We need to limit the max memory based on Linux page table format.
Add checks to limit memory based on pte size. Also limit the memory
based on MAX_PHSYSMEM_BITS.
Signed-off-by: Aneesh Kumar K.V <aneesh.ku...@linux.vnet.ibm.com>
---
Changes from V1:
* Update commit message. 4K can handle 64TB
* Also limit based on MAX_PHSYSMEM_BITS
arch/powerpc/include/asm/mmu.h | 8 ++++++++
arch/powerpc/include/asm/sparsemem.h | 2 --
arch/powerpc/kernel/prom.c | 25 ++++++++++++++++++++++---
3 files changed, 30 insertions(+), 5 deletions(-)
diff --git a/arch/powerpc/include/asm/mmu.h b/arch/powerpc/include/asm/mmu.h
index 3d5abfe6ba67..d44d49093c8d 100644
--- a/arch/powerpc/include/asm/mmu.h
+++ b/arch/powerpc/include/asm/mmu.h
@@ -200,6 +200,14 @@ static inline void assert_pte_locked(struct mm_struct *mm,
unsigned long addr)
# include <asm/mmu-8xx.h>
#endif
+#ifdef CONFIG_PHYS_64BIT
+/*
+ * Max supported memory on 64bit system is 64TB.
+ */
+#define MAX_PHYSMEM_BITS 46
+#else
+#define MAX_PHYSMEM_BITS 32
+#endif
#endif /* __KERNEL__ */
#endif /* _ASM_POWERPC_MMU_H_ */
diff --git a/arch/powerpc/include/asm/sparsemem.h
b/arch/powerpc/include/asm/sparsemem.h
index f6fc0ee813d7..fc3808378893 100644
--- a/arch/powerpc/include/asm/sparsemem.h
+++ b/arch/powerpc/include/asm/sparsemem.h
@@ -11,8 +11,6 @@
#define SECTION_SIZE_BITS 24
#define MAX_PHYSADDR_BITS 46
-#define MAX_PHYSMEM_BITS 46
-
#endif /* CONFIG_SPARSEMEM */
#ifdef CONFIG_MEMORY_HOTPLUG
diff --git a/arch/powerpc/kernel/prom.c b/arch/powerpc/kernel/prom.c
index 308c5e15676b..c09315b32ca7 100644
--- a/arch/powerpc/kernel/prom.c
+++ b/arch/powerpc/kernel/prom.c
@@ -698,9 +698,28 @@ void __init early_init_devtree(void *params)
#endif
reserve_crashkernel();
early_reserve_mem();
-
- /* Ensure that total memory size is page-aligned. */
- limit = ALIGN(memory_limit ?: memblock_phys_mem_size(), PAGE_SIZE);
+ /*
+ * if not specified limit the memory based on the pfn count that
+ * we can fit in pte_t. Also ensure that total memory size is
+ * page-aligned.
+ */
+ if (!memory_limit) {
+ int bit_count;
+ phys_addr_t pte_mem_limit;
+
+ limit = memblock_phys_mem_size();
+ if (limit >= (1ULL << MAX_PHYSMEM_BITS))
+ limit = (1ULL << MAX_PHYSMEM_BITS) - 1;
+
+ BUILD_BUG_ON(sizeof(pte_basic_t) > 8);
+ bit_count = (sizeof(pte_basic_t) * 8) - PTE_RPN_SHIFT +
PAGE_SHIFT;
+ pte_mem_limit = ~0ULL >> (64 - bit_count);
+ if (limit > pte_mem_limit)
+ limit = pte_mem_limit;
+ } else
+ limit = memory_limit;
+
+ limit = ALIGN(limit, PAGE_SIZE);
memblock_enforce_memory_limit(limit);
memblock_allow_resize();
--
2.1.4
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