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Andrea Arcangeli 5025ad140e BACKPORT: userfaultfd: UFFDIO_MOVE uABI 
Implement the uABI of UFFDIO_MOVE ioctl.
UFFDIO_COPY performs ~20% better than UFFDIO_MOVE when the application
needs pages to be allocated [1]. However, with UFFDIO_MOVE, if pages are
available (in userspace) for recycling, as is usually the case in heap
compaction algorithms, then we can avoid the page allocation and memcpy
(done by UFFDIO_COPY). Also, since the pages are recycled in the
userspace, we avoid the need to release (via madvise) the pages back to
the kernel [2].

We see over 40% reduction (on a Google pixel 6 device) in the compacting
thread's completion time by using UFFDIO_MOVE vs.  UFFDIO_COPY.  This was
measured using a benchmark that emulates a heap compaction implementation
using userfaultfd (to allow concurrent accesses by application threads).
More details of the usecase are explained in [2].  Furthermore,
UFFDIO_MOVE enables moving swapped-out pages without touching them within
the same vma.  Today, it can only be done by mremap, however it forces
splitting the vma.

[1] https://lore.kernel.org/all/1425575884-2574-1-git-send-email-aarcange@redhat.com/
[2] https://lore.kernel.org/linux-mm/CA+EESO4uO84SSnBhArH4HvLNhaUQ5nZKNKXqxRCyjniNVjp0Aw@mail.gmail.com/

Update for the ioctl_userfaultfd(2)  manpage:

   UFFDIO_MOVE
       (Since Linux xxx)  Move a continuous memory chunk into the
       userfault registered range and optionally wake up the blocked
       thread. The source and destination addresses and the number of
       bytes to move are specified by the src, dst, and len fields of
       the uffdio_move structure pointed to by argp:

           struct uffdio_move {
               __u64 dst;    /* Destination of move */
               __u64 src;    /* Source of move */
               __u64 len;    /* Number of bytes to move */
               __u64 mode;   /* Flags controlling behavior of move */
               __s64 move;   /* Number of bytes moved, or negated error */
           };

       The following value may be bitwise ORed in mode to change the
       behavior of the UFFDIO_MOVE operation:

       UFFDIO_MOVE_MODE_DONTWAKE
              Do not wake up the thread that waits for page-fault
              resolution

       UFFDIO_MOVE_MODE_ALLOW_SRC_HOLES
              Allow holes in the source virtual range that is being moved.
              When not specified, the holes will result in ENOENT error.
              When specified, the holes will be accounted as successfully
              moved memory. This is mostly useful to move hugepage aligned
              virtual regions without knowing if there are transparent
              hugepages in the regions or not, but preventing the risk of
              having to split the hugepage during the operation.

       The move field is used by the kernel to return the number of
       bytes that was actually moved, or an error (a negated errno-
       style value).  If the value returned in move doesn't match the
       value that was specified in len, the operation fails with the
       error EAGAIN.  The move field is output-only; it is not read by
       the UFFDIO_MOVE operation.

       The operation may fail for various reasons. Usually, remapping of
       pages that are not exclusive to the given process fail; once KSM
       might deduplicate pages or fork() COW-shares pages during fork()
       with child processes, they are no longer exclusive. Further, the
       kernel might only perform lightweight checks for detecting whether
       the pages are exclusive, and return -EBUSY in case that check fails.
       To make the operation more likely to succeed, KSM should be
       disabled, fork() should be avoided or MADV_DONTFORK should be
       configured for the source VMA before fork().

       This ioctl(2) operation returns 0 on success.  In this case, the
       entire area was moved.  On error, -1 is returned and errno is
       set to indicate the error.  Possible errors include:

       EAGAIN The number of bytes moved (i.e., the value returned in
              the move field) does not equal the value that was
              specified in the len field.

       EINVAL Either dst or len was not a multiple of the system page
              size, or the range specified by src and len or dst and len
              was invalid.

       EINVAL An invalid bit was specified in the mode field.

       ENOENT
              The source virtual memory range has unmapped holes and
              UFFDIO_MOVE_MODE_ALLOW_SRC_HOLES is not set.

       EEXIST
              The destination virtual memory range is fully or partially
              mapped.

       EBUSY
              The pages in the source virtual memory range are either
              pinned or not exclusive to the process. The kernel might
              only perform lightweight checks for detecting whether the
              pages are exclusive. To make the operation more likely to
              succeed, KSM should be disabled, fork() should be avoided
              or MADV_DONTFORK should be configured for the source virtual
              memory area before fork().

       ENOMEM Allocating memory needed for the operation failed.

       ESRCH
              The target process has exited at the time of a UFFDIO_MOVE
              operation.

Link: https://lkml.kernel.org/r/20231206103702.3873743-3-surenb@google.com
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Brian Geffon <bgeffon@google.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jann Horn <jannh@google.com>
Cc: Kalesh Singh <kaleshsingh@google.com>
Cc: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Lokesh Gidra <lokeshgidra@google.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport (IBM) <rppt@kernel.org>
Cc: Nicolas Geoffray <ngeoffray@google.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: ZhangPeng <zhangpeng362@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

(cherry picked from commit adef440691bab824e39c1b17382322d195e1fab0)
Conflicts:
        mm/huge_memory.c
        mm/userfaultfd.c

1. Add vma parameter in mmu_notifier_range_init() calls.
2. Replace folio_move_anon_rmap() with page_move_anon_rmap().
3. Remove vma parameter in pmd_mkwrite() calls.
4. Replace pte_offset_map_nolock() with pte_offset_map()+pte_lockptr()
combo.
5. Remove VM_SHADOW_STACK in vma_move_compatible().
6. Replace pmdp_get_lockless() with pmd_read_atomic().

Bug: 274911254
Change-Id: I1116f15a395f1a8bac176906f7f9c2411e59dc54
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Lokesh Gidra <lokeshgidra@google.com>
2024-04-22 18:09:14 +00:00
android ANDROID: abi_gki_aarch64_qcom: Update symbol list 2024-04-22 11:04:47 +05:30
arch ANDROID: gki_defconfig: Sync gki_defconfig 2024-04-22 11:02:55 +05:30
block Reapply "ANDROID: block: Add support for filesystem requests and small segments" 2024-04-17 18:38:54 +00:00
certs This is the 6.1.11 stable release 2023-02-09 13:29:55 +00:00
crypto Reapply "Merge tag 'android14-6.1.75_r00' into android14-6.1" 2024-04-02 19:49:12 +00:00
Documentation BACKPORT: userfaultfd: UFFDIO_MOVE uABI 2024-04-22 18:09:14 +00:00
drivers ANDROID: vendor_hooks: Add hooks to support hibernation 2024-04-22 11:04:11 +05:30
fs BACKPORT: userfaultfd: UFFDIO_MOVE uABI 2024-04-22 18:09:14 +00:00
include BACKPORT: userfaultfd: UFFDIO_MOVE uABI 2024-04-22 18:09:14 +00:00
init Reapply "Merge tag 'android14-6.1.75_r00' into android14-6.1" 2024-04-02 19:49:12 +00:00
io_uring Reapply "Merge tag 'android14-6.1.75_r00' into android14-6.1" 2024-04-02 19:49:12 +00:00
ipc ipc: fix memory leak in init_mqueue_fs() 2022-12-31 13:32:01 +01:00
kernel ANDROID: PM: hibernate: Encryption support with compression 2024-04-22 11:05:17 +05:30
lib Reapply "Merge tag 'android14-6.1.75_r00' into android14-6.1" 2024-04-02 19:49:12 +00:00
LICENSES LICENSES/LGPL-2.1: Add LGPL-2.1-or-later as valid identifiers 2021-12-16 14:33:10 +01:00
mm BACKPORT: userfaultfd: UFFDIO_MOVE uABI 2024-04-22 18:09:14 +00:00
net UPSTREAM: netfilter: nf_tables: release mutex after nft_gc_seq_end from abort path 2024-04-15 11:20:28 +00:00
rust rust: allocator: Prevent mis-aligned allocation 2023-08-11 12:08:18 +02:00
samples Merge 6.1.60 into android14-6.1-lts 2023-11-03 16:23:47 +00:00
scripts Reapply "Merge tag 'android14-6.1.75_r00' into android14-6.1" 2024-04-02 19:49:12 +00:00
security Reapply "Merge tag 'android14-6.1.75_r00' into android14-6.1" 2024-04-02 19:49:12 +00:00
sound UPSTREAM: ALSA: virtio: Fix "Coverity: virtsnd_kctl_tlv_op(): Uninitialized variables" warning. 2024-04-04 15:35:58 +00:00
tools Reapply "Merge tag 'android14-6.1.75_r00' into android14-6.1" 2024-04-02 19:49:12 +00:00
usr usr/gen_init_cpio.c: remove unnecessary -1 values from int file 2022-10-03 14:21:44 -07:00
virt kvm/vfio: ensure kvg instance stays around in kvm_vfio_group_add() 2023-09-13 09:42:46 +02:00
.clang-format inet: ping: use hlist_nulls rcu iterator during lookup 2022-12-01 12:42:46 +01:00
.cocciconfig
.get_maintainer.ignore get_maintainer: add Alan to .get_maintainer.ignore 2022-08-20 15:17:44 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore ANDROID: add Android KABI build files to root .gitignore file 2023-06-09 13:12:00 +00:00
.mailmap 9 hotfixes. 6 for MM, 3 for other areas. Four of these patches address 2022-12-10 17:10:52 -08:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
BUILD.bazel ANDROID: Add known structs used by modules to KMI 2024-04-16 13:49:35 -07:00
build.config.aarch64 ANDROID: Move NDK_TRIPLE to build.config.constants. 2023-02-14 14:13:51 -08:00
build.config.allmodconfig ANDROID: Revert "ANDROID: allmodconfig: disable WERROR" 2023-08-21 17:29:29 +01:00
build.config.allmodconfig.aarch64 ANDROID: drop KERNEL_DIR setting in build.config.common 2020-08-31 15:20:37 +00:00
build.config.allmodconfig.arm ANDROID: drop KERNEL_DIR setting in build.config.common 2020-08-31 15:20:37 +00:00
build.config.allmodconfig.x86_64 ANDROID: drop KERNEL_DIR setting in build.config.common 2020-08-31 15:20:37 +00:00
build.config.amlogic ANDROID: Unnest MAKE_GOALS from build configs 2023-05-02 13:37:21 +00:00
build.config.arm ANDROID: kleaf: move NDK_TRIPLE for arm to build.config.constants. 2023-05-09 22:36:11 +00:00
build.config.common ANDROID: 6/16/2023 KMI update 2023-06-16 20:49:51 +00:00
build.config.constants ANDROID: clang: update to 17.0.2 2023-05-15 18:53:36 +00:00
build.config.crashdump ANDROID: Move microdroid and crashdump defconfigs to common 2023-09-27 15:30:26 +00:00
build.config.crashdump.aarch64 ANDROID: Move microdroid and crashdump defconfigs to common 2023-09-27 15:30:26 +00:00
build.config.crashdump.x86_64 ANDROID: Move microdroid and crashdump defconfigs to common 2023-09-27 15:30:26 +00:00
build.config.db845c Reapply "Merge tag 'android14-6.1.75_r00' into android14-6.1" 2024-04-02 19:49:12 +00:00
build.config.gki ANDROID: GKI: Source GKI_BUILD_CONFIG_FRAGMENT after setting all variables 2022-12-27 13:52:08 -08:00
build.config.gki_kasan ANDROID: build.config: re-disable LTO properly for KASAN 2022-03-24 12:41:35 -07:00
build.config.gki_kasan.aarch64 ANDROID: drop KERNEL_DIR setting in build.config.common 2020-08-31 15:20:37 +00:00
build.config.gki_kasan.x86_64 ANDROID: drop KERNEL_DIR setting in build.config.common 2020-08-31 15:20:37 +00:00
build.config.gki_kprobes ANDROID: build.configs: migrate away from CC_LD_ARG 2021-07-02 09:49:23 +00:00
build.config.gki_kprobes.aarch64 ANDROID: Adding kprobes build configs for Cuttlefish 2021-03-01 15:29:45 +00:00
build.config.gki_kprobes.x86_64 ANDROID: Adding kprobes build configs for Cuttlefish 2021-03-01 15:29:45 +00:00
build.config.gki-debug.aarch64 ANDROID: drop KERNEL_DIR setting in build.config.common 2020-08-31 15:20:37 +00:00
build.config.gki-debug.x86_64 ANDROID: drop KERNEL_DIR setting in build.config.common 2020-08-31 15:20:37 +00:00
build.config.gki.aarch64 ANDROID: Delete MODULES_LIST from build configs. 2023-06-21 11:18:02 +00:00
build.config.gki.aarch64.fips140 ANDROID: remove LTO check from build.config.gki.aarch64.fips140 2024-03-04 11:19:25 +00:00
build.config.gki.riscv64 ANDROID: Delete MODULES_LIST from build configs. 2023-06-21 11:18:02 +00:00
build.config.gki.x86_64 ANDROID: Delete MODULES_LIST from build configs. 2023-06-21 11:18:02 +00:00
build.config.khwasan ANDROID: Add a build config fragment for KHWASan. 2021-10-13 19:44:44 +00:00
build.config.microdroid ANDROID: Move microdroid and crashdump defconfigs to common 2023-09-27 15:30:26 +00:00
build.config.microdroid.aarch64 ANDROID: Move microdroid and crashdump defconfigs to common 2023-09-27 15:30:26 +00:00
build.config.microdroid.x86_64 ANDROID: Move microdroid and crashdump defconfigs to common 2023-09-27 15:30:26 +00:00
build.config.riscv64 ANDROID: GKI: Add 64-bit RISC-V config 2022-12-08 20:01:15 +00:00
build.config.rockchip ANDROID: GKI: Add rockchip fragment and build.config 2023-09-19 17:36:15 +00:00
build.config.rockpi4 ANDROID: db845c: Remove MAKE_GOALS from build.config 2023-05-15 07:01:39 +00:00
build.config.x86_64 ANDROID: Move NDK_TRIPLE to build.config.constants. 2023-02-14 14:13:51 -08:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: Remove Michal Marek from Kbuild maintainers 2022-11-16 14:53:00 +09:00
Kbuild Kbuild updates for v6.1 2022-10-10 12:00:45 -07:00
Kconfig ANDROID: kbuild: add Kconfig support for external modules 2021-12-13 18:33:18 +00:00
Kconfig.ext ANDROID: kbuild: add Kconfig support for external modules 2021-12-13 18:33:18 +00:00
MAINTAINERS Reapply "Merge tag 'android14-6.1.75_r00' into android14-6.1" 2024-04-02 19:49:12 +00:00
Makefile Reapply "Merge tag 'android14-6.1.75_r00' into android14-6.1" 2024-04-02 19:49:12 +00:00
modules.bzl Revert "ANDROID: Build null_blk and scsi_debug as kernel modules" 2024-02-29 10:22:01 -08:00
OWNERS ANDROID: Enable GKI Dr. No Enforcement 2023-06-15 09:54:33 +01:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00
README.md ANDROID: README.md: fix checkpatch.pl path typo 2021-04-07 23:16:50 +00:00

README.md

How do I submit patches to Android Common Kernels

  1. BEST: Make all of your changes to upstream Linux. If appropriate, backport to the stable releases. These patches will be merged automatically in the corresponding common kernels. If the patch is already in upstream Linux, post a backport of the patch that conforms to the patch requirements below.

    • Do not send patches upstream that contain only symbol exports. To be considered for upstream Linux, additions of EXPORT_SYMBOL_GPL() require an in-tree modular driver that uses the symbol -- so include the new driver or changes to an existing driver in the same patchset as the export.
    • When sending patches upstream, the commit message must contain a clear case for why the patch is needed and beneficial to the community. Enabling out-of-tree drivers or functionality is not not a persuasive case.

  2. LESS GOOD: Develop your patches out-of-tree (from an upstream Linux point-of-view). Unless these are fixing an Android-specific bug, these are very unlikely to be accepted unless they have been coordinated with kernel-team@android.com. If you want to proceed, post a patch that conforms to the patch requirements below.

Common Kernel patch requirements

  • All patches must conform to the Linux kernel coding standards and pass scripts/checkpatch.pl
  • Patches shall not break gki_defconfig or allmodconfig builds for arm, arm64, x86, x86_64 architectures (see https://source.android.com/setup/build/building-kernels)
  • If the patch is not merged from an upstream branch, the subject must be tagged with the type of patch: UPSTREAM:, BACKPORT:, FROMGIT:, FROMLIST:, or ANDROID:.
  • All patches must have a Change-Id: tag (see https://gerrit-review.googlesource.com/Documentation/user-changeid.html)
  • If an Android bug has been assigned, there must be a Bug: tag.
  • All patches must have a Signed-off-by: tag by the author and the submitter

Additional requirements are listed below based on patch type

Requirements for backports from mainline Linux: UPSTREAM:, BACKPORT:

  • If the patch is a cherry-pick from Linux mainline with no changes at all
    • tag the patch subject with UPSTREAM:.
    • add upstream commit information with a (cherry picked from commit ...) line
    • Example:
      • if the upstream commit message is
        important patch from upstream

        This is the detailed description of the important patch

        Signed-off-by: Fred Jones <fred.jones@foo.org>
  • then Joe Smith would upload the patch for the common kernel as
        UPSTREAM: important patch from upstream

        This is the detailed description of the important patch

        Signed-off-by: Fred Jones <fred.jones@foo.org>

        Bug: 135791357
        Change-Id: I4caaaa566ea080fa148c5e768bb1a0b6f7201c01
        (cherry picked from commit c31e73121f4c1ec41143423ac6ce3ce6dafdcec1)
        Signed-off-by: Joe Smith <joe.smith@foo.org>
  • If the patch requires any changes from the upstream version, tag the patch with BACKPORT: instead of UPSTREAM:.
    • use the same tags as UPSTREAM:
    • add comments about the changes under the (cherry picked from commit ...) line
    • Example:
        BACKPORT: important patch from upstream

        This is the detailed description of the important patch

        Signed-off-by: Fred Jones <fred.jones@foo.org>

        Bug: 135791357
        Change-Id: I4caaaa566ea080fa148c5e768bb1a0b6f7201c01
        (cherry picked from commit c31e73121f4c1ec41143423ac6ce3ce6dafdcec1)
        [joe: Resolved minor conflict in drivers/foo/bar.c ]
        Signed-off-by: Joe Smith <joe.smith@foo.org>

Requirements for other backports: FROMGIT:, FROMLIST:,

  • If the patch has been merged into an upstream maintainer tree, but has not yet been merged into Linux mainline
    • tag the patch subject with FROMGIT:
    • add info on where the patch came from as (cherry picked from commit <sha1> <repo> <branch>). This must be a stable maintainer branch (not rebased, so don't use linux-next for example).
    • if changes were required, use BACKPORT: FROMGIT:
    • Example:
      • if the commit message in the maintainer tree is
        important patch from upstream

        This is the detailed description of the important patch

        Signed-off-by: Fred Jones <fred.jones@foo.org>
  • then Joe Smith would upload the patch for the common kernel as
        FROMGIT: important patch from upstream

        This is the detailed description of the important patch

        Signed-off-by: Fred Jones <fred.jones@foo.org>

        Bug: 135791357
        (cherry picked from commit 878a2fd9de10b03d11d2f622250285c7e63deace
         https://git.kernel.org/pub/scm/linux/kernel/git/foo/bar.git test-branch)
        Change-Id: I4caaaa566ea080fa148c5e768bb1a0b6f7201c01
        Signed-off-by: Joe Smith <joe.smith@foo.org>
  • If the patch has been submitted to LKML, but not accepted into any maintainer tree
    • tag the patch subject with FROMLIST:
    • add a Link: tag with a link to the submittal on lore.kernel.org
    • add a Bug: tag with the Android bug (required for patches not accepted into a maintainer tree)
    • if changes were required, use BACKPORT: FROMLIST:
    • Example:
        FROMLIST: important patch from upstream

        This is the detailed description of the important patch

        Signed-off-by: Fred Jones <fred.jones@foo.org>

        Bug: 135791357
        Link: https://lore.kernel.org/lkml/20190619171517.GA17557@someone.com/
        Change-Id: I4caaaa566ea080fa148c5e768bb1a0b6f7201c01
        Signed-off-by: Joe Smith <joe.smith@foo.org>

Requirements for Android-specific patches: ANDROID:

  • If the patch is fixing a bug to Android-specific code
    • tag the patch subject with ANDROID:
    • add a Fixes: tag that cites the patch with the bug
    • Example:
        ANDROID: fix android-specific bug in foobar.c

        This is the detailed description of the important fix

        Fixes: 1234abcd2468 ("foobar: add cool feature")
        Change-Id: I4caaaa566ea080fa148c5e768bb1a0b6f7201c01
        Signed-off-by: Joe Smith <joe.smith@foo.org>
  • If the patch is a new feature
    • tag the patch subject with ANDROID:
    • add a Bug: tag with the Android bug (required for android-specific features)