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authorFenghua Yu <fenghua.yu@intel.com>2011-05-17 15:29:14 -0700
committerH. Peter Anvin <hpa@linux.intel.com>2011-05-17 15:40:27 -0700
commite365c9df2f2f001450decf9512412d2d5bd1cdef (patch)
tree3670f466631b7ddeb710f54899020ee4a792edc4 /arch/x86/lib/clear_page_64.S
parent9072d11da15a71e086eab3b5085184f2c1d06913 (diff)
x86, mem: clear_page_64.S: Support clear_page() with enhanced REP MOVSB/STOSB
Intel processors are adding enhancements to REP MOVSB/STOSB and the use of REP MOVSB/STOSB for optimal memcpy/memset or similar functions is recommended. Enhancement availability is indicated by CPUID.7.0.EBX[9] (Enhanced REP MOVSB/ STOSB). Support clear_page() with rep stosb for processor supporting enhanced REP MOVSB /STOSB. On processors supporting enhanced REP MOVSB/STOSB, the alternative clear_page_c_e function using enhanced REP STOSB overrides the original function and the fast string function. Signed-off-by: Fenghua Yu <fenghua.yu@intel.com> Link: http://lkml.kernel.org/r/1305671358-14478-6-git-send-email-fenghua.yu@intel.com Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Diffstat (limited to 'arch/x86/lib/clear_page_64.S')
-rw-r--r--arch/x86/lib/clear_page_64.S33
1 files changed, 24 insertions, 9 deletions
diff --git a/arch/x86/lib/clear_page_64.S b/arch/x86/lib/clear_page_64.S
index aa4326bfb24a..f2145cfa12a6 100644
--- a/arch/x86/lib/clear_page_64.S
+++ b/arch/x86/lib/clear_page_64.S
@@ -1,5 +1,6 @@
#include <linux/linkage.h>
#include <asm/dwarf2.h>
+#include <asm/alternative-asm.h>
/*
* Zero a page.
@@ -14,6 +15,15 @@ ENTRY(clear_page_c)
CFI_ENDPROC
ENDPROC(clear_page_c)
+ENTRY(clear_page_c_e)
+ CFI_STARTPROC
+ movl $4096,%ecx
+ xorl %eax,%eax
+ rep stosb
+ ret
+ CFI_ENDPROC
+ENDPROC(clear_page_c_e)
+
ENTRY(clear_page)
CFI_STARTPROC
xorl %eax,%eax
@@ -38,21 +48,26 @@ ENTRY(clear_page)
.Lclear_page_end:
ENDPROC(clear_page)
- /* Some CPUs run faster using the string instructions.
- It is also a lot simpler. Use this when possible */
+ /*
+ * Some CPUs support enhanced REP MOVSB/STOSB instructions.
+ * It is recommended to use this when possible.
+ * If enhanced REP MOVSB/STOSB is not available, try to use fast string.
+ * Otherwise, use original function.
+ *
+ */
#include <asm/cpufeature.h>
.section .altinstr_replacement,"ax"
1: .byte 0xeb /* jmp <disp8> */
.byte (clear_page_c - clear_page) - (2f - 1b) /* offset */
-2:
+2: .byte 0xeb /* jmp <disp8> */
+ .byte (clear_page_c_e - clear_page) - (3f - 2b) /* offset */
+3:
.previous
.section .altinstructions,"a"
- .align 8
- .quad clear_page
- .quad 1b
- .word X86_FEATURE_REP_GOOD
- .byte .Lclear_page_end - clear_page
- .byte 2b - 1b
+ altinstruction_entry clear_page,1b,X86_FEATURE_REP_GOOD,\
+ .Lclear_page_end-clear_page, 2b-1b
+ altinstruction_entry clear_page,2b,X86_FEATURE_ERMS, \
+ .Lclear_page_end-clear_page,3b-2b
.previous