This #define is not used anywhere, and has the wrong value on x86_64. I tried digging into the history a bit, but it seems to have been unused even in the initial merge of sparsemem in v2.6.13, when it was first defined. Arvind Sankar (3): x86/mm: Drop unused MAX_PHYSADDR_BITS sh/mm: Drop unused MAX_PHYSADDR_BITS sparc: Drop unused MAX_PHYSADDR_BITS arch/sh/include/asm/sparsemem.h | 4 +--- arch/sparc/include/asm/sparsemem.h | 1 - arch/x86/include/asm/sparsemem.h | 6 +----- 3 files changed, 2 insertions(+), 9 deletions(-) -- 2.26.2