[RFC 11/12] keys/mktme: Add a new key service type for memory encryption keys

[Alison Schofield]

On Sun, Sep 09, 2018 at 08:29:29PM -0700, Huang, Kai wrote:
> > + */
> > +static int mktme_build_cpumask(void)
> > +{
> > +	int online_cpu, mktme_cpu;
> > +	int online_pkgid, mktme_pkgid = -1;
> > +
> > +	if (!zalloc_cpumask_var(&mktme_cpumask, GFP_KERNEL))
> > +		return -ENOMEM;
> > +
> > +	for_each_online_cpu(online_cpu) {
> > +		online_pkgid = topology_physical_package_id(online_cpu);
> > +
> > +		for_each_cpu(mktme_cpu, mktme_cpumask) {
> > +			mktme_pkgid =
> > topology_physical_package_id(mktme_cpu);
> > +			if (mktme_pkgid == online_pkgid)
> > +				break;
> > +		}
> > +		if (mktme_pkgid != online_pkgid)
> > +			cpumask_set_cpu(online_cpu, mktme_cpumask);
> > +	}
> 
> Could we use 'for_each_online_node', 'cpumask_first/next', etc to simplify the logic?

Kai, 

I tried to simplify it and came up with code that looked like this:

	int lead_cpu, node;
	for_each_online_node(node) {
		lead_cpu = cpumask_first(cpumask_of_node(node));
		if (lead_cpu < nr_cpu_ids)
			cpumask_set_cpu(lead_cpu, mktme_cpumask_NEW);
	}
When I test it on an SNC (Sub Numa Cluster) system it gives me too many
CPU's. I get a CPU per Node (just like i asked for;) instead of per Socket.
It has 2 sockets and 4 NUMA nodes. 

I kind of remember this when I originally coded it, hence the bottoms up
approach using topology_physical_package_id()

Any ideas?

Alison