[PATCH V2 3/3] s390/mm: Define arch_get_mappable_range()

[Anshuman Khandual <anshuman.khandual@arm.com>]

This overrides arch_get_mappabble_range() on s390 platform which will be
used with recently added generic framework. It modifies the existing range
check in vmem_add_mapping() using arch_get_mappable_range(). It also adds a
VM_BUG_ON() check that would ensure that memhp_range_allowed() has already
been called on the hotplug path.

Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: linux-s390@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Acked-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
---
 arch/s390/mm/init.c |  1 +
 arch/s390/mm/vmem.c | 15 ++++++++++++++-
 2 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/arch/s390/mm/init.c b/arch/s390/mm/init.c
index 77767850d0d0..e0e78234ae57 100644
--- a/arch/s390/mm/init.c
+++ b/arch/s390/mm/init.c
@@ -291,6 +291,7 @@ int arch_add_memory(int nid, u64 start, u64 size,
 	if (WARN_ON_ONCE(params->pgprot.pgprot != PAGE_KERNEL.pgprot))
 		return -EINVAL;
 
+	VM_BUG_ON(!memhp_range_allowed(start, size, 1));
 	rc = vmem_add_mapping(start, size);
 	if (rc)
 		return rc;
diff --git a/arch/s390/mm/vmem.c b/arch/s390/mm/vmem.c
index b239f2ba93b0..e10e563ad2b4 100644
--- a/arch/s390/mm/vmem.c
+++ b/arch/s390/mm/vmem.c
@@ -4,6 +4,7 @@
  *    Author(s): Heiko Carstens <heiko.carstens@de.ibm.com>
  */
 
+#include <linux/memory_hotplug.h>
 #include <linux/memblock.h>
 #include <linux/pfn.h>
 #include <linux/mm.h>
@@ -532,11 +533,23 @@ void vmem_remove_mapping(unsigned long start, unsigned long size)
 	mutex_unlock(&vmem_mutex);
 }
 
+struct range arch_get_mappable_range(void)
+{
+	struct range memhp_range;
+
+	memhp_range.start = 0;
+	memhp_range.end =  VMEM_MAX_PHYS;
+	return memhp_range;
+}
+
 int vmem_add_mapping(unsigned long start, unsigned long size)
 {
+	struct range range;
 	int ret;
 
-	if (start + size > VMEM_MAX_PHYS ||
+	range = arch_get_mappable_range();
+	if (start < range.start ||
+	    start + size > range.end ||
 	    start + size < start)
 		return -ERANGE;
 
-- 
2.20.1