Re: [patch V3 23/40] x86/cpu: Provide cpu_init/parse_topology()

[K Prateek Nayak]

Hello Thomas,

On 8/2/2023 3:51 PM, Thomas Gleixner wrote:
>
> [..snip..]
>
> +static void topo_set_max_cores(struct topo_scan *tscan)
> +{
> +	/*
> +	 * Bug compatible for now. This is broken on hybrid systems:
> +	 * 8 cores SMT + 8 cores w/o SMT
> +	 * tscan.dom_ncpus[TOPO_CORE_DOMAIN] = 24; 24 / 2 = 12 !!
> +	 *
> +	 * Cannot be fixed without further topology enumeration changes.
> +	 */
> +	tscan->c->x86_max_cores = tscan->dom_ncpus[TOPO_CORE_DOMAIN] >>
> +		x86_topo_system.dom_shifts[TOPO_SMT_DOMAIN];
> +}
>

In Documentation/arch/x86/topology.rst, "cpuinfo_x86.x86_max_cores" is
described as "The number of cores in a package". In which case,
shouldn't the above be:

	tscan->c->x86_max_cores = tscan->dom_ncpus[TOPO_PKG_DOMAIN] >>
		x86_topo_system.dom_shifts[TOPO_SMT_DOMAIN];

since, with extended topology, there could be other higher domains and
dom_ncpus[TOPO_CORE_DOMAIN] >> dom_shifts[TOPO_SMT_DOMAIN] should only
give number of cores within the next domain (TOPO_MODULE_DOMAIN).

Am I missing something here?

--
Thanks and Regards,
Prateek