x86/mm: Initialize vmemmap_base at boot-time

vmemmap area has different placement depending on paging mode.
Let's adjust it during early boot accodring to machine capability.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-mm@kvack.org
Link: http://lkml.kernel.org/r/20180214182542.69302-6-kirill.shutemov@linux.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/include/asm/pgtable_64_types.h

@@ -108,11 +108,8 @@ extern unsigned int ptrs_per_p4d;
 #define VMALLOC_SIZE_TB_L4	32UL
 #define VMALLOC_SIZE_TB_L5	12800UL
 
-#ifdef CONFIG_X86_5LEVEL
-# define __VMEMMAP_BASE		_AC(0xffd4000000000000, UL)
-#else
-# define __VMEMMAP_BASE		_AC(0xffffea0000000000, UL)
-#endif
+#define __VMEMMAP_BASE_L4	0xffffea0000000000
+#define __VMEMMAP_BASE_L5	0xffd4000000000000
 
 #ifdef CONFIG_DYNAMIC_MEMORY_LAYOUT
 # define VMALLOC_START		vmalloc_base
@@ -121,7 +118,7 @@ extern unsigned int ptrs_per_p4d;
 #else
 # define VMALLOC_START		__VMALLOC_BASE_L4
 # define VMALLOC_SIZE_TB	VMALLOC_SIZE_TB_L4
-# define VMEMMAP_START		__VMEMMAP_BASE
+# define VMEMMAP_START		__VMEMMAP_BASE_L4
 #endif /* CONFIG_DYNAMIC_MEMORY_LAYOUT */
 
 #define VMALLOC_END		(VMALLOC_START + (VMALLOC_SIZE_TB << 40) - 1)

arch/x86/kernel/head64.c

@@ -53,7 +53,7 @@ unsigned long page_offset_base __ro_after_init = __PAGE_OFFSET_BASE_L4;
 EXPORT_SYMBOL(page_offset_base);
 unsigned long vmalloc_base __ro_after_init = __VMALLOC_BASE_L4;
 EXPORT_SYMBOL(vmalloc_base);
-unsigned long vmemmap_base __ro_after_init = __VMEMMAP_BASE;
+unsigned long vmemmap_base __ro_after_init = __VMEMMAP_BASE_L4;
 EXPORT_SYMBOL(vmemmap_base);
 #endif
 
@@ -88,6 +88,7 @@ static void __head check_la57_support(unsigned long physaddr)
 	*fixup_int(&ptrs_per_p4d, physaddr) = 512;
 	*fixup_long(&page_offset_base, physaddr) = __PAGE_OFFSET_BASE_L5;
 	*fixup_long(&vmalloc_base, physaddr) = __VMALLOC_BASE_L5;
+	*fixup_long(&vmemmap_base, physaddr) = __VMEMMAP_BASE_L5;
 }
 #else
 static void __head check_la57_support(unsigned long physaddr) {}