linux-kernel - [RFC PATCH bpf-next 0/8] bpf, sched_ext: Make kfunc filters support struct

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Message-ID:
 <AM6PR03MB5080261D024B49D26F3FFF0099F72@AM6PR03MB5080.eurprd03.prod.outlook.com>
Date: Wed,  5 Feb 2025 19:27:09 +0000
From: Juntong Deng <juntong.deng@...look.com>
To: ast@...nel.org,
	daniel@...earbox.net,
	john.fastabend@...il.com,
	andrii@...nel.org,
	martin.lau@...ux.dev,
	eddyz87@...il.com,
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Cc: bpf@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [RFC PATCH bpf-next 0/8] bpf, sched_ext: Make kfunc filters support struct_ops context to reduce runtime overhead

This patch series makes kfunc filters support the use of struct_ops
context information and adds corresponding filters for various kfunc
sets in SCX.

After improving kfunc filters, SCX no longer needs the mask-based
runtime kfuncs call restriction, so this patch removes the mask-based
runtime restriction and updates the corresponding test case.

I added *st_ops as part of the context information to avoid kfuncs being
incorrectly blocked when used in non-SCX scenarios where the member
offsets would have a different meaning (not sure if this is necessary).

Note that this is an RFC patch series and I am not sure if I
misunderstood something or broke something.

If I got something wrong please let me know.

Known issues:

scx_bpf_dsq_move appears in both scx_kfunc_ids_dispatch and
scx_kfunc_ids_unlocked.

This results in scx_bpf_dsq_move being incorrectly blocked by
the filter of scx_kfunc_ids_dispatch in the 'init' context.

The scx_qmap sample program fails because of this.

In the filter-based restrictions, each kfunc can only appear in
one kfunc set.

A possible solution is to add a scx_kfunc_set_unlocked_dispatch
kfunc set.

Signed-off-by: Juntong Deng <juntong.deng@...look.com>

Juntong Deng (8):
  bpf: Add struct_ops context information to struct bpf_prog_aux
  sched_ext: Add filter for scx_kfunc_ids_select_cpu
  sched_ext: Add filter for scx_kfunc_ids_enqueue_dispatch
  sched_ext: Add filter for scx_kfunc_ids_dispatch
  sched_ext: Add filter for scx_kfunc_ids_cpu_release
  sched_ext: Add filter for scx_kfunc_ids_unlocked
  sched_ext: Removed mask-based runtime restrictions on calling kfuncs
    in different contexts
  selftests/sched_ext: Update enq_select_cpu_fails to adapt to
    struct_ops context filter

 include/linux/bpf.h                           |   2 +
 include/linux/sched/ext.h                     |  24 --
 kernel/bpf/verifier.c                         |   8 +-
 kernel/sched/ext.c                            | 354 +++++++++---------
 .../sched_ext/enq_select_cpu_fails.c          |  35 +-
 5 files changed, 184 insertions(+), 239 deletions(-)

-- 
2.39.5