Commit 3205c983 authored by Thomas Gleixner's avatar Thomas Gleixner
Browse files

x86/cpu/topology: Retrieve cores per package from topology bitmaps 



Similar to other sizing information the number of cores per package can be
established from the topology bitmap.

Provide a function for retrieving that information and replace the buggy
hack in the CPUID evaluation with it.

Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Tested-by: default avatarMichael Kelley <mhklinux@outlook.com>
Tested-by: default avatarSohil Mehta <sohil.mehta@intel.com>
Link: https://lore.kernel.org/r/20240213210252.956858282@linutronix.de
parent 380414be

arch/x86/kernel/cpu/topology.c

+43 −0
Original line number Diff line number Diff line
@@ -257,6 +257,49 @@ int topology_get_logical_id(u32 apicid, enum x86_topology_domains at_level) 
}

EXPORT_SYMBOL_GPL(topology_get_logical_id);



/**

 * topology_unit_count - Retrieve the count of specified units at a given topology domain level

 * @apicid:		The APIC ID which specifies the search range

 * @which_units:	The domain level specifying the units to count

 * @at_level:		The domain level at which @which_units have to be counted

 *

 * This returns the number of possible units according to the enumerated

 * information.

 *

 * E.g. topology_count_units(apicid, TOPO_CORE_DOMAIN, TOPO_PKG_DOMAIN)

 * counts the number of possible cores in the package to which @apicid

 * belongs.

 *

 * @at_level must obviously be greater than @which_level to produce useful

 * results.  If @at_level is equal to @which_units the result is

 * unsurprisingly 1. If @at_level is less than @which_units the results

 * is by definition undefined and the function returns 0.

 */

unsigned int topology_unit_count(u32 apicid, enum x86_topology_domains which_units,

				 enum x86_topology_domains at_level)

{

	/* Remove the bits below @at_level to get the proper level ID of @apicid */

	unsigned int lvlid = topo_apicid(apicid, at_level);

	unsigned int id, end, cnt = 0;



	if (lvlid >= MAX_LOCAL_APIC)

		return 0;

	if (!test_bit(lvlid, apic_maps[at_level].map))

		return 0;

	if (which_units > at_level)

		return 0;

	if (which_units == at_level)

		return 1;



	/* Calculate the exclusive end */

	end = lvlid + (1U << x86_topo_system.dom_shifts[at_level]);

	/* Unfortunately there is no bitmap_weight_range() */

	for (id = find_next_bit(apic_maps[which_units].map, end, lvlid);

	     id < end; id = find_next_bit(apic_maps[which_units].map, end, ++id))

		cnt++;

	return cnt;

}



#ifdef CONFIG_ACPI_HOTPLUG_CPU

/**

 * topology_hotplug_apic - Handle a physical hotplugged APIC after boot

arch/x86/kernel/cpu/topology.h

+11 −0
Original line number Diff line number Diff line
@@ -53,4 +53,15 @@ static inline void topology_update_dom(struct topo_scan *tscan, enum x86_topolog 
	tscan->dom_ncpus[dom] = ncpus;

}



#ifdef CONFIG_X86_LOCAL_APIC

unsigned int topology_unit_count(u32 apicid, enum x86_topology_domains which_units,

				 enum x86_topology_domains at_level);

#else

static inline unsigned int topology_unit_count(u32 apicid, enum x86_topology_domains which_units,

					       enum x86_topology_domains at_level)

{

	return 1;

}

#endif



#endif /* ARCH_X86_TOPOLOGY_H */

arch/x86/kernel/cpu/topology_common.c

+3 −15
Original line number Diff line number Diff line
@@ -155,25 +155,15 @@ static void topo_set_ids(struct topo_scan *tscan) 
	c->topo.core_id = (apicid & topo_domain_mask(TOPO_PKG_DOMAIN)) >>

		x86_topo_system.dom_shifts[TOPO_SMT_DOMAIN];



	/* Maximum number of cores on this package */

	c->x86_max_cores = topology_unit_count(apicid, TOPO_CORE_DOMAIN, TOPO_PKG_DOMAIN);



	c->topo.amd_node_id = tscan->amd_node_id;



	if (c->x86_vendor == X86_VENDOR_AMD)

		cpu_topology_fixup_amd(tscan);

}



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_DIEGRP_DOMAIN] = 24; 24 / 2 = 12 !!

	 *

	 * Cannot be fixed without further topology enumeration changes.

	 */

	tscan->c->x86_max_cores = tscan->dom_ncpus[TOPO_DIEGRP_DOMAIN] >>

		x86_topo_system.dom_shifts[TOPO_SMT_DOMAIN];

}



void cpu_parse_topology(struct cpuinfo_x86 *c)

{

	unsigned int dom, cpu = smp_processor_id();
@@ -201,7 +191,6 @@ void cpu_parse_topology(struct cpuinfo_x86 *c) 
	}



	topo_set_ids(&tscan);

	topo_set_max_cores(&tscan);

}



void __init cpu_init_topology(struct cpuinfo_x86 *c)
@@ -223,7 +212,6 @@ void __init cpu_init_topology(struct cpuinfo_x86 *c) 
	}



	topo_set_ids(&tscan);

	topo_set_max_cores(&tscan);



	/*

	 * AMD systems have Nodes per package which cannot be mapped to