arm64: Force SPARSEMEM_VMEMMAP as the only memory management model

Currently arm64 allows a choice of FLATMEM, SPARSEMEM and
SPARSEMEM_VMEMMAP. However, only the latter is tested regularly. FLATMEM
does not seem to boot in certain configurations (guest under KVM with
Qemu as a VMM). Since the reduction of the SECTION_SIZE_BITS to 27 (4K
pages) or 29 (64K page), there's little argument against the memory
wasted by the mem_map array with SPARSEMEM.

Make SPARSEMEM_VMEMMAP the only available option, non-selectable, and
remove the corresponding #ifdefs under arch/arm64/.
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Acked-by: Will Deacon <will@kernel.org>
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Acked-by: Marc Zyngier <maz@kernel.org>
Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
Acked-by: Mike Rapoport <rppt@linux.ibm.com>
Link: https://lore.kernel.org/r/20210420093559.23168-1-catalin.marinas@arm.comSigned-off-by: Catalin Marinas <catalin.marinas@arm.com>

arch/arm64/Kconfig

@@ -1040,15 +1040,7 @@ source "kernel/Kconfig.hz"
 config ARCH_SPARSEMEM_ENABLE
 	def_bool y
 	select SPARSEMEM_VMEMMAP_ENABLE
-
-config ARCH_SPARSEMEM_DEFAULT
-	def_bool ARCH_SPARSEMEM_ENABLE
-
-config ARCH_SELECT_MEMORY_MODEL
-	def_bool ARCH_SPARSEMEM_ENABLE
-
-config ARCH_FLATMEM_ENABLE
-	def_bool !NUMA
+	select SPARSEMEM_VMEMMAP
 
 config HW_PERF_EVENTS
 	def_bool y

arch/arm64/include/asm/kernel-pgtable.h

@@ -136,7 +136,7 @@
  * has a direct correspondence, and needs to appear sufficiently aligned
  * in the virtual address space.
  */
-#if defined(CONFIG_SPARSEMEM_VMEMMAP) && ARM64_MEMSTART_SHIFT < SECTION_SIZE_BITS
+#if ARM64_MEMSTART_SHIFT < SECTION_SIZE_BITS
 #define ARM64_MEMSTART_ALIGN	(1UL << SECTION_SIZE_BITS)
 #else
 #define ARM64_MEMSTART_ALIGN	(1UL << ARM64_MEMSTART_SHIFT)

arch/arm64/include/asm/memory.h

@@ -329,7 +329,7 @@ static inline void *phys_to_virt(phys_addr_t x)
  */
 #define ARCH_PFN_OFFSET		((unsigned long)PHYS_PFN_OFFSET)
 
-#if !defined(CONFIG_SPARSEMEM_VMEMMAP) || defined(CONFIG_DEBUG_VIRTUAL)
+#if defined(CONFIG_DEBUG_VIRTUAL)
 #define page_to_virt(x)	({						\
 	__typeof__(x) __page = x;					\
 	void *__addr = __va(page_to_phys(__page));			\
@@ -349,7 +349,7 @@ static inline void *phys_to_virt(phys_addr_t x)
 	u64 __addr = VMEMMAP_START + (__idx * sizeof(struct page));	\
 	(struct page *)__addr;						\
 })
-#endif /* !CONFIG_SPARSEMEM_VMEMMAP || CONFIG_DEBUG_VIRTUAL */
+#endif /* CONFIG_DEBUG_VIRTUAL */
 
 #define virt_addr_valid(addr)	({					\
 	__typeof__(addr) __addr = __tag_reset(addr);			\

arch/arm64/include/asm/sparsemem.h

@@ -5,7 +5,6 @@
 #ifndef __ASM_SPARSEMEM_H
 #define __ASM_SPARSEMEM_H
 
-#ifdef CONFIG_SPARSEMEM
 #define MAX_PHYSMEM_BITS	CONFIG_ARM64_PA_BITS
 
 /*
@@ -27,6 +26,4 @@
 #define SECTION_SIZE_BITS 27
 #endif /* CONFIG_ARM64_64K_PAGES */
 
-#endif /* CONFIG_SPARSEMEM*/
-
 #endif

arch/arm64/mm/init.c

@@ -220,6 +220,7 @@ static void __init zone_sizes_init(unsigned long min, unsigned long max)
 int pfn_valid(unsigned long pfn)
 {
 	phys_addr_t addr = PFN_PHYS(pfn);
+	struct mem_section *ms;
 
 	/*
 	 * Ensure the upper PAGE_SHIFT bits are clear in the
@@ -230,10 +231,6 @@ int pfn_valid(unsigned long pfn)
 	if (PHYS_PFN(addr) != pfn)
 		return 0;
 
-#ifdef CONFIG_SPARSEMEM
-{
-	struct mem_section *ms;
-
 	if (pfn_to_section_nr(pfn) >= NR_MEM_SECTIONS)
 		return 0;
 
@@ -252,8 +249,7 @@ int pfn_valid(unsigned long pfn)
 	 */
 	if (!early_section(ms))
 		return pfn_section_valid(ms, pfn);
-}
-#endif
+
 	return memblock_is_map_memory(addr);
 }
 EXPORT_SYMBOL(pfn_valid);

arch/arm64/mm/mmu.c

@@ -1113,7 +1113,6 @@ static void free_empty_tables(unsigned long addr, unsigned long end,
 }
 #endif
 
-#ifdef CONFIG_SPARSEMEM_VMEMMAP
 #if !ARM64_SWAPPER_USES_SECTION_MAPS
 int __meminit vmemmap_populate(unsigned long start, unsigned long end, int node,
 		struct vmem_altmap *altmap)
@@ -1177,7 +1176,6 @@ void vmemmap_free(unsigned long start, unsigned long end,
 	free_empty_tables(start, end, VMEMMAP_START, VMEMMAP_END);
 #endif
 }
-#endif	/* CONFIG_SPARSEMEM_VMEMMAP */
 
 static inline pud_t *fixmap_pud(unsigned long addr)
 {

arch/arm64/mm/ptdump.c

@@ -51,10 +51,8 @@ static struct addr_marker address_markers[] = {
 	{ FIXADDR_TOP,			"Fixmap end" },
 	{ PCI_IO_START,			"PCI I/O start" },
 	{ PCI_IO_END,			"PCI I/O end" },
-#ifdef CONFIG_SPARSEMEM_VMEMMAP
 	{ VMEMMAP_START,		"vmemmap start" },
 	{ VMEMMAP_START + VMEMMAP_SIZE,	"vmemmap end" },
-#endif
 	{ -1,				NULL },
 };