xen/mmu/p2m: Refactor the xen_pagetable_init code (v2).

The revectoring and copying of the P2M only happens when
!auto-xlat and on 64-bit builds. It is not obvious from
the code, so lets have seperate 32 and 64-bit functions.

We also invert the check for auto-xlat to make the code
flow simpler.
Suggested-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

arch/x86/xen/mmu.c

@@ -1198,19 +1198,15 @@ static void __init xen_cleanhighmap(unsigned long vaddr,
 	 * instead of somewhere later and be confusing. */
 	xen_mc_flush();
 }
-#endif
-static void __init xen_pagetable_init(void)
+static void __init xen_pagetable_p2m_copy(void)
 {
-#ifdef CONFIG_X86_64
 	unsigned long size;
 	unsigned long addr;
-#endif
-	paging_init();
-	xen_setup_shared_info();
-#ifdef CONFIG_X86_64
-	if (!xen_feature(XENFEAT_auto_translated_physmap)) {
 	unsigned long new_mfn_list;
 
+	if (xen_feature(XENFEAT_auto_translated_physmap))
+		return;
+
 	size = PAGE_ALIGN(xen_start_info->nr_pages * sizeof(unsigned long));
 
 	/* On 32-bit, we get zero so this never gets executed. */
@@ -1234,8 +1230,8 @@ static void __init xen_pagetable_init(void)
 		/* And revector! Bye bye old array */
 		xen_start_info->mfn_list = new_mfn_list;
 	} else
-			goto skip;
-	}
+		return;
+
 	/* At this stage, cleanup_highmap has already cleaned __ka space
 	 * from _brk_limit way up to the max_pfn_mapped (which is the end of
 	 * the ramdisk). We continue on, erasing PMD entries that point to page
@@ -1255,7 +1251,15 @@ static void __init xen_pagetable_init(void)
 	 * anything at this stage. */
 	xen_cleanhighmap(MODULES_VADDR, roundup(MODULES_VADDR, PUD_SIZE) - 1);
 #endif
-skip:
+}
+#endif
+
+static void __init xen_pagetable_init(void)
+{
+	paging_init();
+	xen_setup_shared_info();
+#ifdef CONFIG_X86_64
+	xen_pagetable_p2m_copy();
 #endif
 	xen_post_allocator_init();
 }