#include <linux/linkage.h>
#include <asm/cpufeatures.h>
#include <asm/alternative-asm.h>
#include <asm/export.h>
/*
* Most CPUs support enhanced REP MOVSB/STOSB instructions. It is
* recommended to use this when possible and we do use them by default.
* If enhanced REP MOVSB/STOSB is not available, try to use fast string.
* Otherwise, use original.
*/
/*
* Zero a page.
* %rdi - page
*/
ENTRY(clear_page)
ALTERNATIVE_2 "jmp clear_page_orig", "", X86_FEATURE_REP_GOOD, \
"jmp clear_page_c_e", X86_FEATURE_ERMS
movl $4096/8,%ecx
xorl %eax,%eax
rep stosq
ret
ENDPROC(clear_page)
EXPORT_SYMBOL(clear_page)
ENTRY(clear_page_orig)
xorl %eax,%eax
movl $4096/64,%ecx
.p2align 4
.Lloop:
decl %ecx
#define PUT(x) movq %rax,x*8(%rdi)
movq %rax,(%rdi)
PUT(1)
PUT(2)
PUT(3)
PUT(4)
PUT(5)
PUT(6)
PUT(7)
leaq 64(%rdi),%rdi
jnz .Lloop
nop
ret
ENDPROC(clear_page_orig)
ENTRY(clear_page_c_e)
movl $4096,%ecx
xorl %eax,%eax
rep stosb
ret
ENDPROC(clear_page_c_e)
