Date:   Tue, 21 Mar 2023 20:15:31 +0000
Mime-Version: 1.0
Message-ID: <cover.1679428901.git.ackerleytng@google.com>
Subject: [RFC PATCH v2 0/2] Providing mount in memfd_restricted() syscall
From:   Ackerley Tng <ackerleytng@google.com>
To:     kvm@vger.kernel.org, linux-api@vger.kernel.org,
        linux-arch@vger.kernel.org, linux-doc@vger.kernel.org,
        linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-mm@kvack.org, qemu-devel@nongnu.org
Cc:     aarcange@redhat.com, ak@linux.intel.com, akpm@linux-foundation.org,
        arnd@arndb.de, bfields@fieldses.org, bp@alien8.de,
        chao.p.peng@linux.intel.com, corbet@lwn.net, dave.hansen@intel.com,
        david@redhat.com, ddutile@redhat.com, dhildenb@redhat.com,
        hpa@zytor.com, hughd@google.com, jlayton@kernel.org,
        jmattson@google.com, joro@8bytes.org, jun.nakajima@intel.com,
        kirill.shutemov@linux.intel.com, linmiaohe@huawei.com,
        luto@kernel.org, mail@maciej.szmigiero.name, mhocko@suse.com,
        michael.roth@amd.com, mingo@redhat.com, naoya.horiguchi@nec.com,
        pbonzini@redhat.com, qperret@google.com, rppt@kernel.org,
        seanjc@google.com, shuah@kernel.org, steven.price@arm.com,
        tabba@google.com, tglx@linutronix.de, vannapurve@google.com,
        vbabka@suse.cz, vkuznets@redhat.com, wanpengli@tencent.com,
        wei.w.wang@intel.com, x86@kernel.org, yu.c.zhang@linux.intel.com,
        Ackerley Tng <ackerleytng@google.com>
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Hello,

This patchset builds upon the memfd_restricted() system call that was
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@linux.int=
el.com/T/#m7e944d7892afdd1d62a03a287bd488c56e377b0c

The tree can be found at:
https://github.com/googleprodkernel/linux-cc/tree/restrictedmem-provide-mou=
nt-fd

In this patchset, a modification to the memfd_restricted() syscall is
proposed, which allows userspace to provide a mount, on which the
restrictedmem file will be created and returned from the
memfd_restricted().

Allowing userspace to provide a mount allows userspace to control
various memory binding policies via tmpfs mount options, such as
Transparent HugePage memory allocation policy through
'huge=3Dalways/never' and NUMA memory allocation policy through
'mpol=3Dlocal/bind:*'.

Changes since RFCv1:
+ Use fd to represent mount instead of path string, as Kirill
  suggested. I believe using fds makes this syscall interface more
  aligned with the other syscalls like fsopen(), fsconfig(), and
  fsmount() in terms of using and passing around fds
+ Remove unused variable char *orig_shmem_enabled from selftests

Dependencies:
+ Sean's iteration of the =E2=80=98KVM: mm: fd-based approach for supportin=
g
  KVM=E2=80=99 patch series at
  https://github.com/sean-jc/linux/tree/x86/upm_base_support
+ Proposed fixes for these issues mentioned on the mailing list:
    + https://lore.kernel.org/lkml/diqzzga0fv96.fsf@ackerleytng-cloudtop-sg=
.c.googlers.com/

Links to earlier patch series:
+ RFC v1:
  https://lore.kernel.org/lkml/cover.1676507663.git.ackerleytng@google.com/=
T/

Ackerley Tng (2):
  mm: restrictedmem: Allow userspace to specify mount for
    memfd_restricted
  selftests: restrictedmem: Check hugepage-ness of shmem file backing
    restrictedmem fd

 include/linux/syscalls.h                      |   2 +-
 include/uapi/linux/restrictedmem.h            |   8 +
 mm/restrictedmem.c                            |  63 ++-
 tools/testing/selftests/Makefile              |   1 +
 .../selftests/restrictedmem/.gitignore        |   3 +
 .../testing/selftests/restrictedmem/Makefile  |  15 +
 .../testing/selftests/restrictedmem/common.c  |   9 +
 .../testing/selftests/restrictedmem/common.h  |   8 +
 .../restrictedmem_hugepage_test.c             | 459 ++++++++++++++++++
 9 files changed, 561 insertions(+), 7 deletions(-)
 create mode 100644 include/uapi/linux/restrictedmem.h
 create mode 100644 tools/testing/selftests/restrictedmem/.gitignore
 create mode 100644 tools/testing/selftests/restrictedmem/Makefile
 create mode 100644 tools/testing/selftests/restrictedmem/common.c
 create mode 100644 tools/testing/selftests/restrictedmem/common.h
 create mode 100644 tools/testing/selftests/restrictedmem/restrictedmem_hug=
epage_test.c

--
2.40.0.rc2.332.ga46443480c-goog