vma->vm_flags is an 'unsigned long', so has space for 32 flags on 32-bit architectures. The high 32 bits are unused on 64-bit platforms. We've steered away from using the unused high VMA bits for things because we would have difficulty supporting it on 32-bit. Protection Keys are not available in 32-bit mode, so there is no concern about supporting this feature in 32-bit mode or on 32-bit CPUs. This patch carves out 4 bits from the high half of vma->vm_flags and allows architectures to set config option to make them available. Sparse complains about these constants unless we explicitly call them "UL". --- b/arch/x86/Kconfig | 1 + b/include/linux/mm.h | 7 +++++++ b/mm/Kconfig | 3 +++ 3 files changed, 11 insertions(+) diff -puN arch/x86/Kconfig~pkeys-07-eat-high-vma-flags arch/x86/Kconfig --- a/arch/x86/Kconfig~pkeys-07-eat-high-vma-flags 2015-09-16 10:48:14.638118972 -0700 +++ b/arch/x86/Kconfig 2015-09-16 10:48:14.646119334 -0700 @@ -152,6 +152,7 @@ config X86 select VIRT_TO_BUS select X86_DEV_DMA_OPS if X86_64 select X86_FEATURE_NAMES if PROC_FS + select ARCH_USES_HIGH_VMA_FLAGS if X86_INTEL_MEMORY_PROTECTION_KEYS config INSTRUCTION_DECODER def_bool y diff -puN include/linux/mm.h~pkeys-07-eat-high-vma-flags include/linux/mm.h --- a/include/linux/mm.h~pkeys-07-eat-high-vma-flags 2015-09-16 10:48:14.640119062 -0700 +++ b/include/linux/mm.h 2015-09-16 10:48:14.647119380 -0700 @@ -157,6 +157,13 @@ extern unsigned int kobjsize(const void #define VM_NOHUGEPAGE 0x40000000 /* MADV_NOHUGEPAGE marked this vma */ #define VM_MERGEABLE 0x80000000 /* KSM may merge identical pages */ +#ifdef CONFIG_ARCH_USES_HIGH_VMA_FLAGS +#define VM_HIGH_ARCH_0 0x100000000UL /* bit only usable on 64-bit architectures */ +#define VM_HIGH_ARCH_1 0x200000000UL /* bit only usable on 64-bit architectures */ +#define VM_HIGH_ARCH_2 0x400000000UL /* bit only usable on 64-bit architectures */ +#define VM_HIGH_ARCH_3 0x800000000UL /* bit only usable on 64-bit architectures */ +#endif /* CONFIG_ARCH_USES_HIGH_VMA_FLAGS */ + #if defined(CONFIG_X86) # define VM_PAT VM_ARCH_1 /* PAT reserves whole VMA at once (x86) */ #elif defined(CONFIG_PPC) diff -puN mm/Kconfig~pkeys-07-eat-high-vma-flags mm/Kconfig --- a/mm/Kconfig~pkeys-07-eat-high-vma-flags 2015-09-16 10:48:14.642119153 -0700 +++ b/mm/Kconfig 2015-09-16 10:48:14.647119380 -0700 @@ -680,3 +680,6 @@ config ZONE_DEVICE config FRAME_VECTOR bool + +config ARCH_USES_HIGH_VMA_FLAGS + bool _ -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>