commit 62f3d531e41a7e6e0dc8d37ea377c50488decb56 upstream.

scx_bpf_dsq_reenq() is registered with KF_IMPLICIT_ARGS and its kernel BTF
prototype omits the trailing bpf_prog_aux argument. The ___compat extern
declares the argument explicitly, so libbpf never matches the prototype and
the weak extern silently stays unresolved on every kernel. The wrapper
always takes the old fallback path, which disables generic reenq users like
scx_qmap's lowpri mechanism and fails non-local reenq with "kernel too old"
even on kernels that have the kfunc.

Drop the explicit aux argument. Also correct the stale v6.20 reference, the
kfunc was added in v7.1.

Fixes: 9c34c5074d1b ("sched_ext: Introduce scx_bpf_dsq_reenq() for remote local DSQ reenqueue")
Cc: stable@vger.kernel.org # v7.1+
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

commit f7b6d128dd49a6eec09066ecfd29095f12588786 upstream.

scx_prio_less() implements prio_less() semantics - %true means that @a is
the lower priority and should run after @b. ops.core_sched_before() is
documented to return %true when @a should run before @b. scx_prio_less()
returns the op's value as-is, inverting the documented semantics at runtime.

Call the op with the arguments swapped.

scx_qmap followed the wiring instead of the documentation and returned %true
for the younger task, so the two inversions canceled out and it behaved as
intended. Flip its comparison to match. scx_qmap is likely the only current
user in or out of the kernel tree. Any scheduler written the same way needs
the same flip, while schedulers following the documentation are fixed by
this change.

Fixes: 7b0888b7cc19 ("sched_ext: Implement core-sched support")
Cc: stable@vger.kernel.org # v6.12+
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

commit 56bbc91219c0711f1580a8ba7cd60471b6e1684e upstream.

libbpf strips the last ___flavor suffix when resolving kfunc externs, so
the bare ___v2 declaration resolves to scx_bpf_dsq_move_to_local, whose
BTF proto lacks @enq_flags. The extern never matches, bpf_ksym_exists()
returns false on every kernel that has the ___v2 kfunc, and the macro
falls back to ___v1, silently dropping @enq_flags.

Add the trailing ___compat suffix used by the other versioned externs in
this file (scx_bpf_dsq_insert___v2, scx_bpf_reenqueue_local___v2).

Any caller passing non-zero @enq_flags through the compat macro silently
loses them.

Fixes: 860683763ebf ("sched_ext: Add enq_flags to scx_bpf_dsq_move_to_local()")
Cc: stable@vger.kernel.org # v7.1+
Assisted-by: Z.ai:glm-5.2
Signed-off-by: fangqiurong <fangqiurong@kylinos.cn>
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

commit ffaab58d217581cb75353168f8812a16e10463fc upstream.

SCX_RQ_BAL_KEEP tells the pick to keep running the previous task, a leftover
from when balancing and picking were separate operations. An rq-level flag
only works while dispatches and picks pair up one to one, which core
scheduling breaks: selections interleave through dispatch's lock drops and a
pick can consume a stale flag, keeping a task that has since been dequeued.
Fixing core scheduling support requires the decision to travel with the
dispatch that made it. Make scx_dispatch_sched() and balance_one() return an
explicit verdict instead and drop the flag's plumbing from the tools autogen
enum headers.

Also factor the pick-side invocation, its follow-up queueing and the
post-dispatch checks out of do_pick_task_scx() into dispatch_pick(). No
functional changes intended.

v2: Drop the SCX_RQ_BAL_KEEP plumbing from the tools autogen enum headers
    as well (Andrea).

Fixes: 4c95380701f5 ("sched/ext: Fold balance_scx() into pick_task_scx()")
Cc: stable@vger.kernel.org # v6.19+
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

cmask_equal(), cmask_weight() and cmask_subset() bounded their word walks
with CMASK_NR_WORDS(nr_cids), which pads by one word and can't tell the last
word in use without @base. The walks could thus cover a slack word past the
active range, which cmask_reframe() leaves non-zero: a stale bit there gave
cmask_equal() a spurious mismatch, cmask_weight() an inflated count, and
cmask_subset() a spurious violation. cmask_subset() could also read
@b->bits[] one word past its allocation (within the arena's fault-recovered
range, so harmless), and deviated from the kernel scx_cmask_subset() by
failing any @a range that doesn't nest inside @b's even when the overhanging
bits are all clear.

Bound the cmask_equal() and cmask_weight() walks by the words the range
actually spans, with early returns for empty ranges. Rewrite cmask_subset()
to match the kernel semantics: scan @a's overhangs for set bits with
cmask_next_set() and walk the words of the range intersection.
cmask_subset() moves below cmask_next_set(), which it now uses. Padding bits
don't need masking as every cmask helper keeps them clear.

Fixes: a58e6b79b432 ("sched_ext: Add cmask, a base-windowed bitmap over cid space")
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Andrea Righi <arighi@nvidia.com>

The sched_ext sources had grown to ten ext* files directly under
kernel/sched/. Move them into a new kernel/sched/ext/ subdirectory and drop
the now-redundant ext_ prefix. ext.c/h keep their names.

  kernel/sched/ext.{c,h}       -> kernel/sched/ext/ext.{c,h}
  kernel/sched/ext_internal.h  -> kernel/sched/ext/internal.h
  kernel/sched/ext_types.h     -> kernel/sched/ext/types.h
  kernel/sched/ext_idle.{c,h}  -> kernel/sched/ext/idle.{c,h}
  kernel/sched/ext_cid.{c,h}   -> kernel/sched/ext/cid.{c,h}
  kernel/sched/ext_arena.{c,h} -> kernel/sched/ext/arena.{c,h}

The include paths in build_policy.c and sched.h, the MAINTAINERS glob, and a
few documentation and comment references are updated to match. No code or
symbol changes.

Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Reviewed-by: Andrea Righi <arighi@nvidia.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

Pull sched_ext updates from Tejun Heo:
 "Most of this continues the in-development sub-scheduler support, which
  lets a root BPF scheduler delegate to nested sub-schedulers. The
  dispatch-path building blocks landed in 7.1. A follow-up patchset in
  development will complete enqueue-path support for hierarchical
  scheduling. This cycle adds most of that infrastructure:

   - Topological CPU IDs (cids): a dense, topology-ordered CPU numbering
     where the CPUs of a core, LLC, or NUMA node form contiguous ranges,
     so a topology unit becomes a (start, length) slice. Raw CPU numbers
     are sparse and don't track topological closeness, which makes them
     clumsy for sharding work across sub-schedulers and awkward in BPF.

   - cmask: bitmaps windowed over a slice of cid space, so a
     sub-scheduler can track, for example, the idle cids of its shard
     without a full NR_CPUS cpumask.

   - A struct_ops variant that cid-form sub-schedulers register with,
     along with the cid-form kfuncs they call.

   - BPF arena integration, which sub-scheduler support is built on. The
     bpf-next additions let the kernel read and write the BPF
     scheduler's arena directly, turning it into a real kernel/BPF
     shared-memory channel. Shared state like the per-CPU cmask now
     lives there.

   - scx_qmap is reworked to exercise the new arena and cid interfaces.

  Additionally:

   - Exit-dump improvements: dump the faulting CPU first, expose the
     exit CPU to BPF and userspace, and normalize the dump header.

   - Misc kfuncs and cleanups: a task-ID lookup kfunc, __printf checking
     on the error and dump formatters, header reorganization, and
     assorted fixes"

* tag 'sched_ext-for-7.2' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/sched_ext: (59 commits)
  sched_ext: Add scx_arena_to_kaddr() / scx_kaddr_to_arena()
  sched_ext: Make scx_bpf_kick_cid() return s32
  sched_ext: Add scx_cmask_test() and scx_cmask_for_each_cid()
  tools/sched_ext: Order single-cid cmask helpers as (cid, mask)
  sched_ext: Order single-cid cmask helpers as (cid, mask)
  selftests/sched_ext: Fix dsq_move_to_local check
  sched_ext: Guard BPF arena helper calls to fix 32-bit build
  sched_ext: idle: Fix errno loss in scx_idle_init()
  sched_ext: Convert ops.set_cmask() to arena-resident cmask
  sched_ext: Sub-allocator over kernel-claimed BPF arena pages
  sched_ext: Require an arena for cid-form schedulers
  sched_ext: Add cmask mask ops
  sched_ext: Track bits[] storage size in struct scx_cmask
  sched_ext: Rename scx_cmask.nr_bits to nr_cids
  tools/sched_ext: scx_qmap: Fix qa arena placement
  sched_ext: Mark !CONFIG_EXT_SUB_SCHED dummy stubs static inline
  sched_ext: Replace tryget_task_struct() with get_task_struct()
  sched_ext: Add scx_task_iter_relock() and use it in scx_root_enable_workfn()
  sched_ext: Fix ops_cid layout assert
  sched_ext: Use offsetofend on both sides of the ops_cid layout assert
  ...

Switch scx_bpf_kick_cid() from void to s32 so future cap enforcement can
surface failures. cid interface is introduced in this cycle and has no
external users, so the ABI change is safe. Subsequent patches will add
-EPERM returns when the calling sub-sched lacks the required cap on the
target cid.

v2: Return scx_cid_to_cpu()'s errno instead of -EINVAL. (Andrea)

Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Andrea Righi <arighi@nvidia.com>

The BPF arena single-cid cmask helpers take the cmask first and the cid
second. Reorder them to (cid, mask) to match the kernel-side helpers and
the test_bit(nr, addr), cpumask_test_cpu(cpu, mask) convention. Range and
iteration helpers keep (mask, start).

Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Andrea Righi <arighi@nvidia.com>

scx_show_state.py still reads scx_aborting and scx_bypass_depth as
global symbols. Those symbols no longer exist after the state was moved
into struct scx_sched, so the drgn script fails when it reaches either
field.

Read aborting and bypass_depth from scx_root instead. This preserves the
script's current root-scheduler view: with sub-scheduler support, the
reported values are for the root scheduler and sub-schedulers are not
enumerated.

Fixes: 5c8d98a1b4de ("sched_ext: Move bypass state into scx_sched")
Fixes: c1743da43cf5 ("sched_ext: Move aborting flag to per-scheduler field")
Signed-off-by: Zicheng Qu <quzicheng@huawei.com>
Reviewed-by: Andrea Righi <arighi@nvidia.com>
Signed-off-by: Tejun Heo <tj@kernel.org>