powerpc/mm: Fix build error with FLATMEM book3s64 config

[linux-2.6-block.git] / arch / powerpc / include / asm / book3s / 64 / mmu.h

diff --git a/arch/powerpc/include/asm/book3s/64/mmu.h b/arch/powerpc/include/asm/book3s/64/mmu.h
index 1ceee000c18d7e6b9efc84a831c2c4ebc915405a..a809bdd77322783d4109be90ef0d888fdcf682df 100644 (file)
--- a/arch/powerpc/include/asm/book3s/64/mmu.h
+++ b/arch/powerpc/include/asm/book3s/64/mmu.h
@@ -35,6 +35,21 @@ typedef pte_t *pgtable_t;
 
 #endif /* __ASSEMBLY__ */
 
+/*
+ * If we store section details in page->flags we can't increase the MAX_PHYSMEM_BITS
+ * if we increase SECTIONS_WIDTH we will not store node details in page->flags and
+ * page_to_nid does a page->section->node lookup
+ * Hence only increase for VMEMMAP. Further depending on SPARSEMEM_EXTREME reduce
+ * memory requirements with large number of sections.
+ * 51 bits is the max physical real address on POWER9
+ */
+#if defined(CONFIG_SPARSEMEM_VMEMMAP) && defined(CONFIG_SPARSEMEM_EXTREME) &&  \
+       defined(CONFIG_PPC_64K_PAGES)
+#define MAX_PHYSMEM_BITS 51
+#else
+#define MAX_PHYSMEM_BITS 46
+#endif
+
 /* 64-bit classic hash table MMU */
 #include <asm/book3s/64/mmu-hash.h>