On Sat, Jan 29, 2022 at 12:46:59PM +0100, Greg Kroah-Hartman wrote:
> 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?
Ah, true, not sure how I ended up checking out the 5.9 stable branch
(maybe I had 4.9 in mind for an unrelated thing and just thought of
something .9).
I'll send you a backport to 5.10.
--
Catalin
