Merge tag 'alternatives_padding' of git://git.kernel.org/pub/scm/linux/kernel/git/bp/bp into x86/asm

Pull alternative instructions framework improvements from Borislav Petkov:

 "A more involved rework of the alternatives framework to be able to
  pad instructions and thus make using the alternatives macros more
  straightforward and without having to figure out old and new instruction
  sizes but have the toolchain figure that out for us.

  Furthermore, it optimizes JMPs used so that fetch and decode can be
  relieved with smaller versions of the JMPs, where possible.

  Some stats:

    x86_64 defconfig:

    Alternatives sites total:               2478
    Total padding added (in Bytes):         6051

  The padding is currently done for:

    X86_FEATURE_ALWAYS
    X86_FEATURE_ERMS
    X86_FEATURE_LFENCE_RDTSC
    X86_FEATURE_MFENCE_RDTSC
    X86_FEATURE_SMAP

  This is with the latest version of the patchset. Of course, on each
  machine the alternatives sites actually being patched are a proper
  subset of the total number."

Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 2 insertions, 4 deletions

diff --git a/arch/x86/include/asm/barrier.h b/arch/x86/include/asm/barrier.h
index 2ab1eb33106e..959e45b81fe2 100644
--- a/arch/x86/include/asm/barrier.h
+++ b/arch/x86/include/asm/barrier.h
@@ -95,13 +95,11 @@ do {									\
  * Stop RDTSC speculation. This is needed when you need to use RDTSC
  * (or get_cycles or vread that possibly accesses the TSC) in a defined
  * code region.
- *
- * (Could use an alternative three way for this if there was one.)
  */
 static __always_inline void rdtsc_barrier(void)
 {
-        alternative(ASM_NOP3, "mfence", X86_FEATURE_MFENCE_RDTSC);
-        alternative(ASM_NOP3, "lfence", X86_FEATURE_LFENCE_RDTSC);
+        alternative_2("", "mfence", X86_FEATURE_MFENCE_RDTSC,
+                          "lfence", X86_FEATURE_LFENCE_RDTSC);
 }
 
 #endif /* _ASM_X86_BARRIER_H */