x86, mm: limit MAXMEM on 64-bit

on 64-bit x86 the physical memory limit is controlled by the sparsemem
bits - which are 44 bits right now. But MAXMEM (the max pfn number
e820 parsing will allow to enter our sizing routines) is set to
0x00003fffffffffff, i.e. 46 bits - that's too large because it overlaps
into the vmalloc range.

So couple MAXMEM to MAX_PHYSMEM_BITS, and add a comment that the
maximum of MAX_PHYSMEM_BITS is 45 bits.

Signed-off-by: Ingo Molnar <mingo@elte.hu>

2 files changed, 2 insertions, 2 deletions

diff --git a/arch/x86/include/asm/pgtable_64.h b/arch/x86/include/asm/pgtable_64.h
index 65b6be6677c7..c54ba69608bd 100644
--- a/arch/x86/include/asm/pgtable_64.h
+++ b/arch/x86/include/asm/pgtable_64.h
@@ -146,7 +146,7 @@ static inline void native_pgd_clear(pgd_t *pgd)
 #define PGDIR_MASK      (~(PGDIR_SIZE - 1))
 
 
-#define MAXMEM           _AC(0x00003fffffffffff, UL)
+#define MAXMEM           _AC(__AC(1, UL) << MAX_PHYSMEM_BITS, UL)
 #define VMALLOC_START    _AC(0xffffc20000000000, UL)
 #define VMALLOC_END      _AC(0xffffe1ffffffffff, UL)
 #define VMEMMAP_START    _AC(0xffffe20000000000, UL)
diff --git a/arch/x86/include/asm/sparsemem.h b/arch/x86/include/asm/sparsemem.h
index be44f7dab395..e3cc3c063ec5 100644
--- a/arch/x86/include/asm/sparsemem.h
+++ b/arch/x86/include/asm/sparsemem.h
@@ -27,7 +27,7 @@
 #else /* CONFIG_X86_32 */
 # define SECTION_SIZE_BITS      27 /* matt - 128 is convenient right now */
 # define MAX_PHYSADDR_BITS      44
-# define MAX_PHYSMEM_BITS       44
+# define MAX_PHYSMEM_BITS       44 /* Can be max 45 bits */
 #endif
 
 #endif /* CONFIG_SPARSEMEM */