x86: Disable paging before changing to long mode

This is required as part of the procedure. The existing code works
because it changes the GDT at the same time, but this makes kvm
unhappy.

Update the algorithm to disable and then re-enable paging.

Signed-off-by: Simon Glass <sjg@chromium.org>

arch/x86/cpu/i386/call64.S

@@ -25,6 +25,11 @@ cpu_call64:
 	push	%edx		/* arg1 = setup_base */
 	mov	%eax, %ebx
 
+	# disable paging
+	movl	%cr0, %eax
+	andl	$~X86_CR0_PG, %eax
+	movl	%eax, %cr0
+
 	/* Load new GDT with the 64bit segments using 32bit descriptor */
 	leal	gdt, %eax
 	movl	%eax, gdt+2
@@ -67,7 +72,8 @@ cpu_call64:
 	pushl	%eax
 
 	/* Enter paged protected Mode, activating Long Mode */
-	movl	$(X86_CR0_PG | X86_CR0_PE), %eax
+	movl	%cr0, %eax
+	orl	$X86_CR0_PG, %eax
 	movl	%eax, %cr0
 
 	/* Jump from 32bit compatibility mode into 64bit mode. */