arch: arm64: Use atomic for fpu_owner pointer
Currently the lazy fpu saving algorithm in arm64 is using the fpu_owner
pointer from the cpu structure to understand the owner of the context
in the cpu and save it in case someone different from the owner is
accessing the fpu.
The semantics for memory consistency across smp systems is quite prone
to errors and reworks on the current code might miss some barriers that
could lead to inconsistent state across cores, so to overcome the issue,
use atomics to hide the complexity and be sure that the code will behave
as intended.
While there, add some isb barriers after writes to cpacr_el1, following
the guidance of ARM ARM specs about writes on system registers.
Signed-off-by: Luca Fancellu <luca.fancellu@arm.com>
2 files changed
