[RFC PATCH 1/3] arm64: add CPU prefetch and cache modulation sysfs interface

[KobaK]

Hi Breno,

Thanks for reviewing and testing this.

The current read result is consumed by cpumod_attr_show(), but you are right
that the persistent cached-value plumbing is unnecessary. For v2, I plan to
return the value through call.value, emit it directly, and remove the cached
fields and helpers that no longer have a consumer.

I also agree about the permissions issue. The register-backed reads perform a
synchronous IPI, so allowing unprivileged reads could generate a steady IPI
stream. I plan to change the six register-backed controls to 0600 and retain
affected_cpus as 0444 metadata.

I have recorded your Tested-by, but I will confirm that it still applies after
these changes before carrying it into v2. The resend is currently on hold
pending arm64 maintainer direction.

Thanks,
Koba