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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>
#include "string.h"
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 is_intel(void)
{
return cpu_vendor[0] == A32('G', 'e', 'n', 'u') &&
cpu_vendor[1] == A32('i', 'n', 'e', 'I') &&
cpu_vendor[2] == A32('n', 't', 'e', 'l');
}
/* Returns a bitmask of which words we have error bits in */
static int check_cpuflags(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_cpuflags();
err = check_cpuflags();
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_cpuflags(); /* Make sure it really did something */
err = check_cpuflags();
} 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_cpuflags();
} 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_cpuflags();
} else if (err == 0x01 &&
!(err_flags[0] & ~(1 << X86_FEATURE_PAE)) &&
is_intel() && cpu.level == 6 &&
(cpu.model == 9 || cpu.model == 13)) {
/* PAE is disabled on this Pentium M but can be forced */
if (cmdline_find_option_bool("forcepae")) {
puts("WARNING: Forcing PAE in CPU flags\n");
set_bit(X86_FEATURE_PAE, cpu.flags);
err = check_cpuflags();
}
else {
puts("WARNING: PAE disabled. Use parameter 'forcepae' to enable at your own risk!\n");
}
}
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;
}
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