[PATCH] x86_64: Undo the earlier changes to remove unrolled copy/memset functions

They cause quite bad performance regressions on Netburst
This is temporary until we can get new optimized functions
for these CPUs.

This undoes changes that were done in 2.6.15 and in 2.6.16-rc1,
essentially bringing the code back to 2.6.14 level. Only change
is I renamed the X86_FEATURE_K8_C flag to X86_FEATURE_REP_GOOD
and fixed the check for the flag and also fixed some comments.

Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 226 insertions, 21 deletions

diff --git a/arch/x86_64/lib/copy_user.S b/arch/x86_64/lib/copy_user.S
index 79422b6559c3..f64569b83b54 100644
--- a/arch/x86_64/lib/copy_user.S
+++ b/arch/x86_64/lib/copy_user.S
@@ -4,9 +4,12 @@
  * Functions to copy from and to user space.            
  */              
 
+#define FIX_ALIGNMENT 1
+
         #include <asm/current.h>
         #include <asm/asm-offsets.h>
         #include <asm/thread_info.h>
+        #include <asm/cpufeature.h>
 
 /* Standard copy_to_user with segment limit checking */         
         .globl copy_to_user
@@ -18,7 +21,23 @@ copy_to_user:
         jc  bad_to_user
         cmpq threadinfo_addr_limit(%rax),%rcx
         jae bad_to_user
-        jmp copy_user_generic
+2:
+        .byte 0xe9      /* 32bit jump */
+        .long .Lcug-1f
+1:
+
+        .section .altinstr_replacement,"ax"
+3:      .byte 0xe9                      /* replacement jmp with 8 bit immediate */
+        .long copy_user_generic_c-1b    /* offset */
+        .previous
+        .section .altinstructions,"a"
+        .align 8
+        .quad  2b
+        .quad  3b
+        .byte  X86_FEATURE_REP_GOOD
+        .byte  5
+        .byte  5
+        .previous
 
 /* Standard copy_from_user with segment limit checking */       
         .globl copy_from_user
@@ -53,44 +72,230 @@ bad_to_user:
  * rsi source
  * rdx count
  *
- * Only 4GB of copy is supported. This shouldn't be a problem
- * because the kernel normally only writes from/to page sized chunks
- * even if user space passed a longer buffer.
- * And more would be dangerous because both Intel and AMD have
- * errata with rep movsq > 4GB. If someone feels the need to fix
- * this please consider this.
- *
  * Output:              
  * eax uncopied bytes or 0 if successful.
  */
-
         .globl copy_user_generic
+        .p2align 4
 copy_user_generic:
+        .byte 0x66,0x66,0x90    /* 5 byte nop for replacement jump */
+        .byte 0x66,0x90
+1:
+        .section .altinstr_replacement,"ax"
+2:      .byte 0xe9                   /* near jump with 32bit immediate */
+        .long copy_user_generic_c-1b /* offset */
+        .previous
+        .section .altinstructions,"a"
+        .align 8
+        .quad  copy_user_generic
+        .quad  2b
+        .byte  X86_FEATURE_REP_GOOD
+        .byte  5
+        .byte  5
+        .previous
+.Lcug:
+        pushq %rbx
+        xorl %eax,%eax          /*zero for the exception handler */
+
+#ifdef FIX_ALIGNMENT
+        /* check for bad alignment of destination */
+        movl %edi,%ecx
+        andl $7,%ecx
+        jnz  .Lbad_alignment
+.Lafter_bad_alignment:
+#endif
+
+        movq %rdx,%rcx
+
+        movl $64,%ebx
+        shrq $6,%rdx
+        decq %rdx
+        js   .Lhandle_tail
+
+        .p2align 4
+.Lloop:
+.Ls1:   movq (%rsi),%r11
+.Ls2:   movq 1*8(%rsi),%r8
+.Ls3:   movq 2*8(%rsi),%r9
+.Ls4:   movq 3*8(%rsi),%r10
+.Ld1:   movq %r11,(%rdi)
+.Ld2:   movq %r8,1*8(%rdi)
+.Ld3:   movq %r9,2*8(%rdi)
+.Ld4:   movq %r10,3*8(%rdi)
+
+.Ls5:   movq 4*8(%rsi),%r11
+.Ls6:   movq 5*8(%rsi),%r8
+.Ls7:   movq 6*8(%rsi),%r9
+.Ls8:   movq 7*8(%rsi),%r10
+.Ld5:   movq %r11,4*8(%rdi)
+.Ld6:   movq %r8,5*8(%rdi)
+.Ld7:   movq %r9,6*8(%rdi)
+.Ld8:   movq %r10,7*8(%rdi)
+
+        decq %rdx
+
+        leaq 64(%rsi),%rsi
+        leaq 64(%rdi),%rdi
+
+        jns  .Lloop
+
+        .p2align 4
+.Lhandle_tail:
+        movl %ecx,%edx
+        andl $63,%ecx
+        shrl $3,%ecx
+        jz   .Lhandle_7
+        movl $8,%ebx
+        .p2align 4
+.Lloop_8:
+.Ls9:   movq (%rsi),%r8
+.Ld9:   movq %r8,(%rdi)
+        decl %ecx
+        leaq 8(%rdi),%rdi
+        leaq 8(%rsi),%rsi
+        jnz .Lloop_8
+
+.Lhandle_7:
+        movl %edx,%ecx
+        andl $7,%ecx
+        jz   .Lende
+        .p2align 4
+.Lloop_1:
+.Ls10:  movb (%rsi),%bl
+.Ld10:  movb %bl,(%rdi)
+        incq %rdi
+        incq %rsi
+        decl %ecx
+        jnz .Lloop_1
+
+.Lende:
+        popq %rbx
+        ret
+
+#ifdef FIX_ALIGNMENT
+        /* align destination */
+        .p2align 4
+.Lbad_alignment:
+        movl $8,%r9d
+        subl %ecx,%r9d
+        movl %r9d,%ecx
+        cmpq %r9,%rdx
+        jz   .Lhandle_7
+        js   .Lhandle_7
+.Lalign_1:
+.Ls11:  movb (%rsi),%bl
+.Ld11:  movb %bl,(%rdi)
+        incq %rsi
+        incq %rdi
+        decl %ecx
+        jnz .Lalign_1
+        subq %r9,%rdx
+        jmp .Lafter_bad_alignment
+#endif
+
+        /* table sorted by exception address */
+        .section __ex_table,"a"
+        .align 8
+        .quad .Ls1,.Ls1e
+        .quad .Ls2,.Ls2e
+        .quad .Ls3,.Ls3e
+        .quad .Ls4,.Ls4e
+        .quad .Ld1,.Ls1e
+        .quad .Ld2,.Ls2e
+        .quad .Ld3,.Ls3e
+        .quad .Ld4,.Ls4e
+        .quad .Ls5,.Ls5e
+        .quad .Ls6,.Ls6e
+        .quad .Ls7,.Ls7e
+        .quad .Ls8,.Ls8e
+        .quad .Ld5,.Ls5e
+        .quad .Ld6,.Ls6e
+        .quad .Ld7,.Ls7e
+        .quad .Ld8,.Ls8e
+        .quad .Ls9,.Le_quad
+        .quad .Ld9,.Le_quad
+        .quad .Ls10,.Le_byte
+        .quad .Ld10,.Le_byte
+#ifdef FIX_ALIGNMENT
+        .quad .Ls11,.Lzero_rest
+        .quad .Ld11,.Lzero_rest
+#endif
+        .quad .Le5,.Le_zero
+        .previous
+
+        /* compute 64-offset for main loop. 8 bytes accuracy with error on the
+           pessimistic side. this is gross. it would be better to fix the
+           interface. */
+        /* eax: zero, ebx: 64 */
+.Ls1e:  addl $8,%eax
+.Ls2e:  addl $8,%eax
+.Ls3e:  addl $8,%eax
+.Ls4e:  addl $8,%eax
+.Ls5e:  addl $8,%eax
+.Ls6e:  addl $8,%eax
+.Ls7e:  addl $8,%eax
+.Ls8e:  addl $8,%eax
+        addq %rbx,%rdi  /* +64 */
+        subq %rax,%rdi  /* correct destination with computed offset */
+
+        shlq $6,%rdx    /* loop counter * 64 (stride length) */
+        addq %rax,%rdx  /* add offset to loopcnt */
+        andl $63,%ecx   /* remaining bytes */
+        addq %rcx,%rdx  /* add them */
+        jmp .Lzero_rest
+
+        /* exception on quad word loop in tail handling */
+        /* ecx: loopcnt/8, %edx: length, rdi: correct */
+.Le_quad:
+        shll $3,%ecx
+        andl $7,%edx
+        addl %ecx,%edx
+        /* edx: bytes to zero, rdi: dest, eax:zero */
+.Lzero_rest:
+        movq %rdx,%rcx
+.Le_byte:
+        xorl %eax,%eax
+.Le5:   rep
+        stosb
+        /* when there is another exception while zeroing the rest just return */
+.Le_zero:
+        movq %rdx,%rax
+        jmp .Lende
+
+        /* Some CPUs run faster using the string copy instructions.
+           This is also a lot simpler. Use them when possible.
+           Patch in jmps to this code instead of copying it fully
+           to avoid unwanted aliasing in the exception tables. */
+
+ /* rdi destination
+  * rsi source
+  * rdx count
+  *
+  * Output:
+  * eax uncopied bytes or 0 if successfull.
+  *
+  * Only 4GB of copy is supported. This shouldn't be a problem
+  * because the kernel normally only writes from/to page sized chunks
+  * even if user space passed a longer buffer.
+  * And more would be dangerous because both Intel and AMD have
+  * errata with rep movsq > 4GB. If someone feels the need to fix
+  * this please consider this.
+   */
+copy_user_generic_c:
         movl %edx,%ecx
         shrl $3,%ecx
         andl $7,%edx    
-        jz   5f
 1:      rep 
         movsq 
         movl %edx,%ecx
-        xor %eax,%eax
 2:      rep
         movsb
+4:      movl %ecx,%eax
         ret
-        /* align here? */
-5:      xorl %eax,%eax
-6:      rep movsq
-        ret
-
-        .section .fixup,"ax"
 3:      lea (%rdx,%rcx,8),%rax
         ret
-4:      movl %ecx,%eax
-        ret
-        .previous
 
         .section __ex_table,"a"
         .quad 1b,3b
         .quad 2b,4b
-        .quad 6b,4b
         .previous