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    Subject[tip:x86/asm] x86/asm/tsc: Add rdtscll() merge helper
    Commit-ID:  99770737ca7e3ebc14e66460a69b7032de9421e1
    Gitweb: http://git.kernel.org/tip/99770737ca7e3ebc14e66460a69b7032de9421e1
    Author: Ingo Molnar <mingo@kernel.org>
    AuthorDate: Fri, 21 Aug 2015 08:33:53 +0200
    Committer: Ingo Molnar <mingo@kernel.org>
    CommitDate: Fri, 21 Aug 2015 08:35:42 +0200

    x86/asm/tsc: Add rdtscll() merge helper

    Some in-flight code makes use of the old rdtscll() (now removed), provide a wrapper
    for a kernel cycle to smooth the transition to rdtsc().

    ( We use the safest variant, rdtsc_ordered(), which has barriers - this adds another
    incentive to remove the wrapper in the future. )

    Cc: Andy Lutomirski <luto@kernel.org>
    Cc: Borislav Petkov <bp@suse.de>
    Cc: Andy Lutomirski <luto@amacapital.net>
    Cc: Borislav Petkov <bp@alien8.de>
    Cc: Brian Gerst <brgerst@gmail.com>
    Cc: Denys Vlasenko <dvlasenk@redhat.com>
    Cc: H. Peter Anvin <hpa@zytor.com>
    Cc: Huang Rui <ray.huang@amd.com>
    Cc: John Stultz <john.stultz@linaro.org>
    Cc: Len Brown <lenb@kernel.org>
    Cc: Linus Torvalds <torvalds@linux-foundation.org>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Ralf Baechle <ralf@linux-mips.org>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Cc: kvm ML <kvm@vger.kernel.org>
    Link: http://lkml.kernel.org/r/dddbf98a2af53312e9aa73a5a2b1622fe5d6f52b.1434501121.git.luto@kernel.org
    Signed-off-by: Ingo Molnar <mingo@kernel.org>
    ---
    arch/x86/include/asm/msr.h | 3 +++
    1 file changed, 3 insertions(+)

    diff --git a/arch/x86/include/asm/msr.h b/arch/x86/include/asm/msr.h
    index 131eec2..54e9f08 100644
    --- a/arch/x86/include/asm/msr.h
    +++ b/arch/x86/include/asm/msr.h
    @@ -152,6 +152,9 @@ static __always_inline unsigned long long rdtsc_ordered(void)
    return rdtsc();
    }

    +/* Deprecated, keep it for a cycle for easier merging: */
    +#define rdtscll(now) do { (now) = rdtsc_ordered(); } while (0)
    +
    static inline unsigned long long native_read_pmc(int counter)
    {
    DECLARE_ARGS(val, low, high);

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