2 * Copyright (C) 1994 Linus Torvalds
4 * Cyrix stuff, June 1998 by:
5 * - Rafael R. Reilova (moved everything from head.S),
6 * <rreilova@ececs.uc.edu>
7 * - Channing Corn (tests & fixes),
8 * - Andrew D. Balsa (code cleanup).
10 #include <linux/init.h>
11 #include <linux/utsname.h>
13 #include <asm/processor.h>
14 #include <asm/processor-flags.h>
17 #include <asm/paravirt.h>
18 #include <asm/alternative.h>
20 static int __init no_halt(char *s)
22 boot_cpu_data.hlt_works_ok = 0;
26 __setup("no-hlt", no_halt);
28 static int __init no_387(char *s)
30 boot_cpu_data.hard_math = 0;
31 write_cr0(X86_CR0_TS | X86_CR0_EM | X86_CR0_MP | read_cr0());
35 __setup("no387", no_387);
37 static double __initdata x = 4195835.0;
38 static double __initdata y = 3145727.0;
41 * This used to check for exceptions..
42 * However, it turns out that to support that,
43 * the XMM trap handlers basically had to
44 * be buggy. So let's have a correct XMM trap
45 * handler, and forget about printing out
46 * some status at boot.
48 * We should really only care about bugs here
49 * anyway. Not features.
51 static void __init check_fpu(void)
53 if (!boot_cpu_data.hard_math) {
54 #ifndef CONFIG_MATH_EMULATION
55 printk(KERN_EMERG "No coprocessor found and no math emulation present.\n");
56 printk(KERN_EMERG "Giving up.\n");
62 /* trap_init() enabled FXSR and company _before_ testing for FP problems here. */
63 /* Test for the divl bug.. */
69 "fsubp %%st,%%st(1)\n\t"
73 : "=m" (*&boot_cpu_data.fdiv_bug)
74 : "m" (*&x), "m" (*&y));
75 if (boot_cpu_data.fdiv_bug)
76 printk("Hmm, FPU with FDIV bug.\n");
79 static void __init check_hlt(void)
81 if (paravirt_enabled())
84 printk(KERN_INFO "Checking 'hlt' instruction... ");
85 if (!boot_cpu_data.hlt_works_ok) {
97 * Most 386 processors have a bug where a POPAD can lock the
98 * machine even from user space.
101 static void __init check_popad(void)
103 #ifndef CONFIG_X86_POPAD_OK
104 int res, inp = (int) &res;
106 printk(KERN_INFO "Checking for popad bug... ");
107 __asm__ __volatile__(
108 "movl $12345678,%%eax; movl $0,%%edi; pusha; popa; movl (%%edx,%%edi),%%ecx "
112 /* If this fails, it means that any user program may lock the CPU hard. Too bad. */
113 if (res != 12345678) printk( "Buggy.\n" );
114 else printk( "OK.\n" );
119 * Check whether we are able to run this kernel safely on SMP.
121 * - In order to run on a i386, we need to be compiled for i386
122 * (for due to lack of "invlpg" and working WP on a i386)
123 * - In order to run on anything without a TSC, we need to be
124 * compiled for a i486.
125 * - In order to support the local APIC on a buggy Pentium machine,
126 * we need to be compiled with CONFIG_X86_GOOD_APIC disabled,
127 * which happens implicitly if compiled for a Pentium or lower
128 * (unless an advanced selection of CPU features is used) as an
129 * otherwise config implies a properly working local APIC without
130 * the need to do extra reads from the APIC.
133 static void __init check_config(void)
136 * We'd better not be a i386 if we're configured to use some
137 * i486+ only features! (WP works in supervisor mode and the
138 * new "invlpg" and "bswap" instructions)
140 #if defined(CONFIG_X86_WP_WORKS_OK) || defined(CONFIG_X86_INVLPG) || defined(CONFIG_X86_BSWAP)
141 if (boot_cpu_data.x86 == 3)
142 panic("Kernel requires i486+ for 'invlpg' and other features");
146 * If we were told we had a good local APIC, check for buggy Pentia,
147 * i.e. all B steppings and the C2 stepping of P54C when using their
148 * integrated APIC (see 11AP erratum in "Pentium Processor
149 * Specification Update").
151 #if defined(CONFIG_X86_LOCAL_APIC) && defined(CONFIG_X86_GOOD_APIC)
152 if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL
154 && boot_cpu_data.x86 == 5
155 && boot_cpu_data.x86_model == 2
156 && (boot_cpu_data.x86_mask < 6 || boot_cpu_data.x86_mask == 11))
157 panic("Kernel compiled for PMMX+, assumes a local APIC without the read-before-write bug!");
162 void __init check_bugs(void)
167 print_cpu_info(&boot_cpu_data);
173 init_utsname()->machine[1] = '0' + (boot_cpu_data.x86 > 6 ? 6 : boot_cpu_data.x86);
174 alternative_instructions();