[v3,0/7] smaps / mm/gup: fix gup_can_follow_protnone fallout

Message

David Hildenbrand Aug. 3, 2023, 2:32 p.m. UTC

This is agains mm/mm-unstable, but everything except patch #6 and #7
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.


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 cleans up a comments.

Patch #6 improves the KVM functional tests such that patch #7 can
actually check for one of the known issues: KSM no longer working on
PROT_NONE mappings on x86-64 with CONFIG_NUMA_BALANCING.

v2 -> V3:
* "mm/gup: reintroduce FOLL_NUMA as FOLL_HONOR_NUMA_FAULT"
 -> Squash one comment removal
 -> Adjust the KSM comment
* smaps: use vm_normal_page_pmd() instead of follow_trans_huge_pmd()
 -> Move follow_trans_huge_pmd() to mm/internal.h

Cc: Andrew Morton <[e-mail]>
Cc: Linus Torvalds <[e-mail]>
Cc: liubo <[e-mail]>
Cc: Peter Xu <[e-mail]>
Cc: Matthew Wilcox <[e-mail]>
Cc: Hugh Dickins <[e-mail]>
Cc: Jason Gunthorpe <[e-mail]>
Cc: John Hubbard <[e-mail]>
Cc: Mel Gorman <[e-mail]>
Cc: Shuah Khan <[e-mail]>
Cc: Paolo Bonzini <[e-mail]>

David Hildenbrand (7):
  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
  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/huge_mm.h                       |   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 +-
 mm/internal.h                                 |   7 ++
 .../selftests/mm/ksm_functional_tests.c       | 106 ++++++++++++++++--
 virt/kvm/kvm_main.c                           |  13 ++-
 10 files changed, 171 insertions(+), 33 deletions(-)