[patch 48/53] x86/cpu/topology: Retrieve cores per package from topology bitmaps

Thomas Gleixner
2023-08-07T13:56:38Z

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: Thomas Gleixner <tglx@linutronix.de>
---
arch/x86/kernel/cpu/topology.c | 43 ++++++++++++++++++++++++++++++++++
arch/x86/kernel/cpu/topology.h | 3 ++
arch/x86/kernel/cpu/topology_common.c | 18 ++------------
3 files changed, 49 insertions(+), 15 deletions(-)

--- a/arch/x86/kernel/cpu/topology.c
+++ b/arch/x86/kernel/cpu/topology.c
@@ -227,6 +227,49 @@ int topology_get_logical_id(u32 apicid,
}
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
--- a/arch/x86/kernel/cpu/topology.h
+++ b/arch/x86/kernel/cpu/topology.h
@@ -50,4 +50,7 @@ static inline void topology_update_dom(s

extern const char *domain_names[TOPO_MAX_DOMAIN];

+unsigned int topology_unit_count(u32 apicid, enum x86_topology_domains which_units,
+ enum x86_topology_domains at_level);
+
#endif /* ARCH_X86_TOPOLOGY_H */
--- a/arch/x86/kernel/cpu/topology_common.c
+++ b/arch/x86/kernel/cpu/topology_common.c
@@ -154,25 +154,15 @@ static void topo_set_ids(struct topo_sca
/* Relative core ID */
c->topo.core_id = topo_relative_domain_id(apicid, TOPO_CORE_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_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];
-}
-
void cpu_parse_topology(struct cpuinfo_x86 *c)
{
unsigned int dom, cpu = smp_processor_id();
@@ -198,7 +188,6 @@ void cpu_parse_topology(struct cpuinfo_x
}

topo_set_ids(&tscan);
- topo_set_max_cores(&tscan);
}

void __init cpu_init_topology(struct cpuinfo_x86 *c)
@@ -220,7 +209,6 @@ void __init cpu_init_topology(struct cpu
}

topo_set_ids(&tscan);
- topo_set_max_cores(&tscan);

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