@@ -40,6 +40,7 @@ config ALPHA
 	select CPU_NO_EFFICIENT_FFS if !ALPHA_EV67
 	select MMU_GATHER_NO_RANGE
 	select SET_FS
+	select SPARSEMEM_EXTREME if SPARSEMEM
 	help
 	  The Alpha is a 64-bit general-purpose processor designed and
 	  marketed by the Digital Equipment Corporation of blessed memory,

@@ -551,12 +552,19 @@ config NR_CPUS
 
 config ARCH_DISCONTIGMEM_ENABLE
 	bool "Discontiguous Memory Support"
+	depends on BROKEN
 	help
 	  Say Y to support efficient handling of discontiguous physical memory,
 	  for architectures which are either NUMA (Non-Uniform Memory Access)
 	  or have huge holes in the physical address space for other reasons.
 	  See <file:Documentation/vm/numa.rst> for more.
 
+config ARCH_SPARSEMEM_ENABLE
+	bool "Sparse Memory Support"
+	help
+	  Say Y to support efficient handling of discontiguous physical memory,
+	  for systems that have huge holes in the physical address space.
+
 config NUMA
 	bool "NUMA Support (EXPERIMENTAL)"
 	depends on DISCONTIGMEM && BROKEN

@@ -6,6 +6,8 @@
 #ifndef _ASM_MMZONE_H_
 #define _ASM_MMZONE_H_
 
+#ifdef CONFIG_DISCONTIGMEM
+
 #include <asm/smp.h>
 
 /*

@@ -45,8 +47,6 @@ PLAT_NODE_DATA_LOCALNR(unsigned long p, int n)
 }
 #endif
 
-#ifdef CONFIG_DISCONTIGMEM
-
 /*
  * Following are macros that each numa implementation must define.
  */

@@ -68,11 +68,6 @@ PLAT_NODE_DATA_LOCALNR(unsigned long p, int n)
 /* XXX: FIXME -- nyc */
 #define kern_addr_valid(kaddr)	(0)
 
-#define virt_to_page(kaddr)	pfn_to_page(__pa(kaddr) >> PAGE_SHIFT)
-
-#define pmd_page(pmd)		(pfn_to_page(pmd_val(pmd) >> 32))
-#define pte_pfn(pte)		(pte_val(pte) >> 32)
-
 #define mk_pte(page, pgprot)						     \
 ({								 	     \
 	pte_t pte;                                                           \

@@ -95,16 +90,11 @@ PLAT_NODE_DATA_LOCALNR(unsigned long p, int n)
 	__xx;                                                           \
 })
 
-#define page_to_pa(page)						\
-	(page_to_pfn(page) << PAGE_SHIFT)
-
 #define pfn_to_nid(pfn)		pa_to_nid(((u64)(pfn) << PAGE_SHIFT))
 #define pfn_valid(pfn)							\
 	(((pfn) - node_start_pfn(pfn_to_nid(pfn))) <			\
 	 node_spanned_pages(pfn_to_nid(pfn)))					\
 
-#define virt_addr_valid(kaddr)	pfn_valid((__pa(kaddr) >> PAGE_SHIFT))
-
 #endif /* CONFIG_DISCONTIGMEM */
 
 #endif /* _ASM_MMZONE_H_ */

@@ -83,12 +83,13 @@ typedef struct page *pgtable_t;
 
 #define __pa(x)			((unsigned long) (x) - PAGE_OFFSET)
 #define __va(x)			((void *)((unsigned long) (x) + PAGE_OFFSET))
-#ifndef CONFIG_DISCONTIGMEM
+
 #define virt_to_page(kaddr)	pfn_to_page(__pa(kaddr) >> PAGE_SHIFT)
+#define virt_addr_valid(kaddr)	pfn_valid((__pa(kaddr) >> PAGE_SHIFT))
 
+#ifdef CONFIG_FLATMEM
 #define pfn_valid(pfn)		((pfn) < max_mapnr)
-#define virt_addr_valid(kaddr)	pfn_valid(__pa(kaddr) >> PAGE_SHIFT)
-#endif /* CONFIG_DISCONTIGMEM */
+#endif /* CONFIG_FLATMEM */
 
 #include <asm-generic/memory_model.h>
 #include <asm-generic/getorder.h>

@@ -203,10 +203,10 @@ extern unsigned long __zero_page(void);
  * Conversion functions:  convert a page and protection to a page entry,
  * and a page entry and page directory to the page they refer to.
  */
-#ifndef CONFIG_DISCONTIGMEM
-#define page_to_pa(page)	(((page) - mem_map) << PAGE_SHIFT)
-
+#define page_to_pa(page)	(page_to_pfn(page) << PAGE_SHIFT)
 #define pte_pfn(pte)	(pte_val(pte) >> 32)
+
+#ifndef CONFIG_DISCONTIGMEM
 #define pte_page(pte)	pfn_to_page(pte_pfn(pte))
 #define mk_pte(page, pgprot)						\
 ({									\

@@ -236,10 +236,8 @@ pmd_page_vaddr(pmd_t pmd)
 	return ((pmd_val(pmd) & _PFN_MASK) >> (32-PAGE_SHIFT)) + PAGE_OFFSET;
 }
 
-#ifndef CONFIG_DISCONTIGMEM
-#define pmd_page(pmd)	(mem_map + ((pmd_val(pmd) & _PFN_MASK) >> 32))
-#define pud_page(pud)	(mem_map + ((pud_val(pud) & _PFN_MASK) >> 32))
-#endif
+#define pmd_page(pmd)	(pfn_to_page(pmd_val(pmd) >> 32))
+#define pud_page(pud)	(pfn_to_page(pud_val(pud) >> 32))
 
 extern inline unsigned long pud_page_vaddr(pud_t pgd)
 { return PAGE_OFFSET + ((pud_val(pgd) & _PFN_MASK) >> (32-PAGE_SHIFT)); }

@@ -0,0 +1,18 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_ALPHA_SPARSEMEM_H
+#define _ASM_ALPHA_SPARSEMEM_H
+
+#ifdef CONFIG_SPARSEMEM
+
+#define SECTION_SIZE_BITS	27
+
+/*
+ * According to "Alpha Architecture Reference Manual" physical
+ * addresses are at most 48 bits.
+ * https://download.majix.org/dec/alpha_arch_ref.pdf
+ */
+#define MAX_PHYSMEM_BITS	48
+
+#endif /* CONFIG_SPARSEMEM */
+
+#endif /* _ASM_ALPHA_SPARSEMEM_H */

@@ -648,6 +648,7 @@ setup_arch(char **cmdline_p)
 	/* Find our memory.  */
 	setup_memory(kernel_end);
 	memblock_set_bottom_up(true);
+	sparse_init();
 
 	/* First guess at cpu cache sizes.  Do this before init_arch.  */
 	determine_cpu_caches(cpu->type);