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Message-ID: <1491181311.26047.23.camel@kernel.crashing.org>
Subject: Re: [PATCH] powerpc: Add POWER9 copy_page() loop
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Anton Blanchard <anton@samba.org>, Nicholas Piggin <npiggin@gmail.com>
Cc: paulus@samba.org, mpe@ellerman.id.au, linuxppc-dev@lists.ozlabs.org
Date: Mon, 03 Apr 2017 11:01:51 +1000
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On Mon, 2017-04-03 at 10:54 +1000, Anton Blanchard wrote:
> > > Good idea, I hadn't thought of embedding it all in a feature
> > > section.  
> > 
> > It may not work currently because you get those ftr_alt_97 relocation
> > errors with the "else" parts because relative branches to other code
> > need to be direct and I think reachable from both places.
> 
> I thought about this a bit more. One potential issue will be
> profiling - perf annotate will match the samples against the unpatched
> code which could be very confusing.

Could we make all those functions a dynamic-linker style stub ?

IE, they "find" the right target function and call a helper to patch
the calling site to call directly into the right one on the first
call.

Cheers,
Ben.