Commit-ID: e365c9df2f2f001450decf9512412d2d5bd1cdef Gitweb: http://git.kernel.org/tip/e365c9df2f2f001450decf9512412d2d5bd1cdef Author: Fenghua Yu <fenghua.yu@xxxxxxxxx> AuthorDate: Tue, 17 May 2011 15:29:14 -0700 Committer: H. Peter Anvin <hpa@xxxxxxxxxxxxxxx> CommitDate: Tue, 17 May 2011 15:40:27 -0700 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@xxxxxxxxx> Link: http://lkml.kernel.org/r/1305671358-14478-6-git-send-email-fenghua.yu@xxxxxxxxx Signed-off-by: H. Peter Anvin <hpa@xxxxxxxxxxxxxxx> --- arch/x86/lib/clear_page_64.S | 33 ++++++++++++++++++++++++--------- 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 aa4326b..f2145cf 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 -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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