summaryrefslogtreecommitdiffstats
path: root/arch/x86/kernel/cpu/bugs.c
blob: 92dfec986a48ec97ffb680002f22a56f5a7b9262 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
/*
 *  Copyright (C) 1994  Linus Torvalds
 *
 *  Cyrix stuff, June 1998 by:
 *	- Rafael R. Reilova (moved everything from head.S),
 *        <rreilova@ececs.uc.edu>
 *	- Channing Corn (tests & fixes),
 *	- Andrew D. Balsa (code cleanup).
 */
#include <linux/init.h>
#include <linux/utsname.h>
#include <asm/bugs.h>
#include <asm/processor.h>
#include <asm/processor-flags.h>
#include <asm/i387.h>
#include <asm/msr.h>
#include <asm/paravirt.h>
#include <asm/alternative.h>

static int __init no_halt(char *s)
{
	WARN_ONCE(1, "\"no-hlt\" is deprecated, please use \"idle=poll\"\n");
	boot_cpu_data.hlt_works_ok = 0;
	return 1;
}

__setup("no-hlt", no_halt);

static int __init no_387(char *s)
{
	boot_cpu_data.hard_math = 0;
	write_cr0(X86_CR0_TS | X86_CR0_EM | X86_CR0_MP | read_cr0());
	return 1;
}

__setup("no387", no_387);

static double __initdata x = 4195835.0;
static double __initdata y = 3145727.0;

/*
 * This used to check for exceptions..
 * However, it turns out that to support that,
 * the XMM trap handlers basically had to
 * be buggy. So let's have a correct XMM trap
 * handler, and forget about printing out
 * some status at boot.
 *
 * We should really only care about bugs here
 * anyway. Not features.
 */
static void __init check_fpu(void)
{
	s32 fdiv_bug;

	if (!boot_cpu_data.hard_math) {
#ifndef CONFIG_MATH_EMULATION
		pr_emerg("No coprocessor found and no math emulation present\n");
		pr_emerg("Giving up\n");
		for (;;) ;
#endif
		return;
	}

	kernel_fpu_begin();

	/*
	 * trap_init() enabled FXSR and company _before_ testing for FP
	 * problems here.
	 *
	 * Test for the divl bug..
	 */
	__asm__("fninit\n\t"
		"fldl %1\n\t"
		"fdivl %2\n\t"
		"fmull %2\n\t"
		"fldl %1\n\t"
		"fsubp %%st,%%st(1)\n\t"
		"fistpl %0\n\t"
		"fwait\n\t"
		"fninit"
		: "=m" (*&fdiv_bug)
		: "m" (*&x), "m" (*&y));

	kernel_fpu_end();

	boot_cpu_data.fdiv_bug = fdiv_bug;
	if (boot_cpu_data.fdiv_bug)
		pr_warn("Hmm, FPU with FDIV bug\n");
}

static void __init check_hlt(void)
{
	if (boot_cpu_data.x86 >= 5 || paravirt_enabled())
		return;

	pr_info("Checking 'hlt' instruction... ");
	if (!boot_cpu_data.hlt_works_ok) {
		pr_cont("disabled\n");
		return;
	}
	halt();
	halt();
	halt();
	halt();
	pr_cont("OK\n");
}

/*
 * Check whether we are able to run this kernel safely on SMP.
 *
 * - i386 is no longer supported.
 * - In order to run on anything without a TSC, we need to be
 *   compiled for a i486.
 */

static void __init check_config(void)
{
	if (boot_cpu_data.x86 < 4)
		panic("Kernel requires i486+ for 'invlpg' and other features");
}


void __init check_bugs(void)
{
	identify_boot_cpu();
#ifndef CONFIG_SMP
	pr_info("CPU: ");
	print_cpu_info(&boot_cpu_data);
#endif
	check_config();
	check_hlt();
	init_utsname()->machine[1] =
		'0' + (boot_cpu_data.x86 > 6 ? 6 : boot_cpu_data.x86);
	alternative_instructions();

	/*
	 * kernel_fpu_begin/end() in check_fpu() relies on the patched
	 * alternative instructions.
	 */
	check_fpu();
}
OpenPOWER on IntegriCloud