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

[tip-bot for Ingo Molnar]

Commit-ID:  99770737ca7e3ebc14e66460a69b7032de9421e1
Gitweb:     http://git.kernel.org/tip/99770737ca7e3ebc14e66460a69b7032de9421e1
Author:     Ingo Molnar <mingo@xxxxxxxxxx>
AuthorDate: Fri, 21 Aug 2015 08:33:53 +0200
Committer:  Ingo Molnar <mingo@xxxxxxxxxx>
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@xxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Brian Gerst <brgerst@xxxxxxxxx>
Cc: Denys Vlasenko <dvlasenk@xxxxxxxxxx>
Cc: H. Peter Anvin <hpa@xxxxxxxxx>
Cc: Huang Rui <ray.huang@xxxxxxx>
Cc: John Stultz <john.stultz@xxxxxxxxxx>
Cc: Len Brown <lenb@xxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Ralf Baechle <ralf@xxxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: kvm ML <kvm@xxxxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/dddbf98a2af53312e9aa73a5a2b1622fe5d6f52b.1434501121.git.luto@xxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
 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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