[PATCH v2 0/8] smaps / mm/gup: fix gup_can_follow_protnone fallout

David Hildenbrand
2023-08-01T12:49:46Z

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@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: liubo <liubo254@huawei.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Paolo Bonzini <pbonzini@redhat.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