[RFC PATCH 0/2] Add flag as THP allocation hint for memfd_restricted() syscall

[Ackerley Tng]

Hello,

This patchset builds upon the memfd_restricted() system call that has
been discussed in the ‘KVM: mm: fd-based approach for supporting KVM’
patch series, at
https://lore.kernel.org/lkml/20221202061347.1070246-1-chao.p.peng@xxxxxxxxxxxxxxx/T/#m7e944d7892afdd1d62a03a287bd488c56e377b0c

The tree can be found at:
https://github.com/googleprodkernel/linux-cc/tree/restrictedmem-rmfd-hugepage

Following the RFC to provide mount for memfd_restricted() syscall at
https://lore.kernel.org/lkml/cover.1676507663.git.ackerleytng@xxxxxxxxxx/T/#u,
this patchset adds the RMFD_HUGEPAGE flag to the memfd_restricted()
syscall, which will hint the kernel to use Transparent HugePages to
back restrictedmem pages.

This supplements the interface proposed earlier, which requires the
creation of a tmpfs mount to be passed to memfd_restricted(), with a
more direct per-file hint.

Dependencies:

+ Sean’s iteration of the ‘KVM: mm: fd-based approach for supporting
  KVM’ patch series at
  https://github.com/sean-jc/linux/tree/x86/upm_base_support
+ Proposed fix for restrictedmem_getattr() as mentioned on the mailing
  list at
  https://lore.kernel.org/lkml/diqzzga0fv96.fsf@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/
+ Hugh’s patch:
  https://lore.kernel.org/lkml/c140f56a-1aa3-f7ae-b7d1-93da7d5a3572@xxxxxxxxxx/,
  which provides functionality in shmem that reads the VM_HUGEPAGE
  flag in key functions shmem_is_huge() and shmem_get_inode()

Future work/TODOs:
+ man page for the memfd_restricted() syscall
+ Support for per file NUMA binding hints

Ackerley Tng (2):
  mm: restrictedmem: Add flag as THP allocation hint for
    memfd_restricted() syscall
  selftests: restrictedmem: Add selftest for RMFD_HUGEPAGE

 include/uapi/linux/restrictedmem.h            |  1 +
 mm/restrictedmem.c                            | 27 ++++++++++++-------
 .../restrictedmem_hugepage_test.c             | 25 +++++++++++++++++
 3 files changed, 43 insertions(+), 10 deletions(-)

--
2.39.2.637.g21b0678d19-goog