cpucheck.c

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/* -*- linux-c -*- ------------------------------------------------------- *
 *
 *   Copyright (C) 1991, 1992 Linus Torvalds
 *   Copyright 2007 rPath, Inc. - All Rights Reserved
 *
 *   This file is part of the Linux kernel, and is made available under
 *   the terms of the GNU General Public License version 2.
 *
 * ----------------------------------------------------------------------- */

/*
 * Check for obligatory CPU features and abort if the features are not
 * present.  This code should be compilable as 16-, 32- or 64-bit
 * code, so be very careful with types and inline assembly.
 *
 * This code should not contain any messages; that requires an
 * additional wrapper.
 *
 * As written, this code is not safe for inclusion into the kernel
 * proper (after FPU initialization, in particular).
 */

#ifdef _SETUP
# include "boot.h"
#endif
#include <linux/types.h>
#include <asm/processor-flags.h>
#include <asm/required-features.h>
#include <asm/msr-index.h>

struct cpu_features cpu;
static u32 cpu_vendor[3];
static u32 err_flags[NCAPINTS];

static const int req_level = CONFIG_X86_MINIMUM_CPU_FAMILY;

static const u32 req_flags[NCAPINTS] =
{
    REQUIRED_MASK0,
    REQUIRED_MASK1,
    0, /* REQUIRED_MASK2 not implemented in this file */
    0, /* REQUIRED_MASK3 not implemented in this file */
    REQUIRED_MASK4,
    0, /* REQUIRED_MASK5 not implemented in this file */
    REQUIRED_MASK6,
    0, /* REQUIRED_MASK7 not implemented in this file */
};

#define A32(a, b, c, d) (((d) << 24)+((c) << 16)+((b) << 8)+(a))

static int is_amd(void)
{
    return cpu_vendor[0] == A32('A', 'u', 't', 'h') &&
           cpu_vendor[1] == A32('e', 'n', 't', 'i') &&
           cpu_vendor[2] == A32('c', 'A', 'M', 'D');
}

static int is_centaur(void)
{
    return cpu_vendor[0] == A32('C', 'e', 'n', 't') &&
           cpu_vendor[1] == A32('a', 'u', 'r', 'H') &&
           cpu_vendor[2] == A32('a', 'u', 'l', 's');
}

static int is_transmeta(void)
{
    return cpu_vendor[0] == A32('G', 'e', 'n', 'u') &&
           cpu_vendor[1] == A32('i', 'n', 'e', 'T') &&
           cpu_vendor[2] == A32('M', 'x', '8', '6');
}

static int has_fpu(void)
{
    u16 fcw = -1, fsw = -1;
    u32 cr0;

    asm("movl %%cr0,%0" : "=r" (cr0));
    if (cr0 & (X86_CR0_EM|X86_CR0_TS)) {
        cr0 &= ~(X86_CR0_EM|X86_CR0_TS);
        asm volatile("movl %0,%%cr0" : : "r" (cr0));
    }

    asm volatile("fninit ; fnstsw %0 ; fnstcw %1"
             : "+m" (fsw), "+m" (fcw));

    return fsw == 0 && (fcw & 0x103f) == 0x003f;
}

static int has_eflag(u32 mask)
{
    u32 f0, f1;

    asm("pushfl ; "
        "pushfl ; "
        "popl %0 ; "
        "movl %0,%1 ; "
        "xorl %2,%1 ; "
        "pushl %1 ; "
        "popfl ; "
        "pushfl ; "
        "popl %1 ; "
        "popfl"
        : "=&r" (f0), "=&r" (f1)
        : "ri" (mask));

    return !!((f0^f1) & mask);
}

static void get_flags(void)
{
    u32 max_intel_level, max_amd_level;
    u32 tfms;

    if (has_fpu())
        set_bit(X86_FEATURE_FPU, cpu.flags);

    if (has_eflag(X86_EFLAGS_ID)) {
        asm("cpuid"
            : "=a" (max_intel_level),
              "=b" (cpu_vendor[0]),
              "=d" (cpu_vendor[1]),
              "=c" (cpu_vendor[2])
            : "a" (0));

        if (max_intel_level >= 0x00000001 &&
            max_intel_level <= 0x0000ffff) {
            asm("cpuid"
                : "=a" (tfms),
                  "=c" (cpu.flags[4]),
                  "=d" (cpu.flags[0])
                : "a" (0x00000001)
                : "ebx");
            cpu.level = (tfms >> 8) & 15;
            cpu.model = (tfms >> 4) & 15;
            if (cpu.level >= 6)
                cpu.model += ((tfms >> 16) & 0xf) << 4;
        }

        asm("cpuid"
            : "=a" (max_amd_level)
            : "a" (0x80000000)
            : "ebx", "ecx", "edx");

        if (max_amd_level >= 0x80000001 &&
            max_amd_level <= 0x8000ffff) {
            u32 eax = 0x80000001;
            asm("cpuid"
                : "+a" (eax),
                  "=c" (cpu.flags[6]),
                  "=d" (cpu.flags[1])
                : : "ebx");
        }
    }
}

/* Returns a bitmask of which words we have error bits in */
static int check_flags(void)
{
    u32 err;
    int i;

    err = 0;
    for (i = 0; i < NCAPINTS; i++) {
        err_flags[i] = req_flags[i] & ~cpu.flags[i];
        if (err_flags[i])
            err |= 1 << i;
    }

    return err;
}

/*
 * Returns -1 on error.
 *
 * *cpu_level is set to the current CPU level; *req_level to the required
 * level.  x86-64 is considered level 64 for this purpose.
 *
 * *err_flags_ptr is set to the flags error array if there are flags missing.
 */
int check_cpu(int *cpu_level_ptr, int *req_level_ptr, u32 **err_flags_ptr)
{
    int err;

    memset(&cpu.flags, 0, sizeof cpu.flags);
    cpu.level = 3;

    if (has_eflag(X86_EFLAGS_AC))
        cpu.level = 4;

    get_flags();
    err = check_flags();

    if (test_bit(X86_FEATURE_LM, cpu.flags))
        cpu.level = 64;

    if (err == 0x01 &&
        !(err_flags[0] &
          ~((1 << X86_FEATURE_XMM)|(1 << X86_FEATURE_XMM2))) &&
        is_amd()) {
        /* If this is an AMD and we're only missing SSE+SSE2, try to
           turn them on */

        u32 ecx = MSR_K7_HWCR;
        u32 eax, edx;

        asm("rdmsr" : "=a" (eax), "=d" (edx) : "c" (ecx));
        eax &= ~(1 << 15);
        asm("wrmsr" : : "a" (eax), "d" (edx), "c" (ecx));

        get_flags();    /* Make sure it really did something */
        err = check_flags();
    } else if (err == 0x01 &&
           !(err_flags[0] & ~(1 << X86_FEATURE_CX8)) &&
           is_centaur() && cpu.model >= 6) {
        /* If this is a VIA C3, we might have to enable CX8
           explicitly */

        u32 ecx = MSR_VIA_FCR;
        u32 eax, edx;

        asm("rdmsr" : "=a" (eax), "=d" (edx) : "c" (ecx));
        eax |= (1<<1)|(1<<7);
        asm("wrmsr" : : "a" (eax), "d" (edx), "c" (ecx));

        set_bit(X86_FEATURE_CX8, cpu.flags);
        err = check_flags();
    } else if (err == 0x01 && is_transmeta()) {
        /* Transmeta might have masked feature bits in word 0 */

        u32 ecx = 0x80860004;
        u32 eax, edx;
        u32 level = 1;

        asm("rdmsr" : "=a" (eax), "=d" (edx) : "c" (ecx));
        asm("wrmsr" : : "a" (~0), "d" (edx), "c" (ecx));
        asm("cpuid"
            : "+a" (level), "=d" (cpu.flags[0])
            : : "ecx", "ebx");
        asm("wrmsr" : : "a" (eax), "d" (edx), "c" (ecx));

        err = check_flags();
    }

    if (err_flags_ptr)
        *err_flags_ptr = err ? err_flags : NULL;
    if (cpu_level_ptr)
        *cpu_level_ptr = cpu.level;
    if (req_level_ptr)
        *req_level_ptr = req_level;

    return (cpu.level < req_level || err) ? -1 : 0;
}