[PATCH v2] arm64: fix bug for reloading FPSIMD state after cpu power off

[Will Deacon]

On Mon, Sep 01, 2014 at 10:34:28AM +0100, Catalin Marinas wrote:
> On Mon, Sep 01, 2014 at 04:09:51AM +0100, Leo Yan wrote:
> > Now arm64 defers reloading FPSIMD state, but this optimization also
> > introduces the bug after cpu resume back from low power mode.
> > 
> > The reason is after the cpu has been powered off, s/w need set the
> > cpu's fpsimd_last_state to NULL so that it will force to reload
> > FPSIMD state for the thread, otherwise there has the chance to meet
> > the condition for both the task's fpsimd_state.cpu field contains the
> > id of the current cpu, and the cpu's fpsimd_last_state per-cpu variable
> > points to the task's fpsimd_state, so finally kernel will skip to reload
> > the context during it return back to userland.
> > 
> > Signed-off-by: Leo Yan <leoy at marvell.com>
> 
> Reviewed-by: Catalin Marinas <catalin.marinas at arm.com>
> 
> (and cc'ing Will to pick it up since he's handling the 3.17 release)

Cheers for the CC; applied to fixes/core (I'll push out once I've run the
regression tests).

I aim to tag that branch tonight if we don't get any more fixes today.

Will