arm64: mm: Use READ_ONCE/WRITE_ONCE when accessing page tables
authorWill Deacon <will.deacon@arm.com>
Thu, 15 Feb 2018 11:14:56 +0000 (11:14 +0000)
committerCatalin Marinas <catalin.marinas@arm.com>
Fri, 16 Feb 2018 18:13:57 +0000 (18:13 +0000)
commit20a004e7b017cce282a46ac5d02c2b9c6b9bb1fa
tree390bf8546ee581e54103e2bdc5876ac56cceefca
parent2ce77f6d8a9ae9ce6d80397d88bdceb84a2004cd
arm64: mm: Use READ_ONCE/WRITE_ONCE when accessing page tables

In many cases, page tables can be accessed concurrently by either another
CPU (due to things like fast gup) or by the hardware page table walker
itself, which may set access/dirty bits. In such cases, it is important
to use READ_ONCE/WRITE_ONCE when accessing page table entries so that
entries cannot be torn, merged or subject to apparent loss of coherence
due to compiler transformations.

Whilst there are some scenarios where this cannot happen (e.g. pinned
kernel mappings for the linear region), the overhead of using READ_ONCE
/WRITE_ONCE everywhere is minimal and makes the code an awful lot easier
to reason about. This patch consistently uses these macros in the arch
code, as well as explicitly namespacing pointers to page table entries
from the entries themselves by using adopting a 'p' suffix for the former
(as is sometimes used elsewhere in the kernel source).

Tested-by: Yury Norov <ynorov@caviumnetworks.com>
Tested-by: Richard Ruigrok <rruigrok@codeaurora.org>
Reviewed-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
13 files changed:
arch/arm64/include/asm/hugetlb.h
arch/arm64/include/asm/kvm_mmu.h
arch/arm64/include/asm/mmu_context.h
arch/arm64/include/asm/pgalloc.h
arch/arm64/include/asm/pgtable.h
arch/arm64/kernel/efi.c
arch/arm64/kernel/hibernate.c
arch/arm64/mm/dump.c
arch/arm64/mm/fault.c
arch/arm64/mm/hugetlbpage.c
arch/arm64/mm/kasan_init.c
arch/arm64/mm/mmu.c
arch/arm64/mm/pageattr.c