[PATCHv3] arm64: initialize per-cpu offsets earlier

[Will Deacon]

On Tue, Mar 02, 2021 at 11:53:35AM +0000, Mark Rutland wrote:
> The current initialization of the per-cpu offset register is difficult
> to follow and this initialization is not always early enough for
> upcoming instrumentation with KCSAN, where the instrumentation callbacks
> use the per-cpu offset.
> 
> To make it possible to support KCSAN, and to simplify reasoning about
> early bringup code, let's initialize the per-cpu offset earlier, before
> we run any C code that may consume it. To do so, this patch adds a new
> init_this_cpu_offset() helper that's called before the usual
> primary/secondary start functions. For consistency, this is also used to
> re-initialize the per-cpu offset after the runtime per-cpu areas have
> been allocated (which can change CPU0's offset).

Is this still early enough now that we have the idreg overrides on the
command-line, which are parsed from C code?

Will