[PATCH] arm64: mm: Fix memmap to be initialized for the entire section

[Robert Richter]

There is a memory setup problem on ThunderX systems with certain
memory configurations. The symptom is

 kernel BUG at mm/page_alloc.c:1848!

This happens for some configs with 64k page size enabled. The bug
triggers for page zones with some pages in the zone not assigned to
this particular zone. In my case some pages that are marked as nomap
were not reassigned to the new zone of node 1, so those are still
assigned to node 0.

The reason for the mis-configuration is a change in pfn_valid() which
reports pages marked nomap as invalid:

 68709f45385a arm64: only consider memblocks with NOMAP cleared for linear mapping

This causes pages marked as nomap being no long reassigned to the new
zone in memmap_init_zone() by calling __init_single_pfn().

Fixing this by restoring the old behavior of pfn_valid() to use
memblock_is_memory(). Also changing users of pfn_valid() in arm64 code
to use memblock_is_map_memory() where necessary. This only affects
code in ioremap.c. The code in mmu.c still can use the new version of
pfn_valid().

Should be marked stable v4.5..

Signed-off-by: Robert Richter <rrichter at cavium.com>
---
 arch/arm64/mm/init.c    | 2 +-
 arch/arm64/mm/ioremap.c | 5 +++--
 2 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
index bbb7ee76e319..25b8659c2a9f 100644
--- a/arch/arm64/mm/init.c
+++ b/arch/arm64/mm/init.c
@@ -147,7 +147,7 @@ static void __init zone_sizes_init(unsigned long min, unsigned long max)
 #ifdef CONFIG_HAVE_ARCH_PFN_VALID
 int pfn_valid(unsigned long pfn)
 {
-	return memblock_is_map_memory(pfn << PAGE_SHIFT);
+	return memblock_is_memory(pfn << PAGE_SHIFT);
 }
 EXPORT_SYMBOL(pfn_valid);
 #endif
diff --git a/arch/arm64/mm/ioremap.c b/arch/arm64/mm/ioremap.c
index 01e88c8bcab0..c17c220b0c48 100644
--- a/arch/arm64/mm/ioremap.c
+++ b/arch/arm64/mm/ioremap.c
@@ -21,6 +21,7 @@
  */
 
 #include <linux/export.h>
+#include <linux/memblock.h>
 #include <linux/mm.h>
 #include <linux/vmalloc.h>
 #include <linux/io.h>
@@ -55,7 +56,7 @@ static void __iomem *__ioremap_caller(phys_addr_t phys_addr, size_t size,
 	/*
 	 * Don't allow RAM to be mapped.
 	 */
-	if (WARN_ON(pfn_valid(__phys_to_pfn(phys_addr))))
+	if (WARN_ON(memblock_is_map_memory(phys_addr)))
 		return NULL;
 
 	area = get_vm_area_caller(size, VM_IOREMAP, caller);
@@ -96,7 +97,7 @@ EXPORT_SYMBOL(__iounmap);
 void __iomem *ioremap_cache(phys_addr_t phys_addr, size_t size)
 {
 	/* For normal memory we already have a cacheable mapping. */
-	if (pfn_valid(__phys_to_pfn(phys_addr)))
+	if (memblock_is_map_memory(phys_addr))
 		return (void __iomem *)__phys_to_virt(phys_addr);
 
 	return __ioremap_caller(phys_addr, size, __pgprot(PROT_NORMAL),
-- 
2.7.0.rc3