Re: [PATCH] perf: arm_spe: Support heterogeneous ACPI systems

[Johnny Fan <johnny.fan@cixtech.com>]

On Fri, Oct 16, 2026 at 11:05:38AM +0100, Leo Yan wrote:
> SPE driver supports heterogeneous systems. If firmware creates proper
> devices based on CPU topology, the driver can probe multiple instances.
> 
> So "registration is limited to homogeneous systems" is not quite right.

You are right, I meant the ACPI registration path in arm_pmu_acpi.c. It
registers a single static SPE device, and only if every possible CPU
agrees on both the implementation tag (hetid) and the SPE interrupt
number -- a CPU that does not implement SPE reports 0, which breaks that
agreement, so a heterogeneous machine gets no SPE device at all (the
boot still succeeds; SPE is just absent). As Jeremy pointed out, the fix
is to group the CPUs by (hetid, GSIV) and create one device per group,
like DT does with PPI partitions. The driver already handles multiple
instances; how each one gets its supported_cpus is the plumbing question
I asked Marc about.


Thanks,

Johnny