[IA64] Sparse virtual implementation

Equip IA64 sparsemem with a virtual memmap. This is similar to the existing
CONFIG_VMEMMAP functionality for discontig. It uses a page size mapping.

This is provided as a minimally intrusive solution. We split the
128TB VMALLOC area into two 64TB areas and use one for the virtual memmap.

I have another patch in testing that uses granule sized 16MB pages to map
the memmap but this would require changes to the interrupt vector table
and there are certain discussions that would need to take place
before we can accept such a large page size for the memmap. However, it
would significantly reduce TLB pressure and not take a portion of VMALLOC
space.

Signed-off-by: Christoph Lameter <clameter@sgi.com>

Index: linux-2.6.21-rc5-mm2/arch/ia64/Kconfig
===================================================================
--- linux-2.6.21-rc5-mm2.orig/arch/ia64/Kconfig	2007-04-02 16:15:29.000000000 -0700
+++ linux-2.6.21-rc5-mm2/arch/ia64/Kconfig	2007-04-02 16:15:50.000000000 -0700
@@ -350,6 +350,10 @@ config ARCH_SPARSEMEM_ENABLE
 	def_bool y
 	depends on ARCH_DISCONTIGMEM_ENABLE
 
+config SPARSE_VIRTUAL
+	def_bool y
+	depends on ARCH_SPARSEMEM_ENABLE
+
 config ARCH_DISCONTIGMEM_DEFAULT
 	def_bool y if (IA64_SGI_SN2 || IA64_GENERIC || IA64_HP_ZX1 || IA64_HP_ZX1_SWIOTLB)
 	depends on ARCH_DISCONTIGMEM_ENABLE
Index: linux-2.6.21-rc5-mm2/include/asm-ia64/page.h
===================================================================
--- linux-2.6.21-rc5-mm2.orig/include/asm-ia64/page.h	2007-04-02 16:15:29.000000000 -0700
+++ linux-2.6.21-rc5-mm2/include/asm-ia64/page.h	2007-04-02 16:15:50.000000000 -0700
@@ -106,6 +106,9 @@ extern int ia64_pfn_valid (unsigned long
 # define ia64_pfn_valid(pfn) 1
 #endif
 
+#define vmemmap ((struct page *)(RGN_BASE(RGN_GATE) + \
+				(1UL << (4*PAGE_SHIFT - 10))))
+
 #ifdef CONFIG_VIRTUAL_MEM_MAP
 extern struct page *vmem_map;
 #ifdef CONFIG_DISCONTIGMEM
Index: linux-2.6.21-rc5-mm2/include/asm-ia64/pgtable.h
===================================================================
--- linux-2.6.21-rc5-mm2.orig/include/asm-ia64/pgtable.h	2007-04-02 16:15:29.000000000 -0700
+++ linux-2.6.21-rc5-mm2/include/asm-ia64/pgtable.h	2007-04-02 16:15:50.000000000 -0700
@@ -236,8 +236,13 @@ ia64_phys_addr_valid (unsigned long addr
 # define VMALLOC_END		vmalloc_end
   extern unsigned long vmalloc_end;
 #else
+#if defined(CONFIG_SPARSEMEM) && defined(CONFIG_SPARSE_VIRTUAL)
+/* SPARSE_VIRTUAL uses half of vmalloc... */
+# define VMALLOC_END		(RGN_BASE(RGN_GATE) + (1UL << (4*PAGE_SHIFT - 10)))
+#else
 # define VMALLOC_END		(RGN_BASE(RGN_GATE) + (1UL << (4*PAGE_SHIFT - 9)))
 #endif
+#endif
 
 /* fs/proc/kcore.c */
 #define	kc_vaddr_to_offset(v) ((v) - RGN_BASE(RGN_GATE))