Re: [PATCH v3 5/6] x86/ftrace: Use text_poke()

[Josh Poimboeuf]

On Wed, Oct 16, 2019 at 09:42:17AM +0200, Peter Zijlstra wrote:
> > which are not compatible with livepatching. GCC upstream now has
> > -flive-patching option, which disables all those interfering optimizations.
> 
> Which, IIRC, has a significant performance impact and should thus really
> not be used...
> 
> If distros ship that crap, I'm going to laugh at them the next time they
> want a single digit performance improvement because *important*.

I have a crazy plan to try to use objtool to detect function changes at
a binary level, which would hopefully allow us to drop this flag.

But regardless, I wonder if we enabled this flag prematurely.  We still
don't have a reasonable way to use it for creating source-based live
patches upstream, and it should really be optional for CONFIG_LIVEPATCH,
since kpatch-build doesn't need it.

-- 
Josh