linux-kernel - [PATCH v2 0/8] smaps / mm/gup: fix gup_can_follow

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Message-ID: <20230801124844.278698-1-david@redhat.com>
Date:   Tue,  1 Aug 2023 14:48:36 +0200
From:   David Hildenbrand <david@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     linux-mm@...ck.org, linux-fsdevel@...r.kernel.org,
        kvm@...r.kernel.org, linux-kselftest@...r.kernel.org,
        David Hildenbrand <david@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        liubo <liubo254@...wei.com>, Peter Xu <peterx@...hat.com>,
        Matthew Wilcox <willy@...radead.org>,
        Hugh Dickins <hughd@...gle.com>,
        Jason Gunthorpe <jgg@...pe.ca>,
        John Hubbard <jhubbard@...dia.com>,
        Mel Gorman <mgorman@...e.de>, Shuah Khan <shuah@...nel.org>,
        Paolo Bonzini <pbonzini@...hat.com>
Subject: [PATCH v2 0/8] smaps / mm/gup: fix gup_can_follow_protnone fallout

This is agains mm/mm-unstable, but everything except patch #7 and #8
should apply on current master. Especially patch #1 and #2 should go
upstream first, so we can let the other stuff mature a bit longer.

Next attempt to handle the fallout of 474098edac26
("mm/gup: replace FOLL_NUMA by gup_can_follow_protnone()") where I
accidentially missed that follow_page() and smaps implicitly kept the
FOLL_NUMA flag clear by not setting it if FOLL_FORCE is absent, to
not trigger faults on PROT_NONE-mapped PTEs.

Patch #1 fixes the known issues by reintroducing FOLL_NUMA as
FOLL_HONOR_NUMA_FAULT and decoupling it from FOLL_FORCE.

Patch #2 is a cleanup that I think actually fixes some corner cases, so
I added a Fixes: tag.

Patch #3 makes KVM explicitly set FOLL_HONOR_NUMA_FAULT in the single
case where it is required, and documents the situation.

Patch #4 then stops implicitly setting FOLL_HONOR_NUMA_FAULT. But note that
for FOLL_WRITE we always implicitly honor NUMA hinting faults.

Patch #5 and patch #6 cleanup some comments.

Patch #7 improves the KVM functional tests such that patch #8 can
actually check for one of the known issues: KSM no longer working on
PROT_NONE mappings on x86-64 with CONFIG_NUMA_BALANCING.

Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: liubo <liubo254@...wei.com>
Cc: Peter Xu <peterx@...hat.com>
Cc: Matthew Wilcox <willy@...radead.org>
Cc: Hugh Dickins <hughd@...gle.com>
Cc: Jason Gunthorpe <jgg@...pe.ca>
Cc: John Hubbard <jhubbard@...dia.com>
Cc: Mel Gorman <mgorman@...e.de>
Cc: Shuah Khan <shuah@...nel.org>
Cc: Paolo Bonzini <pbonzini@...hat.com>

David Hildenbrand (8):
  mm/gup: reintroduce FOLL_NUMA as FOLL_HONOR_NUMA_FAULT
  smaps: use vm_normal_page_pmd() instead of follow_trans_huge_pmd()
  kvm: explicitly set FOLL_HONOR_NUMA_FAULT in hva_to_pfn_slow()
  mm/gup: don't implicitly set FOLL_HONOR_NUMA_FAULT
  pgtable: improve pte_protnone() comment
  mm/huge_memory: remove stale NUMA hinting comment from
    follow_trans_huge_pmd()
  selftest/mm: ksm_functional_tests: test in mmap_and_merge_range() if
    anything got merged
  selftest/mm: ksm_functional_tests: Add PROT_NONE test

 fs/proc/task_mmu.c                            |   3 +-
 include/linux/mm.h                            |  21 +++-
 include/linux/mm_types.h                      |   9 ++
 include/linux/pgtable.h                       |  16 ++-
 mm/gup.c                                      |  23 +++-
 mm/huge_memory.c                              |   3 +-
 .../selftests/mm/ksm_functional_tests.c       | 106 ++++++++++++++++--
 virt/kvm/kvm_main.c                           |  13 ++-
 8 files changed, 164 insertions(+), 30 deletions(-)

-- 
2.41.0