sched_ext: Add shard boundaries to scx_bpf_cid_override()

An overridden cid mapping invalidates the auto-generated shard layout, so
the override call has to provide both. Extend scx_bpf_cid_override() with a
shard_start[] array that lists the first cid of each shard (starting at 0,
strictly increasing, last shard implicitly extends to num_possible_cpus()).

A scheduler that wants only custom shards with the auto-generated cid
mapping can read the current mapping and pass it back unchanged.

Overridden shards can span NUMA nodes, so scx_shard_node[] is rebuilt by
majority count: each shard is assigned to the node that owns the most cpus
in it.

v2: Snapshot the caller's cpu_to_cid/shard_start arrays before validating. (sashiko AI)

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

0 files changed, 0 insertions, 0 deletions