linux-kernel - Re: [RFC PATCH v2 2/3] mm: make pXd_addr_end() functions page-table entry aware

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Date:   Tue, 8 Sep 2020 07:14:38 +0200
From:   Christophe Leroy <christophe.leroy@...roup.eu>
To:     Gerald Schaefer <gerald.schaefer@...ux.ibm.com>,
        Jason Gunthorpe <jgg@...pe.ca>,
        John Hubbard <jhubbard@...dia.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        linux-mm <linux-mm@...ck.org>, Paul Mackerras <paulus@...ba.org>,
        linux-sparc <sparclinux@...r.kernel.org>,
        Alexander Gordeev <agordeev@...ux.ibm.com>,
        Claudio Imbrenda <imbrenda@...ux.ibm.com>,
        Will Deacon <will@...nel.org>,
        linux-arch <linux-arch@...r.kernel.org>,
        linux-s390 <linux-s390@...r.kernel.org>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Richard Weinberger <richard@....at>,
        linux-x86 <x86@...nel.org>, Russell King <linux@...linux.org.uk>,
        Christian Borntraeger <borntraeger@...ibm.com>,
        Ingo Molnar <mingo@...hat.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Heiko Carstens <hca@...ux.ibm.com>,
        Arnd Bergmann <arnd@...db.de>, Jeff Dike <jdike@...toit.com>,
        linux-um <linux-um@...ts.infradead.org>,
        Borislav Petkov <bp@...en8.de>,
        Andy Lutomirski <luto@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-arm <linux-arm-kernel@...ts.infradead.org>,
        linux-power <linuxppc-dev@...ts.ozlabs.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Mike Rapoport <rppt@...nel.org>
Subject: Re: [RFC PATCH v2 2/3] mm: make pXd_addr_end() functions page-table
 entry aware



Le 07/09/2020 à 20:00, Gerald Schaefer a écrit :
> From: Alexander Gordeev <agordeev@...ux.ibm.com>
> 
> Unlike all other page-table abstractions pXd_addr_end() do not take
> into account a particular table entry in which context the functions
> are called. On architectures with dynamic page-tables folding that
> might lead to lack of necessary information that is difficult to
> obtain other than from the table entry itself. That already led to
> a subtle memory corruption issue on s390.
> 
> By letting pXd_addr_end() functions know about the page-table entry
> we allow archs not only make extra checks, but also optimizations.
> 
> As result of this change the pXd_addr_end_folded() functions used
> in gup_fast traversal code become unnecessary and get replaced with
> universal pXd_addr_end() variants.
> 
> The arch-specific updates not only add dereferencing of page-table
> entry pointers, but also small changes to the code flow to make those
> dereferences possible, at least for x86 and powerpc. Also for arm64,
> but in way that should not have any impact.
> 

[...]

> 
> Signed-off-by: Alexander Gordeev <agordeev@...ux.ibm.com>
> Signed-off-by: Gerald Schaefer <gerald.schaefer@...ux.ibm.com>
> ---
>   arch/arm/include/asm/pgtable-2level.h    |  2 +-
>   arch/arm/mm/idmap.c                      |  6 ++--
>   arch/arm/mm/mmu.c                        |  8 ++---
>   arch/arm64/kernel/hibernate.c            | 16 ++++++----
>   arch/arm64/kvm/mmu.c                     | 16 +++++-----
>   arch/arm64/mm/kasan_init.c               |  8 ++---
>   arch/arm64/mm/mmu.c                      | 25 +++++++--------
>   arch/powerpc/mm/book3s64/radix_pgtable.c |  7 ++---
>   arch/powerpc/mm/hugetlbpage.c            |  6 ++--

You forgot arch/powerpc/mm/book3s64/subpage_prot.c it seems.

>   arch/s390/include/asm/pgtable.h          |  8 ++---
>   arch/s390/mm/page-states.c               |  8 ++---
>   arch/s390/mm/pageattr.c                  |  8 ++---
>   arch/s390/mm/vmem.c                      |  8 ++---
>   arch/sparc/mm/hugetlbpage.c              |  6 ++--
>   arch/um/kernel/tlb.c                     |  8 ++---
>   arch/x86/mm/init_64.c                    | 15 ++++-----
>   arch/x86/mm/kasan_init_64.c              | 16 +++++-----
>   include/asm-generic/pgtable-nop4d.h      |  2 +-
>   include/asm-generic/pgtable-nopmd.h      |  2 +-
>   include/asm-generic/pgtable-nopud.h      |  2 +-
>   include/linux/pgtable.h                  | 26 ++++-----------
>   mm/gup.c                                 |  8 ++---
>   mm/ioremap.c                             |  8 ++---
>   mm/kasan/init.c                          | 17 +++++-----
>   mm/madvise.c                             |  4 +--
>   mm/memory.c                              | 40 ++++++++++++------------
>   mm/mlock.c                               | 18 ++++++++---
>   mm/mprotect.c                            |  8 ++---
>   mm/pagewalk.c                            |  8 ++---
>   mm/swapfile.c                            |  8 ++---
>   mm/vmalloc.c                             | 16 +++++-----
>   31 files changed, 165 insertions(+), 173 deletions(-)

Christophe