sched_ext: Convert ops.set_cmask() to arena-resident cmask

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ops_cid.set_cmask() expects a cmask. The kernel couldn't write into the
arena, so it translated cpumask -> cmask in kernel memory and passed the
result as a trusted pointer. The BPF cmask helpers all operate on arena
cmasks though, so the BPF side had to word-by-word probe-read the kernel
cmask into an arena cmask via cmask_copy_from_kernel() before any helper
could touch it. It works, but is clumsy.

With direct kernel-side arena access now in place, build the cmask in the
arena. The kernel writes to it through the kern_va side of the dual mapping.
BPF directly dereferences it via an __arena pointer like any other arena
struct.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Emil Tsalapatis <emil@etsalapatis.com>

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This commit is contained in:

Tejun Heo 2026-05-22 07:06:01 -10:00

parent 9eca087deb

commit abdc2516f1

5 changed files with 75 additions and 80 deletions

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68

kernel/sched/ext.c

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20

kernel/sched/ext_cid.c

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10

kernel/sched/ext_internal.h

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52

tools/sched_ext/include/scx/cid.bpf.h

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5

tools/sched_ext/scx_qmap.bpf.c

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