[PATCH][2.6-mm] Fix 4G/4G X11/vm86 oops

[Zwane Mwaikambo]

The 4G/4G page fault handling path doesn't appear to handle faults 
happening whilst in vm86. The regs->xcs != __USER_CS so it confused the in 
kernel test.

However i'm still debugging the X11 triple fault in test9-mm3

Unable to handle kernel paging request at virtual address 00002000
 printing eip:
00007341
*pde = 00000000
Oops: 0004 [#1]
SMP DEBUG_PAGEALLOC
CPU:    0
EIP:    c000:[<00007341>]    Not tainted VLI
EFLAGS: 00033246
EIP is at 0x7341
eax: 32454256   ebx: 00000000   ecx: 00000000   edx: 00000000
esi: 00000000   edi: 00002000   ebp: 00000fd6   esp: 087bbf24
ds: 0000   es: 0000   ss: 0068
Process X (pid: 939, threadinfo=087ba000 task=0891c690)
Stack: 00000fcb 00000100 00000000 0000c000 00000000 00000000 00000000 00000000
       00000005 ffffffff ffffffff ffffffff ffffffff ffffffff ffffffff ffffffff
       ffffffff ffffffff ffffffff ffffffff ffffffff ffffffff ffffffff ffffffff
Call Trace:

Index: linux-2.6.0-test9-mm3/arch/i386/mm/fault.c
===================================================================
RCS file: /build/cvsroot/linux-2.6.0-test9-mm3/arch/i386/mm/fault.c,v
retrieving revision 1.1.1.1
diff -u -p -B -r1.1.1.1 fault.c
--- linux-2.6.0-test9-mm3/arch/i386/mm/fault.c	13 Nov 2003 08:07:17 -0000	1.1.1.1
+++ linux-2.6.0-test9-mm3/arch/i386/mm/fault.c	15 Nov 2003 19:08:34 -0000
@@ -264,7 +264,9 @@ asmlinkage void do_page_fault(struct pt_
 		if (error_code & 3)
 			goto bad_area_nosemaphore;
 
- 		goto vmalloc_fault;
+		/* If it's vm86 fall through */
+		if (!(error_code & 4))
+			goto vmalloc_fault;
 	}
 #else
 	if (unlikely(address >= TASK_SIZE)) { 
-
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