linux/arch/x86/kernel/cpu/topology_ext.c

// SPDX-License-Identifier: GPL-2.0
#include <linux/cpu.h>

#include <asm/apic.h>
#include <asm/memtype.h>
#include <asm/processor.h>

#include "cpu.h"

enum topo_types {
	INVALID_TYPE		= 0,
	SMT_TYPE		= 1,
	CORE_TYPE		= 2,
	MAX_TYPE_0B		= 3,
	MODULE_TYPE		= 3,
	TILE_TYPE		= 4,
	DIE_TYPE		= 5,
	DIEGRP_TYPE		= 6,
	MAX_TYPE_1F		= 7,
};

/*
 * Use a lookup table for the case that there are future types > 6 which
 * describe an intermediate domain level which does not exist today.
 */
static const unsigned int topo_domain_map_0b_1f[MAX_TYPE_1F] = {
	[SMT_TYPE]	= TOPO_SMT_DOMAIN,
	[CORE_TYPE]	= TOPO_CORE_DOMAIN,
	[MODULE_TYPE]	= TOPO_MODULE_DOMAIN,
	[TILE_TYPE]	= TOPO_TILE_DOMAIN,
	[DIE_TYPE]	= TOPO_DIE_DOMAIN,
	[DIEGRP_TYPE]	= TOPO_DIEGRP_DOMAIN,
};

static inline bool topo_subleaf(struct topo_scan *tscan, u32 leaf, u32 subleaf,
				unsigned int *last_dom)
{
	unsigned int dom, maxtype;
	const unsigned int *map;
	struct {
		// eax
		u32	x2apic_shift	:  5, // Number of bits to shift APIC ID right
					      // for the topology ID at the next level
					: 27; // Reserved
		// ebx
		u32	num_processors	: 16, // Number of processors at current level
					: 16; // Reserved
		// ecx
		u32	level		:  8, // Current topology level. Same as sub leaf number
			type		:  8, // Level type. If 0, invalid
					: 16; // Reserved
		// edx
		u32	x2apic_id	: 32; // X2APIC ID of the current logical processor
	} sl;

	switch (leaf) {
	case 0x0b: maxtype = MAX_TYPE_0B; map = topo_domain_map_0b_1f; break;
	case 0x1f: maxtype = MAX_TYPE_1F; map = topo_domain_map_0b_1f; break;
	default: return false;
	}

	cpuid_subleaf(leaf, subleaf, &sl);

	if (!sl.num_processors || sl.type == INVALID_TYPE)
		return false;

	if (sl.type >= maxtype) {
		pr_err_once("Topology: leaf 0x%x:%d Unknown domain type %u\n",
			    leaf, subleaf, sl.type);
		/*
		 * It really would have been too obvious to make the domain
		 * type space sparse and leave a few reserved types between
		 * the points which might change instead of following the
		 * usual "this can be fixed in software" principle.
		 */
		dom = *last_dom + 1;
	} else {
		dom = map[sl.type];
		*last_dom = dom;
	}

	if (!dom) {
		tscan->c->topo.initial_apicid = sl.x2apic_id;
	} else if (tscan->c->topo.initial_apicid != sl.x2apic_id) {
		pr_warn_once(FW_BUG "CPUID leaf 0x%x subleaf %d APIC ID mismatch %x != %x\n",
			     leaf, subleaf, tscan->c->topo.initial_apicid, sl.x2apic_id);
	}

	topology_set_dom(tscan, dom, sl.x2apic_shift, sl.num_processors);
	return true;
}

static bool parse_topology_leaf(struct topo_scan *tscan, u32 leaf)
{
	unsigned int last_dom;
	u32 subleaf;

	/* Read all available subleafs and populate the levels */
	for (subleaf = 0, last_dom = 0; topo_subleaf(tscan, leaf, subleaf, &last_dom); subleaf++);

	/* If subleaf 0 failed to parse, give up */
	if (!subleaf)
		return false;

	/*
	 * There are machines in the wild which have shift 0 in the subleaf
	 * 0, but advertise 2 logical processors at that level. They are
	 * truly SMT.
	 */
	if (!tscan->dom_shifts[TOPO_SMT_DOMAIN] && tscan->dom_ncpus[TOPO_SMT_DOMAIN] > 1) {
		unsigned int sft = get_count_order(tscan->dom_ncpus[TOPO_SMT_DOMAIN]);

		pr_warn_once(FW_BUG "CPUID leaf 0x%x subleaf 0 has shift level 0 but %u CPUs. Fixing it up.\n",
			     leaf, tscan->dom_ncpus[TOPO_SMT_DOMAIN]);
		topology_update_dom(tscan, TOPO_SMT_DOMAIN, sft, tscan->dom_ncpus[TOPO_SMT_DOMAIN]);
	}

	set_cpu_cap(tscan->c, X86_FEATURE_XTOPOLOGY);
	return true;
}

bool cpu_parse_topology_ext(struct topo_scan *tscan)
{
	/* Intel: Try leaf 0x1F first. */
	if (tscan->c->cpuid_level >= 0x1f && parse_topology_leaf(tscan, 0x1f))
		return true;

	/* Intel/AMD: Fall back to leaf 0xB if available */
	return tscan->c->cpuid_level >= 0x0b && parse_topology_leaf(tscan, 0x0b);
}