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    Subject[PATCH 03/10] x86/asm: Tweak the comment about wmb() use for IO
    Date
    From: "Michael S. Tsirkin" <mst@redhat.com>

    On x86, we *do* still use the non-nop rmb()/wmb() for IO barriers, but
    even that is generally questionable.

    Leave them around for historical reasons, unless somebody can point to a
    case where they care about the performance. Tweak the comment so people
    don't think they are strictly required in all cases.

    Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
    Cc: Andrey Konovalov <andreyknvl@google.com>
    Cc: Andy Lutomirski <luto@kernel.org>
    Cc: Arnd Bergmann <arnd@arndb.de>
    Cc: Davidlohr Bueso <dave@stgolabs.net>
    Cc: "H. Peter Anvin" <hpa@zytor.com>
    Cc: Ingo Molnar <mingo@kernel.org>
    Cc: Linus Torvalds <torvalds@linux-foundation.org>
    Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Cc: virtualization <virtualization@lists.linux-foundation.org>
    Link: http://lkml.kernel.org/r/1452715911-12067-4-git-send-email-mst@redhat.com
    Signed-off-by: Borislav Petkov <bp@suse.de>
    ---
    arch/x86/include/asm/barrier.h | 4 ++--
    1 file changed, 2 insertions(+), 2 deletions(-)

    diff --git a/arch/x86/include/asm/barrier.h b/arch/x86/include/asm/barrier.h
    index d2aa66a3a4b5..4f95b2affd88 100644
    --- a/arch/x86/include/asm/barrier.h
    +++ b/arch/x86/include/asm/barrier.h
    @@ -6,8 +6,8 @@

    /*
    * Force strict CPU ordering.
    - * And yes, this is required on UP too when we're talking
    - * to devices.
    + *
    + * And yes, this might be required on UP too when we're talking to devices.
    */

    #ifdef CONFIG_X86_32
    --
    2.3.5
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