powerpc/mm/hash: Simplify the region id calculation.

This reduces multiple comparisons in get_region_id to a bit shift operation.
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/include/asm/book3s/64/hash-4k.h

@@ -13,12 +13,14 @@
  */
 #define MAX_EA_BITS_PER_CONTEXT		46
 
+#define REGION_SHIFT		(MAX_EA_BITS_PER_CONTEXT - 2)
+
 /*
  * Our page table limit us to 64TB. Hence for the kernel mapping,
  * each MAP area is limited to 16 TB.
  * The four map areas are:  linear mapping, vmap, IO and vmemmap
  */
-#define H_KERN_MAP_SIZE		(ASM_CONST(1) << (MAX_EA_BITS_PER_CONTEXT - 2))
+#define H_KERN_MAP_SIZE		(ASM_CONST(1) << REGION_SHIFT)
 
 /*
  * Define the address range of the kernel non-linear virtual area

arch/powerpc/include/asm/book3s/64/hash-64k.h

@@ -13,6 +13,7 @@
  * is handled in the hotpath.
  */
 #define MAX_EA_BITS_PER_CONTEXT		49
+#define REGION_SHIFT		MAX_EA_BITS_PER_CONTEXT
 
 /*
  * We use one context for each MAP area.

arch/powerpc/include/asm/book3s/64/hash.h

@@ -83,26 +83,26 @@
 #define H_VMEMMAP_SIZE		H_KERN_MAP_SIZE
 #define H_VMEMMAP_END		(H_VMEMMAP_START + H_VMEMMAP_SIZE)
 
+#define NON_LINEAR_REGION_ID(ea)	((((unsigned long)ea - H_KERN_VIRT_START) >> REGION_SHIFT) + 2)
+
 /*
  * Region IDs
  */
-#define USER_REGION_ID		1
-#define KERNEL_REGION_ID	2
-#define VMALLOC_REGION_ID	3
-#define IO_REGION_ID		4
-#define VMEMMAP_REGION_ID	5
+#define USER_REGION_ID		0
+#define KERNEL_REGION_ID	1
+#define VMALLOC_REGION_ID	NON_LINEAR_REGION_ID(H_VMALLOC_START)
+#define IO_REGION_ID		NON_LINEAR_REGION_ID(H_KERN_IO_START)
+#define VMEMMAP_REGION_ID	NON_LINEAR_REGION_ID(H_VMEMMAP_START)
 
 /*
  * Defines the address of the vmemap area, in its own region on
  * hash table CPUs.
  */
-
 #ifdef CONFIG_PPC_MM_SLICES
 #define HAVE_ARCH_UNMAPPED_AREA
 #define HAVE_ARCH_UNMAPPED_AREA_TOPDOWN
 #endif /* CONFIG_PPC_MM_SLICES */
 
-
 /* PTEIDX nibble */
 #define _PTEIDX_SECONDARY	0x8
 #define _PTEIDX_GROUP_IX	0x7
@@ -113,22 +113,21 @@
 #ifndef __ASSEMBLY__
 static inline int get_region_id(unsigned long ea)
 {
+	int region_id;
 	int id = (ea >> 60UL);
 
 	if (id == 0)
 		return USER_REGION_ID;
 
-	VM_BUG_ON(id != 0xc);
-	VM_BUG_ON(ea >= H_VMEMMAP_END);
+	if (ea < H_KERN_VIRT_START)
+		return KERNEL_REGION_ID;
 
-	if (ea >= H_VMEMMAP_START)
-		return VMEMMAP_REGION_ID;
-	else if (ea >= H_KERN_IO_START)
-		return IO_REGION_ID;
-	else if (ea >= H_VMALLOC_START)
-		return VMALLOC_REGION_ID;
+	VM_BUG_ON(id != 0xc);
+	BUILD_BUG_ON(NON_LINEAR_REGION_ID(H_VMALLOC_START) != 2);
 
-	return KERNEL_REGION_ID;
+	region_id = NON_LINEAR_REGION_ID(ea);
+	VM_BUG_ON(region_id > VMEMMAP_REGION_ID);
+	return region_id;
 }
 
 #define	hash__pmd_bad(pmd)		(pmd_val(pmd) & H_PMD_BAD_BITS)

arch/powerpc/include/asm/book3s/64/mmu-hash.h

@@ -823,7 +823,7 @@ static inline unsigned long get_kernel_context(unsigned long ea)
 		 */
 		ctx =  1 + ((ea & EA_MASK) >> MAX_EA_BITS_PER_CONTEXT);
 	} else
-		ctx = region_id + MAX_KERNEL_CTX_CNT - 2;
+		ctx = region_id + MAX_KERNEL_CTX_CNT - 1;
 	return ctx;
 }