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Date:   Sun, 23 Aug 2020 13:31:03 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Arvind Sankar' <>,
        Miguel Ojeda <>
CC:     Sedat Dilek <>,
        Segher Boessenkool <>,
        Thomas Gleixner <>,
        "Nick Desaulniers" <>,
        "Paul E. McKenney" <>,
        Ingo Molnar <>, Arnd Bergmann <>,
        Borislav Petkov <>,
        "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <>,
        "H. Peter Anvin" <>,
        "Kirill A. Shutemov" <>,
        Zhenzhong Duan <>,
        Kees Cook <>,
        "Peter Zijlstra" <>,
        Juergen Gross <>,
        "Andy Lutomirski" <>,
        Andrew Cooper <>,
        LKML <>,
        clang-built-linux <>,
        Will Deacon <>,
        "Linus Torvalds" <>
Subject: RE: [PATCH] x86: work around clang IAS bug referencing __force_order

From: Arvind Sankar
> Sent: 22 August 2020 22:17
> Assuming we don't want to risk removing force_order, I'd suggest
> - make it an input/output operand, so it enforces ordering fully.
> - either restrict it to gcc < 8, or just provide a proper definition in
>   some file (maybe arch/x86/kernel/cpu/common.c)?

Is it possible to replace __force_order with a symbol that the
linker scripts defines?
Or just define __force_order in the linker script to some
'random' constant (eg 0).

ISTM that adding "m"(__force_order) to asm volatile can do no harm.
Especially for accesses to CRn and MSRn (etc) which might have obscure
side effects.


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