arm64: mm: move vmemmap region right below the linear region
This moves the vmemmap region right below PAGE_OFFSET, aka the start
of the linear region, and redefines its size to be a power of two.
Due to the placement of PAGE_OFFSET in the middle of the address space,
whose size is a power of two as well, this guarantees that virt to
page conversions and vice versa can be implemented efficiently, by
masking and shifting rather than ordinary arithmetic.
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
diff --git a/arch/arm64/mm/dump.c b/arch/arm64/mm/dump.c
index f9271cb..a21f4742 100644
--- a/arch/arm64/mm/dump.c
+++ b/arch/arm64/mm/dump.c
@@ -37,14 +37,14 @@
MODULES_END_NR,
VMALLOC_START_NR,
VMALLOC_END_NR,
-#ifdef CONFIG_SPARSEMEM_VMEMMAP
- VMEMMAP_START_NR,
- VMEMMAP_END_NR,
-#endif
FIXADDR_START_NR,
FIXADDR_END_NR,
PCI_START_NR,
PCI_END_NR,
+#ifdef CONFIG_SPARSEMEM_VMEMMAP
+ VMEMMAP_START_NR,
+ VMEMMAP_END_NR,
+#endif
KERNEL_SPACE_NR,
};
@@ -53,14 +53,14 @@
{ MODULES_END, "Modules end" },
{ VMALLOC_START, "vmalloc() Area" },
{ VMALLOC_END, "vmalloc() End" },
-#ifdef CONFIG_SPARSEMEM_VMEMMAP
- { 0, "vmemmap start" },
- { 0, "vmemmap end" },
-#endif
{ FIXADDR_START, "Fixmap start" },
{ FIXADDR_TOP, "Fixmap end" },
{ PCI_IO_START, "PCI I/O start" },
{ PCI_IO_END, "PCI I/O end" },
+#ifdef CONFIG_SPARSEMEM_VMEMMAP
+ { 0, "vmemmap start" },
+ { 0, "vmemmap end" },
+#endif
{ PAGE_OFFSET, "Linear Mapping" },
{ -1, NULL },
};