current value of cntkctl instead of the previous task's compat state. > > Fixes: d49f7d7376d0 ("arm64: Move handling of erratum 1418040 into C code") > Cc: <stable@xxxxxxxxxxxxxxx> # 5.9.x 5.9.x is long end-of-life, did you mean to do this for 5.10.y? If so, it does not apply cleanly there :( thanks, greg k-h