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| author |   Fenghua Yu <fenghua.yu@intel.com> | 2012-05-24 18:19:45 -0700 |
|---|---|---|
| committer |   H. Peter Anvin <hpa@linux.intel.com> | 2012-06-29 15:33:34 -0700 |
| commit | 954e482bde20b0e208fd4d34ef26e10afd194600 (patch) | |
| tree | a98702fdde1d47b31851cee7b81849dec8b91f09 /arch/x86/include/asm/uaccess_64.h | |
| parent | x86/alternatives: Use atomic_xchg() instead atomic_dec_and_test() for stop_machine_text_poke() (diff) | |
| download | linux-dev-954e482bde20b0e208fd4d34ef26e10afd194600.tar.xz linux-dev-954e482bde20b0e208fd4d34ef26e10afd194600.zip | |
x86/copy_user_generic: Optimize copy_user_generic with CPU erms feature
According to Intel 64 and IA-32 SDM and Optimization Reference Manual, beginning
with Ivybridge, REG string operation using MOVSB and STOSB can provide both
flexible and high-performance REG string operations in cases like memory copy.
Enhancement availability is indicated by CPUID.7.0.EBX[9] (Enhanced REP MOVSB/
STOSB).
If CPU erms feature is detected, patch copy_user_generic with enhanced fast
string version of copy_user_generic.
A few new macros are defined to reduce duplicate code in ALTERNATIVE and
ALTERNATIVE_2.
Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
Link: http://lkml.kernel.org/r/1337908785-14015-1-git-send-email-fenghua.yu@intel.com
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Diffstat (limited to 'arch/x86/include/asm/uaccess_64.h')
| -rw-r--r-- | arch/x86/include/asm/uaccess_64.h | 11 |
1 files changed, 10 insertions, 1 deletions
diff --git a/arch/x86/include/asm/uaccess_64.h b/arch/x86/include/asm/uaccess_64.h index 8e796fbbf9c6..d8def8b3dba0 100644 --- a/arch/x86/include/asm/uaccess_64.h +++ b/arch/x86/include/asm/uaccess_64.h @@ -17,6 +17,8 @@ /* Handles exceptions in both to and from, but doesn't do access_ok */ __must_check unsigned long +copy_user_enhanced_fast_string(void *to, const void *from, unsigned len); +__must_check unsigned long copy_user_generic_string(void *to, const void *from, unsigned len); __must_check unsigned long copy_user_generic_unrolled(void *to, const void *from, unsigned len); @@ -26,9 +28,16 @@ copy_user_generic(void *to, const void *from, unsigned len) { unsigned ret; - alternative_call(copy_user_generic_unrolled, + /* + * If CPU has ERMS feature, use copy_user_enhanced_fast_string. + * Otherwise, if CPU has rep_good feature, use copy_user_generic_string. + * Otherwise, use copy_user_generic_unrolled. + */ + alternative_call_2(copy_user_generic_unrolled, copy_user_generic_string, X86_FEATURE_REP_GOOD, + copy_user_enhanced_fast_string, + X86_FEATURE_ERMS, ASM_OUTPUT2("=a" (ret), "=D" (to), "=S" (from), "=d" (len)), "1" (to), "2" (from), "3" (len) |