x86 ACPI: normalize segment descriptor register on resume

Some Dell laptops enter resume with apparent garbage in the segment
descriptor registers (almost certainly the result of a botched
transition from protected to real mode.)  The only way to clean that
up is to enter protected mode ourselves and clean out the descriptor
registers.

This fixes resume on Dell XPS M1210 and Dell D620.

Reference: http://bugzilla.kernel.org/show_bug.cgi?id=10927

Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: pm list <linux-pm@lists.linux-foundation.org>
Cc: Len Brown <lenb@kernel.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Tested-by: Kirill A. Shutemov <kirill@shutemov.name>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 37 insertions, 1 deletions

diff --git a/arch/x86/kernel/acpi/realmode/wakeup.S b/arch/x86/kernel/acpi/realmode/wakeup.S
index f9b77fb37e5b..3355973b12ac 100644
--- a/arch/x86/kernel/acpi/realmode/wakeup.S
+++ b/arch/x86/kernel/acpi/realmode/wakeup.S
@@ -5,6 +5,7 @@
 #include <asm/msr-index.h>
 #include <asm/page.h>
 #include <asm/pgtable.h>
+#include <asm/processor-flags.h>
 
         .code16
         .section ".header", "a"
@@ -24,6 +25,11 @@ pmode_gdt:	.quad	0
 realmode_flags: .long   0
 real_magic:     .long   0
 trampoline_segment:     .word 0
+_pad1:          .byte   0
+wakeup_jmp:     .byte   0xea    /* ljmpw */
+wakeup_jmp_off: .word   3f
+wakeup_jmp_seg: .word   0
+wakeup_gdt:     .quad   0, 0, 0
 signature:      .long   0x51ee1111
 
         .text
@@ -34,11 +40,34 @@ _start:
         cli
         cld
 
+        /* Apparently some dimwit BIOS programmers don't know how to
+           program a PM to RM transition, and we might end up here with
+           junk in the data segment descriptor registers.  The only way
+           to repair that is to go into PM and fix it ourselves... */
+        movw    $16, %cx
+        lgdtl   %cs:wakeup_gdt
+        movl    %cr0, %eax
+        orb     $X86_CR0_PE, %al
+        movl    %eax, %cr0
+        jmp     1f
+1:      ljmpw   $8, $2f
+2:
+        movw    %cx, %ds
+        movw    %cx, %es
+        movw    %cx, %ss
+        movw    %cx, %fs
+        movw    %cx, %gs
+
+        andb    $~X86_CR0_PE, %al
+        movl    %eax, %cr0
+        jmp     wakeup_jmp
+3:
         /* Set up segments */
         movw    %cs, %ax
         movw    %ax, %ds
         movw    %ax, %es
         movw    %ax, %ss
+        lidtl   wakeup_idt
 
         movl    $wakeup_stack_end, %esp
 
@@ -98,7 +127,14 @@ bogus_real_magic:
         jmp     1b
 
         .data
-        .balign 4
+        .balign 8
+
+        /* This is the standard real-mode IDT */
+wakeup_idt:
+        .word   0xffff          /* limit */
+        .long   0               /* address */
+        .word   0
+
         .globl  HEAP, heap_end
 HEAP:
         .long   wakeup_heap