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

From: David Hildenbrand
Date: Thu Aug 03 2023 - 10:33:07 EST


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 <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: liubo <liubo254@xxxxxxxxxx>
Cc: Peter Xu <peterx@xxxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Jason Gunthorpe <jgg@xxxxxxxx>
Cc: John Hubbard <jhubbard@xxxxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxx>
Cc: Shuah Khan <shuah@xxxxxxxxxx>
Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>

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(-)

--
2.41.0