x86: fix i486 suspend to disk CR4 oops

arch/x86/power/cpu_32.c __save_processor_state calls read_cr4()
only a i486 CPU doesn't have the CR4 register.  Trying to read it
produces an invalid opcode oops during suspend to disk.

Use the safe rc4 reading op instead. If the value to be written is
zero the write is skipped.

arch/x86/power/hibernate_asm_32.S
done: swapped the use of %eax and %ecx to use jecxz for
the zero test and jump over store to %cr4.
restore_image: s/%ecx/%eax/ to be consistent with done:

In addition to __save_processor_state, acpi_save_state_mem,
efi_call_phys_prelog, and efi_call_phys_epilog had checks added
(acpi restore was in assembly and already had a check for
non-zero).  There were other reads and writes of CR4, but MCE and
virtualization shouldn't be executed on a i486 anyway.
Signed-off-by: David Fries <david@fries.net>
Acked-by: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

arch/x86/kernel/acpi/sleep.c

@@ -86,7 +86,7 @@ int acpi_save_state_mem(void)
 #endif /* !CONFIG_64BIT */
 
 	header->pmode_cr0 = read_cr0();
-	header->pmode_cr4 = read_cr4();
+	header->pmode_cr4 = read_cr4_safe();
 	header->realmode_flags = acpi_realmode_flags;
 	header->real_magic = 0x12345678;
 

arch/x86/kernel/efi_32.c

@@ -53,7 +53,7 @@ void efi_call_phys_prelog(void)
 	 * directory. If I have PAE, I just need to duplicate one entry in
 	 * page directory.
 	 */
-	cr4 = read_cr4();
+	cr4 = read_cr4_safe();
 
 	if (cr4 & X86_CR4_PAE) {
 		efi_bak_pg_dir_pointer[0].pgd =
@@ -91,7 +91,7 @@ void efi_call_phys_epilog(void)
 	gdt_descr.size = GDT_SIZE - 1;
 	load_gdt(&gdt_descr);
 
-	cr4 = read_cr4();
+	cr4 = read_cr4_safe();
 
 	if (cr4 & X86_CR4_PAE) {
 		swapper_pg_dir[pgd_index(0)].pgd =

arch/x86/power/cpu_32.c

@@ -45,7 +45,7 @@ static void __save_processor_state(struct saved_context *ctxt)
 	ctxt->cr0 = read_cr0();
 	ctxt->cr2 = read_cr2();
 	ctxt->cr3 = read_cr3();
-	ctxt->cr4 = read_cr4();
+	ctxt->cr4 = read_cr4_safe();
 }
 
 /* Needed by apm.c */
@@ -98,7 +98,9 @@ static void __restore_processor_state(struct saved_context *ctxt)
 	/*
 	 * control registers
 	 */
-	write_cr4(ctxt->cr4);
+	/* cr4 was introduced in the Pentium CPU */
+	if (ctxt->cr4)
+		write_cr4(ctxt->cr4);
 	write_cr3(ctxt->cr3);
 	write_cr2(ctxt->cr2);
 	write_cr0(ctxt->cr0);

arch/x86/power/hibernate_asm_32.S

@@ -28,9 +28,9 @@ ENTRY(swsusp_arch_suspend)
 	ret
 
 ENTRY(restore_image)
-	movl	resume_pg_dir, %ecx
-	subl	$__PAGE_OFFSET, %ecx
-	movl	%ecx, %cr3
+	movl	resume_pg_dir, %eax
+	subl	$__PAGE_OFFSET, %eax
+	movl	%eax, %cr3
 
 	movl	restore_pblist, %edx
 	.p2align 4,,7
@@ -52,17 +52,21 @@ copy_loop:
 
 done:
 	/* go back to the original page tables */
-	movl	$swapper_pg_dir, %ecx
-	subl	$__PAGE_OFFSET, %ecx
-	movl	%ecx, %cr3
+	movl	$swapper_pg_dir, %eax
+	subl	$__PAGE_OFFSET, %eax
+	movl	%eax, %cr3
 	/* Flush TLB, including "global" things (vmalloc) */
-	movl	mmu_cr4_features, %eax
-	movl	%eax, %edx
+	movl	mmu_cr4_features, %ecx
+	jecxz	1f	# cr4 Pentium and higher, skip if zero
+	movl	%ecx, %edx
 	andl	$~(1<<7), %edx;  # PGE
 	movl	%edx, %cr4;  # turn off PGE
-	movl	%cr3, %ecx;  # flush TLB
-	movl	%ecx, %cr3
-	movl	%eax, %cr4;  # turn PGE back on
+1:
+	movl	%cr3, %eax;  # flush TLB
+	movl	%eax, %cr3
+	jecxz	1f	# cr4 Pentium and higher, skip if zero
+	movl	%ecx, %cr4;  # turn PGE back on
+1:
 
 	movl saved_context_esp, %esp
 	movl saved_context_ebp, %ebp