Re: [PATCH 08/12] powerpc/ftrace: Rework ftrace_caller()

From: Torsten Duwe
Date: Thu Feb 25 2016 - 09:26:01 EST

On Thu, Feb 25, 2016 at 01:28:31AM +1100, Michael Ellerman wrote:
> The main change is to just use paca->kernel_toc, rather than a branch to
> +4 and mflr etc. That makes the code simpler and should also perform
> better.


> There was also a sequence after ftrace_call() where we load from
> pt_regs->nip, move to LR, then a few instructions later load from LRSAVE
> and move to LR. Instead I think we want to put pt_regs->nip into CTR and
> branch to it later.

Yes, I did some of this cleanup in the livepatch implementation.

> We also rework some of the SPR loads to hopefully speed them up a bit.
> Also comment the asm much more, to hopefully make it clearer.
> Signed-off-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx>

Reviewed-by: Torsten Duwe <duwe@xxxxxxx>