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>
diff --git a/arch/x86/include/asm/alternative.h b/arch/x86/include/asm/alternative.h
index 49331be..7078068 100644
--- a/arch/x86/include/asm/alternative.h
+++ b/arch/x86/include/asm/alternative.h
@@ -75,23 +75,54 @@
}
#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
@@ -140,6 +171,19 @@
: 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
*/