linux-kernel - Re: [PATCH 01/25] x86: Make SMAP 64-bit only

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Date:   Mon, 18 Mar 2019 18:51:35 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Thomas Gleixner <tglx@...utronix.de>, Peter Anvin <hpa@...or.com>,
        Julien Thierry <julien.thierry@....com>,
        Will Deacon <will.deacon@....com>,
        Andy Lutomirski <luto@...capital.net>,
        Ingo Molnar <mingo@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        James Morse <james.morse@....com>, valentin.schneider@....com,
        Brian Gerst <brgerst@...il.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Andrew Lutomirski <luto@...nel.org>,
        Borislav Petkov <bp@...en8.de>,
        Denys Vlasenko <dvlasenk@...hat.com>,
        Linux List Kernel Mailing <linux-kernel@...r.kernel.org>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [PATCH 01/25] x86: Make SMAP 64-bit only

On Mon, Mar 18, 2019 at 06:36:57PM +0100, Peter Zijlstra wrote:
> then I'd sleep much better if we make 32bit context switch EFLAGS.
> Because, yes, x86_64 objtool validates a lot of the x86_32 code too, but
> unless we have 100% coverage, there's always the chance an AC=1 escapes.

How about I do a patch that schedules EFLAGS for both 32bit and 64bit,
mark this for backporting to infinity.

And then at the end, after the objtool-ac bits land, I do a patch
removing the EFLAGS scheduling for x86_64.