arm64: mm: Move PCI I/O emulation region above the vmemmap region

Move the PCI I/O region above the vmemmap region in the kernel's VA
space. This will permit us to reclaim the lower part of the vmemmap
region for vmalloc/vmap allocations when running a 52-bit VA capable
build on a 48-bit VA capable system.

Also, given that PCI_IO_START is derived from VMEMMAP_END, use that
symbolic constant directly in ptdump rather than deriving it from
VMEMMAP_START and VMEMMAP_SIZE, as those definitions will change in
subsequent patches.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20231213084024.2367360-10-ardb@google.comSigned-off-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Mark Rutland <mark.rutland@arm.com>

arch/arm64/include/asm/memory.h

@@ -49,8 +49,8 @@
 #define MODULES_VSIZE		(SZ_2G)
 #define VMEMMAP_START		(-(UL(1) << (VA_BITS - VMEMMAP_SHIFT)))
 #define VMEMMAP_END		(VMEMMAP_START + VMEMMAP_SIZE)
-#define PCI_IO_END		(VMEMMAP_START - SZ_8M)
-#define PCI_IO_START		(PCI_IO_END - PCI_IO_SIZE)
+#define PCI_IO_START		(VMEMMAP_END + SZ_8M)
+#define PCI_IO_END		(PCI_IO_START + PCI_IO_SIZE)
 #define FIXADDR_TOP		(VMEMMAP_START - SZ_32M)
 
 #if VA_BITS > 48

arch/arm64/mm/ptdump.c

@@ -47,10 +47,10 @@ static struct addr_marker address_markers[] = {
 	{ VMALLOC_END,			"vmalloc() end" },
 	{ FIXADDR_TOT_START,		"Fixmap start" },
 	{ FIXADDR_TOP,			"Fixmap end" },
+	{ VMEMMAP_START,		"vmemmap start" },
+	{ VMEMMAP_END,			"vmemmap end" },
 	{ PCI_IO_START,			"PCI I/O start" },
 	{ PCI_IO_END,			"PCI I/O end" },
-	{ VMEMMAP_START,		"vmemmap start" },
-	{ VMEMMAP_START + VMEMMAP_SIZE,	"vmemmap end" },
 	{ -1,				NULL },
 };