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Date:   Mon, 6 Jul 2020 11:39:33 -0700
From:   "Paul E. McKenney" <>
To:     Peter Zijlstra <>
Cc:     Marco Elver <>,
        Nick Desaulniers <>,
        Sami Tolvanen <>,
        Masahiro Yamada <>,
        Will Deacon <>,
        Greg Kroah-Hartman <>,
        Kees Cook <>,
        clang-built-linux <>,
        Kernel Hardening <>,
        linux-arch <>,
        Linux ARM <>,
        Linux Kbuild mailing list <>,
        LKML <>,,
        "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <>
Subject: Re: [PATCH 00/22] add support for Clang LTO

On Mon, Jul 06, 2020 at 08:29:26PM +0200, Peter Zijlstra wrote:
> On Mon, Jul 06, 2020 at 09:26:33AM -0700, Paul E. McKenney wrote:
> > And perhaps more constructively, we do need to prioritize address and data
> > dependencies over control dependencies.  For one thing, there are a lot
> > more address/data dependencies in existing code than there are control
> > dependencies, and (sadly, perhaps more importantly) there are a lot more
> > people who are convinced that address/data dependencies are important.
> If they do not consider their Linux OS running correctly :-)

Many of them really do not care at all.  In fact, some would consider
Linux failing to run as an added bonus.

> > For another (admittedly more theoretical) thing, the OOTA scenarios
> > stemming from control dependencies are a lot less annoying than those
> > from address/data dependencies.
> > 
> > And address/data dependencies are as far as I know vulnerable to things
> > like conditional-move instructions that can cause problems for control
> > dependencies.
> > 
> > Nevertheless, yes, control dependencies also need attention.
> Today I added one more \o/

Just make sure you continually check to make sure that compilers
don't break it, along with the others you have added.  ;-)

							Thanx, Paul

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