Hi, David, What is the opposite of exclusive here? Shared or inclusive? I prefer pte_swp_mkshared() or pte_swp_mkinclusive() rather than pte_swp_clear_exclusive(). Existing examples: dirty/clean, young/old ... Huacai On Tue, Dec 6, 2022 at 10:48 PM David Hildenbrand <david@xxxxxxxxxx> wrote: > > This is the follow-up on [1]: > [PATCH v2 0/8] mm: COW fixes part 3: reliable GUP R/W FOLL_GET of > anonymous pages > > After we implemented __HAVE_ARCH_PTE_SWP_EXCLUSIVE on most prominent > enterprise architectures, implement __HAVE_ARCH_PTE_SWP_EXCLUSIVE on all > remaining architectures that support swap PTEs. > > This makes sure that exclusive anonymous pages will stay exclusive, even > after they were swapped out -- for example, making GUP R/W FOLL_GET of > anonymous pages reliable. Details can be found in [1]. > > This primarily fixes remaining known O_DIRECT memory corruptions that can > happen on concurrent swapout, whereby we can lose DMA reads to a page > (modifying the user page by writing to it). > > To verify, there are two test cases (requiring swap space, obviously): > (1) The O_DIRECT+swapout test case [2] from Andrea. This test case tries > triggering a race condition. > (2) My vmsplice() test case [3] that tries to detect if the exclusive > marker was lost during swapout, not relying on a race condition. > > > For example, on 32bit x86 (with and without PAE), my test case fails > without these patches: > $ ./test_swp_exclusive > FAIL: page was replaced during COW > But succeeds with these patches: > $ ./test_swp_exclusive > PASS: page was not replaced during COW > > > Why implement __HAVE_ARCH_PTE_SWP_EXCLUSIVE for all architectures, even > the ones where swap support might be in a questionable state? This is the > first step towards removing "readable_exclusive" migration entries, and > instead using pte_swp_exclusive() also with (readable) migration entries > instead (as suggested by Peter). The only missing piece for that is > supporting pmd_swp_exclusive() on relevant architectures with THP > migration support. > > As all relevant architectures now implement __HAVE_ARCH_PTE_SWP_EXCLUSIVE,, > we can drop __HAVE_ARCH_PTE_SWP_EXCLUSIVE in the last patch. > > > RFC because some of the swap PTE layouts are really tricky and I really > need some feedback related to deciphering these layouts and "using yet > unused PTE bits in swap PTEs". I tried cross-compiling all relevant setups > (phew, I might only miss some power/nohash variants), but only tested on > x86 so far. > > CCing arch maintainers only on this cover letter and on the respective > patch(es). > > > [1] https://lkml.kernel.org/r/20220329164329.208407-1-david@xxxxxxxxxx > [2] https://gitlab.com/aarcange/kernel-testcases-for-v5.11/-/blob/main/page_count_do_wp_page-swap.c > [3] https://gitlab.com/davidhildenbrand/scratchspace/-/blob/main/test_swp_exclusive.c > > David Hildenbrand (26): > mm/debug_vm_pgtable: more pte_swp_exclusive() sanity checks > alpha/mm: support __HAVE_ARCH_PTE_SWP_EXCLUSIVE > arc/mm: support __HAVE_ARCH_PTE_SWP_EXCLUSIVE > arm/mm: support __HAVE_ARCH_PTE_SWP_EXCLUSIVE > csky/mm: support __HAVE_ARCH_PTE_SWP_EXCLUSIVE > hexagon/mm: support __HAVE_ARCH_PTE_SWP_EXCLUSIVE > ia64/mm: support __HAVE_ARCH_PTE_SWP_EXCLUSIVE > loongarch/mm: support __HAVE_ARCH_PTE_SWP_EXCLUSIVE > m68k/mm: remove dummy __swp definitions for nommu > m68k/mm: support __HAVE_ARCH_PTE_SWP_EXCLUSIVE > microblaze/mm: support __HAVE_ARCH_PTE_SWP_EXCLUSIVE > mips/mm: support __HAVE_ARCH_PTE_SWP_EXCLUSIVE > nios2/mm: refactor swap PTE layout > nios2/mm: support __HAVE_ARCH_PTE_SWP_EXCLUSIVE > openrisc/mm: support __HAVE_ARCH_PTE_SWP_EXCLUSIVE > parisc/mm: support __HAVE_ARCH_PTE_SWP_EXCLUSIVE > powerpc/mm: support __HAVE_ARCH_PTE_SWP_EXCLUSIVE on 32bit book3s > powerpc/nohash/mm: support __HAVE_ARCH_PTE_SWP_EXCLUSIVE > riscv/mm: support __HAVE_ARCH_PTE_SWP_EXCLUSIVE > sh/mm: support __HAVE_ARCH_PTE_SWP_EXCLUSIVE > sparc/mm: support __HAVE_ARCH_PTE_SWP_EXCLUSIVE on 32bit > sparc/mm: support __HAVE_ARCH_PTE_SWP_EXCLUSIVE on 64bit > um/mm: support __HAVE_ARCH_PTE_SWP_EXCLUSIVE > x86/mm: support __HAVE_ARCH_PTE_SWP_EXCLUSIVE also on 32bit > xtensa/mm: support __HAVE_ARCH_PTE_SWP_EXCLUSIVE > mm: remove __HAVE_ARCH_PTE_SWP_EXCLUSIVE > > arch/alpha/include/asm/pgtable.h | 40 ++++++++- > arch/arc/include/asm/pgtable-bits-arcv2.h | 26 +++++- > arch/arm/include/asm/pgtable-2level.h | 3 + > arch/arm/include/asm/pgtable-3level.h | 3 + > arch/arm/include/asm/pgtable.h | 34 ++++++-- > arch/arm64/include/asm/pgtable.h | 1 - > arch/csky/abiv1/inc/abi/pgtable-bits.h | 13 ++- > arch/csky/abiv2/inc/abi/pgtable-bits.h | 19 ++-- > arch/csky/include/asm/pgtable.h | 17 ++++ > arch/hexagon/include/asm/pgtable.h | 36 ++++++-- > arch/ia64/include/asm/pgtable.h | 31 ++++++- > arch/loongarch/include/asm/pgtable-bits.h | 4 + > arch/loongarch/include/asm/pgtable.h | 38 +++++++- > arch/m68k/include/asm/mcf_pgtable.h | 35 +++++++- > arch/m68k/include/asm/motorola_pgtable.h | 37 +++++++- > arch/m68k/include/asm/pgtable_no.h | 6 -- > arch/m68k/include/asm/sun3_pgtable.h | 38 +++++++- > arch/microblaze/include/asm/pgtable.h | 44 +++++++--- > arch/mips/include/asm/pgtable-32.h | 86 ++++++++++++++++--- > arch/mips/include/asm/pgtable-64.h | 23 ++++- > arch/mips/include/asm/pgtable.h | 35 ++++++++ > arch/nios2/include/asm/pgtable-bits.h | 3 + > arch/nios2/include/asm/pgtable.h | 37 ++++++-- > arch/openrisc/include/asm/pgtable.h | 40 +++++++-- > arch/parisc/include/asm/pgtable.h | 40 ++++++++- > arch/powerpc/include/asm/book3s/32/pgtable.h | 37 ++++++-- > arch/powerpc/include/asm/book3s/64/pgtable.h | 1 - > arch/powerpc/include/asm/nohash/32/pgtable.h | 22 +++-- > arch/powerpc/include/asm/nohash/32/pte-40x.h | 6 +- > arch/powerpc/include/asm/nohash/32/pte-44x.h | 18 +--- > arch/powerpc/include/asm/nohash/32/pte-85xx.h | 4 +- > arch/powerpc/include/asm/nohash/64/pgtable.h | 24 +++++- > arch/powerpc/include/asm/nohash/pgtable.h | 15 ++++ > arch/powerpc/include/asm/nohash/pte-e500.h | 1 - > arch/riscv/include/asm/pgtable-bits.h | 3 + > arch/riscv/include/asm/pgtable.h | 28 ++++-- > arch/s390/include/asm/pgtable.h | 1 - > arch/sh/include/asm/pgtable_32.h | 53 +++++++++--- > arch/sparc/include/asm/pgtable_32.h | 26 +++++- > arch/sparc/include/asm/pgtable_64.h | 37 +++++++- > arch/sparc/include/asm/pgtsrmmu.h | 14 +-- > arch/um/include/asm/pgtable.h | 36 +++++++- > arch/x86/include/asm/pgtable-2level.h | 26 ++++-- > arch/x86/include/asm/pgtable-3level.h | 26 +++++- > arch/x86/include/asm/pgtable.h | 3 - > arch/xtensa/include/asm/pgtable.h | 31 +++++-- > include/linux/pgtable.h | 29 ------- > mm/debug_vm_pgtable.c | 25 +++++- > mm/memory.c | 4 - > mm/rmap.c | 11 --- > 50 files changed, 943 insertions(+), 227 deletions(-) > > -- > 2.38.1 > >
