[S390] add support for physical memory > 4TB

The kernel address space of a 64 bit kernel currently uses a three level
page table and the vmemmap array has a fixed address and a fixed maximum
size. A three level page table is good enough for systems with less than
3.8TB of memory, for bigger systems four page table levels need to be
used. Each page table level costs a bit of performance, use 3 levels for
normal systems and 4 levels only for the really big systems.
To avoid bloating sparse.o too much set MAX_PHYSMEM_BITS to 46 for a
maximum of 64TB of memory.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

1 files changed, 53 insertions, 14 deletions

diff --git a/arch/s390/kernel/setup.c b/arch/s390/kernel/setup.c
index 26b601c2b137..66903eed36e6 100644
--- a/arch/s390/kernel/setup.c
+++ b/arch/s390/kernel/setup.c
@@ -94,6 +94,15 @@ struct mem_chunk __initdata memory_chunk[MEMORY_CHUNKS];
 int __initdata memory_end_set;
 unsigned long __initdata memory_end;
 
+unsigned long VMALLOC_START;
+EXPORT_SYMBOL(VMALLOC_START);
+
+unsigned long VMALLOC_END;
+EXPORT_SYMBOL(VMALLOC_END);
+
+struct page *vmemmap;
+EXPORT_SYMBOL(vmemmap);
+
 /* An array with a pointer to the lowcore of every CPU. */
 struct _lowcore *lowcore_ptr[NR_CPUS];
 EXPORT_SYMBOL(lowcore_ptr);
@@ -277,6 +286,15 @@ static int __init early_parse_mem(char *p)
 }
 early_param("mem", early_parse_mem);
 
+static int __init parse_vmalloc(char *arg)
+{
+	if (!arg)
+		return -EINVAL;
+	VMALLOC_END = (memparse(arg, &arg) + PAGE_SIZE - 1) & PAGE_MASK;
+	return 0;
+}
+early_param("vmalloc", parse_vmalloc);
+
 unsigned int user_mode = HOME_SPACE_MODE;
 EXPORT_SYMBOL_GPL(user_mode);
 
@@ -478,8 +496,7 @@ EXPORT_SYMBOL_GPL(real_memory_size);
 
 static void __init setup_memory_end(void)
 {
-	unsigned long memory_size;
-	unsigned long max_mem;
+	unsigned long vmax, vmalloc_size, tmp;
 	int i;
 
 
@@ -489,12 +506,9 @@ static void __init setup_memory_end(void)
 		memory_end_set = 1;
 	}
 #endif
-	memory_size = 0;
+	real_memory_size = 0;
 	memory_end &= PAGE_MASK;
 
-	max_mem = memory_end ? min(VMEM_MAX_PHYS, memory_end) : VMEM_MAX_PHYS;
-	memory_end = min(max_mem, memory_end);
-
 	/*
 	 * Make sure all chunks are MAX_ORDER aligned so we don't need the
 	 * extra checks that HOLES_IN_ZONE would require.
@@ -514,23 +528,48 @@ static void __init setup_memory_end(void)
 			chunk->addr = start;
 			chunk->size = end - start;
 		}
+		real_memory_size = max(real_memory_size,
+				       chunk->addr + chunk->size);
 	}
 
+	/* Choose kernel address space layout: 2, 3, or 4 levels. */
+#ifdef CONFIG_64BIT
+	vmalloc_size = VMALLOC_END ?: 128UL << 30;
+	tmp = (memory_end ?: real_memory_size) / PAGE_SIZE;
+	tmp = tmp * (sizeof(struct page) + PAGE_SIZE) + vmalloc_size;
+	if (tmp <= (1UL << 42))
+		vmax = 1UL << 42;	/* 3-level kernel page table */
+	else
+		vmax = 1UL << 53;	/* 4-level kernel page table */
+#else
+	vmalloc_size = VMALLOC_END ?: 96UL << 20;
+	vmax = 1UL << 31;		/* 2-level kernel page table */
+#endif
+	/* vmalloc area is at the end of the kernel address space. */
+	VMALLOC_END = vmax;
+	VMALLOC_START = vmax - vmalloc_size;
+
+	/* Split remaining virtual space between 1:1 mapping & vmemmap array */
+	tmp = VMALLOC_START / (PAGE_SIZE + sizeof(struct page));
+	tmp = VMALLOC_START - tmp * sizeof(struct page);
+	tmp &= ~((vmax >> 11) - 1);	/* align to page table level */
+	tmp = min(tmp, 1UL << MAX_PHYSMEM_BITS);
+	vmemmap = (struct page *) tmp;
+
+	/* Take care that memory_end is set and <= vmemmap */
+	memory_end = min(memory_end ?: real_memory_size, tmp);
+
+	/* Fixup memory chunk array to fit into 0..memory_end */
 	for (i = 0; i < MEMORY_CHUNKS; i++) {
 		struct mem_chunk *chunk = &memory_chunk[i];
 
-		real_memory_size = max(real_memory_size,
-				       chunk->addr + chunk->size);
-		if (chunk->addr >= max_mem) {
+		if (chunk->addr >= memory_end) {
 			memset(chunk, 0, sizeof(*chunk));
 			continue;
 		}
-		if (chunk->addr + chunk->size > max_mem)
-			chunk->size = max_mem - chunk->addr;
-		memory_size = max(memory_size, chunk->addr + chunk->size);
+		if (chunk->addr + chunk->size > memory_end)
+			chunk->size = memory_end - chunk->addr;
 	}
-	if (!memory_end)
-		memory_end = memory_size;
 }
 
 void *restart_stack __attribute__((__section__(".data")));