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Message-ID: <CAAhV-H4bU7JnAPyf9Mv1m+WGR5NWmHJLva3d9_CsRd4Q_OHVpg@mail.gmail.com>
Date:   Sun, 18 Dec 2022 11:32:59 +0800
From:   Huacai Chen <chenhuacai@...nel.org>
To:     David Hildenbrand <david@...hat.com>
Cc:     linux-kernel@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Hugh Dickins <hughd@...gle.com>,
        John Hubbard <jhubbard@...dia.com>,
        Jason Gunthorpe <jgg@...dia.com>,
        Mike Rapoport <rppt@...ux.ibm.com>,
        Yang Shi <shy828301@...il.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Nadav Amit <namit@...are.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Peter Xu <peterx@...hat.com>, linux-mm@...ck.org,
        x86@...nel.org, linux-alpha@...r.kernel.org,
        linux-snps-arc@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-csky@...r.kernel.org,
        linux-hexagon@...r.kernel.org, linux-ia64@...r.kernel.org,
        loongarch@...ts.linux.dev, linux-m68k@...ts.linux-m68k.org,
        linux-mips@...r.kernel.org, openrisc@...ts.librecores.org,
        linux-parisc@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        linux-riscv@...ts.infradead.org, linux-s390@...r.kernel.org,
        linux-sh@...r.kernel.org, sparclinux@...r.kernel.org,
        linux-um@...ts.infradead.org, linux-xtensa@...ux-xtensa.org,
        Albert Ou <aou@...s.berkeley.edu>,
        Anton Ivanov <anton.ivanov@...bridgegreys.com>,
        Borislav Petkov <bp@...en8.de>, Brian Cain <bcain@...cinc.com>,
        Christophe Leroy <christophe.leroy@...roup.eu>,
        Chris Zankel <chris@...kel.net>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "David S. Miller" <davem@...emloft.net>,
        Dinh Nguyen <dinguyen@...nel.org>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Greg Ungerer <gerg@...ux-m68k.org>,
        Guo Ren <guoren@...nel.org>, Helge Deller <deller@....de>,
        "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
        Ivan Kokshaysky <ink@...assic.park.msu.ru>,
        "James E.J. Bottomley" <James.Bottomley@...senpartnership.com>,
        Johannes Berg <johannes@...solutions.net>,
        Matt Turner <mattst88@...il.com>,
        Max Filippov <jcmvbkbc@...il.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Michal Simek <monstr@...str.eu>,
        Nicholas Piggin <npiggin@...il.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Richard Henderson <richard.henderson@...aro.org>,
        Richard Weinberger <richard@....at>,
        Rich Felker <dalias@...c.org>,
        Russell King <linux@...linux.org.uk>,
        Stafford Horne <shorne@...il.com>,
        Stefan Kristiansson <stefan.kristiansson@...nalahti.fi>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        Vineet Gupta <vgupta@...nel.org>,
        WANG Xuerui <kernel@...0n.name>,
        Yoshinori Sato <ysato@...rs.sourceforge.jp>
Subject: Re: [PATCH mm-unstable RFC 00/26] mm: support __HAVE_ARCH_PTE_SWP_EXCLUSIVE
 on all architectures with swap PTEs

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@...hat.com> 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@redhat.com
> [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
>
>

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