[tip:x86/asm] x86/asm/tsc: Add rdtscll() merge helper

tip-bot for Ingo Molnar
2015-08-21T07:46:46Z

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);