From 954e482bde20b0e208fd4d34ef26e10afd194600 Mon Sep 17 00:00:00 2001 From: Fenghua Yu Date: Thu, 24 May 2012 18:19:45 -0700 Subject: [PATCH] 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 Link: http://lkml.kernel.org/r/1337908785-14015-1-git-send-email-fenghua.yu@intel.com Signed-off-by: H. Peter Anvin --- arch/x86/include/asm/alternative.h | 74 ++++++++++++++++++++++++------ arch/x86/include/asm/uaccess_64.h | 11 ++++- arch/x86/kernel/x8664_ksyms_64.c | 1 + 3 files changed, 70 insertions(+), 16 deletions(-) diff --git a/arch/x86/include/asm/alternative.h b/arch/x86/include/asm/alternative.h index 49331bedc158..70780689599a 100644 --- a/arch/x86/include/asm/alternative.h +++ b/arch/x86/include/asm/alternative.h @@ -75,23 +75,54 @@ static inline int alternatives_text_reserved(void *start, void *end) } #endif /* CONFIG_SMP */ +#define OLDINSTR(oldinstr) "661:\n\t" oldinstr "\n662:\n" + +#define b_replacement(number) "663"#number +#define e_replacement(number) "664"#number + +#define alt_slen "662b-661b" +#define alt_rlen(number) e_replacement(number)"f-"b_replacement(number)"f" + +#define ALTINSTR_ENTRY(feature, number) \ + " .long 661b - .\n" /* label */ \ + " .long " b_replacement(number)"f - .\n" /* new instruction */ \ + " .word " __stringify(feature) "\n" /* feature bit */ \ + " .byte " alt_slen "\n" /* source len */ \ + " .byte " alt_rlen(number) "\n" /* replacement len */ + +#define DISCARD_ENTRY(number) /* rlen <= slen */ \ + " .byte 0xff + (" alt_rlen(number) ") - (" alt_slen ")\n" + +#define ALTINSTR_REPLACEMENT(newinstr, feature, number) /* replacement */ \ + b_replacement(number)":\n\t" newinstr "\n" e_replacement(number) ":\n\t" + /* alternative assembly primitive: */ #define ALTERNATIVE(oldinstr, newinstr, feature) \ - \ - "661:\n\t" oldinstr "\n662:\n" \ - ".section .altinstructions,\"a\"\n" \ - " .long 661b - .\n" /* label */ \ - " .long 663f - .\n" /* new instruction */ \ - " .word " __stringify(feature) "\n" /* feature bit */ \ - " .byte 662b-661b\n" /* sourcelen */ \ - " .byte 664f-663f\n" /* replacementlen */ \ - ".previous\n" \ - ".section .discard,\"aw\",@progbits\n" \ - " .byte 0xff + (664f-663f) - (662b-661b)\n" /* rlen <= slen */ \ - ".previous\n" \ - ".section .altinstr_replacement, \"ax\"\n" \ - "663:\n\t" newinstr "\n664:\n" /* replacement */ \ - ".previous" + OLDINSTR(oldinstr) \ + ".section .altinstructions,\"a\"\n" \ + ALTINSTR_ENTRY(feature, 1) \ + ".previous\n" \ + ".section .discard,\"aw\",@progbits\n" \ + DISCARD_ENTRY(1) \ + ".previous\n" \ + ".section .altinstr_replacement, \"ax\"\n" \ + ALTINSTR_REPLACEMENT(newinstr, feature, 1) \ + ".previous" + +#define ALTERNATIVE_2(oldinstr, newinstr1, feature1, newinstr2, feature2)\ + OLDINSTR(oldinstr) \ + ".section .altinstructions,\"a\"\n" \ + ALTINSTR_ENTRY(feature1, 1) \ + ALTINSTR_ENTRY(feature2, 2) \ + ".previous\n" \ + ".section .discard,\"aw\",@progbits\n" \ + DISCARD_ENTRY(1) \ + DISCARD_ENTRY(2) \ + ".previous\n" \ + ".section .altinstr_replacement, \"ax\"\n" \ + ALTINSTR_REPLACEMENT(newinstr1, feature1, 1) \ + ALTINSTR_REPLACEMENT(newinstr2, feature2, 2) \ + ".previous" /* * This must be included *after* the definition of ALTERNATIVE due to @@ -139,6 +170,19 @@ static inline int alternatives_text_reserved(void *start, void *end) asm volatile (ALTERNATIVE("call %P[old]", "call %P[new]", feature) \ : output : [old] "i" (oldfunc), [new] "i" (newfunc), ## input) +/* + * Like alternative_call, but there are two features and respective functions. + * If CPU has feature2, function2 is used. + * Otherwise, if CPU has feature1, function1 is used. + * Otherwise, old function is used. + */ +#define alternative_call_2(oldfunc, newfunc1, feature1, newfunc2, feature2, \ + output, input...) \ + asm volatile (ALTERNATIVE_2("call %P[old]", "call %P[new1]", feature1,\ + "call %P[new2]", feature2) \ + : output : [old] "i" (oldfunc), [new1] "i" (newfunc1), \ + [new2] "i" (newfunc2), ## input) + /* * use this macro(s) if you need more than one output parameter * in alternative_io 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) diff --git a/arch/x86/kernel/x8664_ksyms_64.c b/arch/x86/kernel/x8664_ksyms_64.c index 9796c2f3d074..6020f6f5927c 100644 --- a/arch/x86/kernel/x8664_ksyms_64.c +++ b/arch/x86/kernel/x8664_ksyms_64.c @@ -28,6 +28,7 @@ EXPORT_SYMBOL(__put_user_8); EXPORT_SYMBOL(copy_user_generic_string); EXPORT_SYMBOL(copy_user_generic_unrolled); +EXPORT_SYMBOL(copy_user_enhanced_fast_string); EXPORT_SYMBOL(__copy_user_nocache); EXPORT_SYMBOL(_copy_from_user); EXPORT_SYMBOL(_copy_to_user);