set_memory: allow querying whether set_direct_map_*() is actually enabled

2021-07-08T18:48:20Z

On arm64, set_direct_map_*() functions may return 0 without actually changing the linear map. This behaviour can be controlled using kernel parameters, so we need a way to determine at runtime whether calls to set_direct_map_invalid_noflush() and set_direct_map_default_noflush() have any effect. Extend set_memory API with can_set_direct_map() function that allows checking if calling set_direct_map_*() will actually change the page table, replace several occurrences of open coded checks in arm64 with the new function and provide a generic stub for architectures that always modify page tables upon calls to set_direct_map APIs. [arnd@arndb.de: arm64: kfence: fix header inclusion ] Link: https://lkml.kernel.org/r/20210518072034.31572-4-rppt@kernel.org Signed-off-by: Mike Rapoport Reviewed-by: Catalin Marinas Reviewed-by: David Hildenbrand Acked-by: James Bottomley Cc: Alexander Viro Cc: Andy Lutomirski Cc: Arnd Bergmann Cc: Borislav Petkov Cc: Christopher Lameter Cc: Dan Williams Cc: Dave Hansen Cc: Elena Reshetova Cc: Hagen Paul Pfeifer Cc: "H. Peter Anvin" Cc: Ingo Molnar Cc: James Bottomley Cc: "Kirill A. Shutemov" Cc: Mark Rutland Cc: Matthew Wilcox Cc: Michael Kerrisk Cc: Palmer Dabbelt Cc: Palmer Dabbelt Cc: Paul Walmsley Cc: Peter Zijlstra Cc: Rick Edgecombe Cc: Roman Gushchin Cc: Shakeel Butt Cc: Shuah Khan Cc: Thomas Gleixner Cc: Tycho Andersen Cc: Will Deacon Cc: kernel test robot Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

kernel/arch/arm64/include/asm/set_memory.h, branch linux-6.2.y

set_memory: allow querying whether set_direct_map_*() is actually enabled