[RFC PATCH] powerpc/64/ftrace: mprofile-kernel patch out mflr

[Naveen N. Rao]

Hi Nick,

Nicholas Piggin wrote:
> The new mprofile-kernel mcount sequence is
> 
>   mflr	r0
>   bl	_mcount
> 
> Dynamic ftrace patches the branch instruction with a noop, but leaves
> the mflr. mflr is executed by the branch unit that can only execute one
> per cycle on POWER9 and shared with branches, so it would be nice to
> avoid it where possible.
> 
> This patch is a hacky proof of concept to nop out the mflr. Can we do
> this or are there races or other issues with it?

Thanks for implementing this. I don't see a problem with this.

- Naveen