1/*
2 *  include/asm-i386/bugs.h
3 *
4 *  Copyright (C) 1994  Linus Torvalds
5 *
6 *  Cyrix stuff, June 1998 by:
7 *	- Rafael R. Reilova (moved everything from head.S),
8 *        <rreilova@ececs.uc.edu>
9 *	- Channing Corn (tests & fixes),
10 *	- Andrew D. Balsa (code cleanup).
11 *
12 *  Pentium III FXSR, SSE support
13 *	Gareth Hughes <gareth@valinux.com>, May 2000
14 */
15
16/*
17 * This is included by init/main.c to check for architecture-dependent bugs.
18 *
19 * Needs:
20 *	void check_bugs(void);
21 */
22
23#include <linux/config.h>
24#include <asm/processor.h>
25#include <asm/i387.h>
26#include <asm/msr.h>
27
28static int __init no_halt(char *s)
29{
30	boot_cpu_data.hlt_works_ok = 0;
31	return 1;
32}
33
34__setup("no-hlt", no_halt);
35
36static int __init mca_pentium(char *s)
37{
38	mca_pentium_flag = 1;
39	return 1;
40}
41
42__setup("mca-pentium", mca_pentium);
43
44static int __init no_387(char *s)
45{
46	boot_cpu_data.hard_math = 0;
47	write_cr0(0xE | read_cr0());
48	return 1;
49}
50
51__setup("no387", no_387);
52
53static double __initdata x = 4195835.0;
54static double __initdata y = 3145727.0;
55
56/*
57 * This used to check for exceptions..
58 * However, it turns out that to support that,
59 * the XMM trap handlers basically had to
60 * be buggy. So let's have a correct XMM trap
61 * handler, and forget about printing out
62 * some status at boot.
63 *
64 * We should really only care about bugs here
65 * anyway. Not features.
66 */
67static void __init check_fpu(void)
68{
69	if (!boot_cpu_data.hard_math) {
70#ifndef CONFIG_MATH_EMULATION
71		printk(KERN_EMERG "No coprocessor found and no math emulation present.\n");
72		printk(KERN_EMERG "Giving up.\n");
73		for (;;) ;
74#endif
75		return;
76	}
77
78/* Enable FXSR and company _before_ testing for FP problems. */
79	/*
80	 * Verify that the FXSAVE/FXRSTOR data will be 16-byte aligned.
81	 */
82	if (offsetof(struct task_struct, thread.i387.fxsave) & 15) {
83		extern void __buggy_fxsr_alignment(void);
84		__buggy_fxsr_alignment();
85	}
86	if (cpu_has_fxsr) {
87		printk(KERN_INFO "Enabling fast FPU save and restore... ");
88		set_in_cr4(X86_CR4_OSFXSR);
89		printk("done.\n");
90	}
91	if (cpu_has_xmm) {
92		printk(KERN_INFO "Enabling unmasked SIMD FPU exception support... ");
93		set_in_cr4(X86_CR4_OSXMMEXCPT);
94		printk("done.\n");
95	}
96
97	/* Test for the divl bug.. */
98	__asm__("fninit\n\t"
99		"fldl %1\n\t"
100		"fdivl %2\n\t"
101		"fmull %2\n\t"
102		"fldl %1\n\t"
103		"fsubp %%st,%%st(1)\n\t"
104		"fistpl %0\n\t"
105		"fwait\n\t"
106		"fninit"
107		: "=m" (*&boot_cpu_data.fdiv_bug)
108		: "m" (*&x), "m" (*&y));
109	if (boot_cpu_data.fdiv_bug)
110		printk("Hmm, FPU with FDIV bug.\n");
111}
112
113static void __init check_hlt(void)
114{
115	printk(KERN_INFO "Checking 'hlt' instruction... ");
116	if (!boot_cpu_data.hlt_works_ok) {
117		printk("disabled\n");
118		return;
119	}
120	__asm__ __volatile__("hlt ; hlt ; hlt ; hlt");
121	printk("OK.\n");
122}
123
124/*
125 *	Most 386 processors have a bug where a POPAD can lock the
126 *	machine even from user space.
127 */
128
129static void __init check_popad(void)
130{
131#ifndef CONFIG_X86_POPAD_OK
132	int res, inp = (int) &res;
133
134	printk(KERN_INFO "Checking for popad bug... ");
135	__asm__ __volatile__(
136	  "movl $12345678,%%eax; movl $0,%%edi; pusha; popa; movl (%%edx,%%edi),%%ecx "
137	  : "=&a" (res)
138	  : "d" (inp)
139	  : "ecx", "edi" );
140	/* If this fails, it means that any user program may lock the CPU hard. Too bad. */
141	if (res != 12345678) printk( "Buggy.\n" );
142		        else printk( "OK.\n" );
143#endif
144}
145
146/*
147 * Check whether we are able to run this kernel safely on SMP.
148 *
149 * - In order to run on a i386, we need to be compiled for i386
150 *   (for due to lack of "invlpg" and working WP on a i386)
151 * - In order to run on anything without a TSC, we need to be
152 *   compiled for a i486.
153 * - In order to support the local APIC on a buggy Pentium machine,
154 *   we need to be compiled with CONFIG_X86_GOOD_APIC disabled,
155 *   which happens implicitly if compiled for a Pentium or lower
156 *   (unless an advanced selection of CPU features is used) as an
157 *   otherwise config implies a properly working local APIC without
158 *   the need to do extra reads from the APIC.
159*/
160
161static void __init check_config(void)
162{
163/*
164 * We'd better not be a i386 if we're configured to use some
165 * i486+ only features! (WP works in supervisor mode and the
166 * new "invlpg" and "bswap" instructions)
167 */
168#if defined(CONFIG_X86_WP_WORKS_OK) || defined(CONFIG_X86_INVLPG) || defined(CONFIG_X86_BSWAP)
169	if (boot_cpu_data.x86 == 3)
170		panic("Kernel requires i486+ for 'invlpg' and other features");
171#endif
172
173/*
174 * If we configured ourselves for a TSC, we'd better have one!
175 */
176#ifdef CONFIG_X86_TSC
177	if (!cpu_has_tsc)
178		panic("Kernel compiled for Pentium+, requires TSC feature!");
179#endif
180
181/*
182 * If we configured ourselves for PGE, we'd better have it.
183 */
184#ifdef CONFIG_X86_PGE
185	if (!cpu_has_pge)
186		panic("Kernel compiled for PPro+, requires PGE feature!");
187#endif
188
189/*
190 * If we were told we had a good local APIC, check for buggy Pentia,
191 * i.e. all B steppings and the C2 stepping of P54C when using their
192 * integrated APIC (see 11AP erratum in "Pentium Processor
193 * Specification Update").
194 */
195#if defined(CONFIG_X86_LOCAL_APIC) && defined(CONFIG_X86_GOOD_APIC)
196	if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL
197	    && test_bit(X86_FEATURE_APIC, &boot_cpu_data.x86_capability)
198	    && boot_cpu_data.x86 == 5
199	    && boot_cpu_data.x86_model == 2
200	    && (boot_cpu_data.x86_mask < 6 || boot_cpu_data.x86_mask == 11))
201		panic("Kernel compiled for PMMX+, assumes a local APIC without the read-before-write bug!");
202#endif
203}
204
205static void __init check_bugs(void)
206{
207	extern void __init boot_init_fpu(void);
208
209	identify_cpu(&boot_cpu_data);
210	boot_init_fpu();
211#ifndef CONFIG_SMP
212	printk("CPU: ");
213	print_cpu_info(&boot_cpu_data);
214#endif
215	check_config();
216	check_fpu();
217	check_hlt();
218	check_popad();
219	system_utsname.machine[1] = '0' + (boot_cpu_data.x86 > 6 ? 6 : boot_cpu_data.x86);
220}
221