[GIT PULL] x86/asm changes for v4.13

[Ingo Molnar]

Linus,

Please pull the latest x86-asm-for-linus git tree from:

   git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git x86-asm-for-linus

   # HEAD: 236222d39347e0e486010f10c1493e83dbbdfba8 x86/uaccess: Optimize 
copy_user_enhanced_fast_string() for short strings

A single commit micro-optimizing short string copies on certain Intel CPUs.

 Thanks,

        Ingo

------------------>
Paolo Abeni (1):
      x86/uaccess: Optimize copy_user_enhanced_fast_string() for short strings


 arch/x86/lib/copy_user_64.S | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/arch/x86/lib/copy_user_64.S b/arch/x86/lib/copy_user_64.S
index c5959576c315..020f75cc8cf6 100644
--- a/arch/x86/lib/copy_user_64.S
+++ b/arch/x86/lib/copy_user_64.S
@@ -37,7 +37,7 @@ ENTRY(copy_user_generic_unrolled)
        movl %edx,%ecx
        andl $63,%edx
        shrl $6,%ecx
-       jz 17f
+       jz .L_copy_short_string
 1:     movq (%rsi),%r8
 2:     movq 1*8(%rsi),%r9
 3:     movq 2*8(%rsi),%r10
@@ -58,7 +58,8 @@ ENTRY(copy_user_generic_unrolled)
        leaq 64(%rdi),%rdi
        decl %ecx
        jnz 1b
-17:    movl %edx,%ecx
+.L_copy_short_string:
+       movl %edx,%ecx
        andl $7,%edx
        shrl $3,%ecx
        jz 20f
@@ -174,6 +175,8 @@ EXPORT_SYMBOL(copy_user_generic_string)
  */
 ENTRY(copy_user_enhanced_fast_string)
        ASM_STAC
+       cmpl $64,%edx
+       jb .L_copy_short_string /* less then 64 bytes, avoid the costly 'rep' */
        movl %edx,%ecx
 1:     rep
        movsb