topology.c

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/*
 * Check for extended topology enumeration cpuid leaf 0xb and if it
 * exists, use it for populating initial_apicid and cpu topology
 * detection.
 */

#include <linux/cpu.h>
#include <asm/apic.h>
#include <asm/pat.h>
#include <asm/processor.h>

/* leaf 0xb SMT level */
#define SMT_LEVEL   0

/* leaf 0xb sub-leaf types */
#define INVALID_TYPE    0
#define SMT_TYPE    1
#define CORE_TYPE   2

#define LEAFB_SUBTYPE(ecx)      (((ecx) >> 8) & 0xff)
#define BITS_SHIFT_NEXT_LEVEL(eax)  ((eax) & 0x1f)
#define LEVEL_MAX_SIBLINGS(ebx)     ((ebx) & 0xffff)

/*
 * Check for extended topology enumeration cpuid leaf 0xb and if it
 * exists, use it for populating initial_apicid and cpu topology
 * detection.
 */
void __cpuinit detect_extended_topology(struct cpuinfo_x86 *c)
{
#ifdef CONFIG_SMP
    unsigned int eax, ebx, ecx, edx, sub_index;
    unsigned int ht_mask_width, core_plus_mask_width;
    unsigned int core_select_mask, core_level_siblings;
    static bool printed;

    if (c->cpuid_level < 0xb)
        return;

    cpuid_count(0xb, SMT_LEVEL, &eax, &ebx, &ecx, &edx);

    /*
     * check if the cpuid leaf 0xb is actually implemented.
     */
    if (ebx == 0 || (LEAFB_SUBTYPE(ecx) != SMT_TYPE))
        return;

    set_cpu_cap(c, X86_FEATURE_XTOPOLOGY);

    /*
     * initial apic id, which also represents 32-bit extended x2apic id.
     */
    c->initial_apicid = edx;

    /*
     * Populate HT related information from sub-leaf level 0.
     */
    core_level_siblings = smp_num_siblings = LEVEL_MAX_SIBLINGS(ebx);
    core_plus_mask_width = ht_mask_width = BITS_SHIFT_NEXT_LEVEL(eax);

    sub_index = 1;
    do {
        cpuid_count(0xb, sub_index, &eax, &ebx, &ecx, &edx);

        /*
         * Check for the Core type in the implemented sub leaves.
         */
        if (LEAFB_SUBTYPE(ecx) == CORE_TYPE) {
            core_level_siblings = LEVEL_MAX_SIBLINGS(ebx);
            core_plus_mask_width = BITS_SHIFT_NEXT_LEVEL(eax);
            break;
        }

        sub_index++;
    } while (LEAFB_SUBTYPE(ecx) != INVALID_TYPE);

    core_select_mask = (~(-1 << core_plus_mask_width)) >> ht_mask_width;

    c->cpu_core_id = apic->phys_pkg_id(c->initial_apicid, ht_mask_width)
                         & core_select_mask;
    c->phys_proc_id = apic->phys_pkg_id(c->initial_apicid, core_plus_mask_width);
    /*
     * Reinit the apicid, now that we have extended initial_apicid.
     */
    c->apicid = apic->phys_pkg_id(c->initial_apicid, 0);

    c->x86_max_cores = (core_level_siblings / smp_num_siblings);

    if (!printed) {
        printk(KERN_INFO  "CPU: Physical Processor ID: %d\n",
               c->phys_proc_id);
        if (c->x86_max_cores > 1)
            printk(KERN_INFO  "CPU: Processor Core ID: %d\n",
                   c->cpu_core_id);
        printed = 1;
    }
    return;
#endif
}