[Xen-changelog] [xen-unstable] x86: streamline page fault path

[Xen patchbot-unstable <patchbot@xxxxxxx>]

# HG changeset patch
# User Jan Beulich <jbeulich@xxxxxxxxxx>
# Date 1309549435 -3600
# Node ID 1b9cce28cab754b8cc0a7951e15a34768c90402e
# Parent  3261d198c3aa573ff7e8370b9787b72ba5dfa38a
x86: streamline page fault path

#PF is, in all "normal" usage models, the only potentially high
frequency (and hence performance sensitive) exception. Thus make it
the fall-through case into handle_exception (rather than
divide_error for x86-32 and not having one at all for x86-64).

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxxxx>
---


diff -r 3261d198c3aa -r 1b9cce28cab7 xen/arch/x86/x86_32/entry.S
--- a/xen/arch/x86/x86_32/entry.S       Fri Jul 01 20:43:02 2011 +0100
+++ b/xen/arch/x86/x86_32/entry.S       Fri Jul 01 20:43:55 2011 +0100
@@ -426,9 +426,8 @@
         jnz   test_all_events
         jmp   restore_all_xen
 
-ENTRY(divide_error)
-        pushl $TRAP_divide_error<<16
-        ALIGN
+ENTRY(page_fault)
+        movw  $TRAP_page_fault,2(%esp)
 handle_exception:
         FIXUP_RING0_GUEST_STACK
         SAVE_ALL(1f,2f)
@@ -501,6 +500,10 @@
         pushl $TRAP_no_device<<16
         jmp   handle_exception
 
+ENTRY(divide_error)
+        pushl $TRAP_divide_error<<16
+        jmp   handle_exception
+
 ENTRY(debug)
         pushl $TRAP_debug<<16
         jmp   handle_exception
@@ -545,10 +548,6 @@
         movw  $TRAP_alignment_check,2(%esp)
         jmp   handle_exception
 
-ENTRY(page_fault)
-        movw  $TRAP_page_fault,2(%esp)
-        jmp   handle_exception
-
 ENTRY(spurious_interrupt_bug)
         pushl $TRAP_spurious_int<<16
         jmp   handle_exception
diff -r 3261d198c3aa -r 1b9cce28cab7 xen/arch/x86/x86_64/entry.S
--- a/xen/arch/x86/x86_64/entry.S       Fri Jul 01 20:43:02 2011 +0100
+++ b/xen/arch/x86/x86_64/entry.S       Fri Jul 01 20:43:55 2011 +0100
@@ -461,9 +461,11 @@
         jz    test_all_events
         jmp   compat_test_all_events
 
-        ALIGN
+ENTRY(page_fault)
+        movl  $TRAP_page_fault,4(%rsp)
 /* No special register assumptions. */
-ENTRY(handle_exception)
+       .globl handle_exception
+handle_exception:
         SAVE_ALL
 handle_exception_saved:
         testb $X86_EFLAGS_IF>>8,UREGS_eflags+1(%rsp)
@@ -585,10 +587,6 @@
         movl  $TRAP_alignment_check,4(%rsp)
         jmp   handle_exception
 
-ENTRY(page_fault)
-        movl  $TRAP_page_fault,4(%rsp)
-        jmp   handle_exception
-
 ENTRY(spurious_interrupt_bug)
         pushq $0
         movl  $TRAP_spurious_int,4(%rsp)

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