ARC: Make vmalloc size configurable

On ARC, lower 2G of address space is translated and used for
 - user vaddr space (region 0 to 5)
 - unused kernel-user gutter (region 6)
 - kernel vaddr space (region 7)

where each region simply represents 256MB of address space.

The kernel vaddr space of 256MB is used to implement vmalloc, modules
So far this was enough, but not on EZChip system with 4K CPUs (given
that per cpu mechanism uses vmalloc for allocating chunks)

So allow VMALLOC_SIZE to be configurable by expanding down into the unused
kernel-user gutter region which at default 256M was excessive anyways.

Also use _BITUL() to fix a build error since PGDIR_SIZE cannot use "1UL"
as called from assembly code in mm/tlbex.S

Signed-off-by: Noam Camus <noamc@ezchip.com>
[vgupta: rewrote changelog, debugged bootup crash due to int vs. hex]
Acked-by: Vineet Gupta <vgupta@synopsys.com>

arch/arc/Kconfig

@@ -492,6 +492,17 @@ config ARCH_DMA_ADDR_T_64BIT
 config ARC_PLAT_NEEDS_PHYS_TO_DMA
 	bool
 
+config ARC_KVADDR_SIZE
+	int "Kernel Virtaul Address Space size (MB)"
+	range 0 512
+	default "256"
+	help
+	  The kernel address space is carved out of 256MB of translated address
+	  space for catering to vmalloc, modules, pkmap, fixmap. This however may
+	  not suffice vmalloc requirements of a 4K CPU EZChip system. So allow
+	  this to be stretched to 512 MB (by extending into the reserved
+	  kernel-user gutter)
+
 config ARC_CURR_IN_REG
 	bool "Dedicate Register r25 for current_task pointer"
 	default y

arch/arc/include/asm/pgtable.h

@@ -217,7 +217,7 @@
 #define BITS_FOR_PTE	(PGDIR_SHIFT - PAGE_SHIFT)
 #define BITS_FOR_PGD	(32 - PGDIR_SHIFT)
 
-#define PGDIR_SIZE	(1UL << PGDIR_SHIFT)	/* vaddr span, not PDG sz */
+#define PGDIR_SIZE	_BITUL(PGDIR_SHIFT)	/* vaddr span, not PDG sz */
 #define PGDIR_MASK	(~(PGDIR_SIZE-1))
 
 #define	PTRS_PER_PTE	_BITUL(BITS_FOR_PTE)

arch/arc/include/asm/processor.h

@@ -97,7 +97,7 @@ extern unsigned int get_wchan(struct task_struct *p);
 #endif /* !__ASSEMBLY__ */
 
 /*
- * System Memory Map on ARC
+ * Default System Memory Map on ARC
  *
  * ---------------------------- (lower 2G, Translated) -------------------------
  * 0x0000_0000		0x5FFF_FFFF	(user vaddr: TASK_SIZE)
@@ -109,18 +109,17 @@ extern unsigned int get_wchan(struct task_struct *p);
  * 0xC000_0000		0xFFFF_FFFF	(peripheral uncached space)
  * -----------------------------------------------------------------------------
  */
-#define VMALLOC_START	0x70000000
 
-/*
- * 1 PGDIR_SIZE each for fixmap/pkmap, 2 PGDIR_SIZE gutter
- * See asm/highmem.h for details
- */
-#define VMALLOC_SIZE	(PAGE_OFFSET - VMALLOC_START - PGDIR_SIZE * 4)
-#define VMALLOC_END	(VMALLOC_START + VMALLOC_SIZE)
+#define TASK_SIZE	0x60000000
 
-#define USER_KERNEL_GUTTER    0x10000000
+#define VMALLOC_START	(PAGE_OFFSET - (CONFIG_ARC_KVADDR_SIZE << 20))
+
+/* 1 PGDIR_SIZE each for fixmap/pkmap, 2 PGDIR_SIZE gutter (see asm/highmem.h) */
+#define VMALLOC_SIZE	((CONFIG_ARC_KVADDR_SIZE << 20) - PGDIR_SIZE * 4)
+
+#define VMALLOC_END	(VMALLOC_START + VMALLOC_SIZE)
 
-#define TASK_SIZE	(VMALLOC_START - USER_KERNEL_GUTTER)
+#define USER_KERNEL_GUTTER    (VMALLOC_START - TASK_SIZE)
 
 #define STACK_TOP       TASK_SIZE
 #define STACK_TOP_MAX   STACK_TOP

arch/arc/mm/tlb.c

@@ -814,6 +814,11 @@ void arc_mmu_init(void)
 
 	printk(arc_mmu_mumbojumbo(0, str, sizeof(str)));
 
+	/*
+	 * Can't be done in processor.h due to header include depenedencies
+	 */
+	BUILD_BUG_ON(!IS_ALIGNED((CONFIG_ARC_KVADDR_SIZE << 20), PMD_SIZE));
+
 	/* For efficiency sake, kernel is compile time built for a MMU ver
 	 * This must match the hardware it is running on.
 	 * Linux built for MMU V2, if run on MMU V1 will break down because V1