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>
19 #include <asm/pgtable.h>
20 #include <asm/cacheflush.h>
24 static int __init no_halt(char *s)
26 WARN_ONCE(1, "\"no-hlt\" is deprecated, please use \"idle=poll\"\n");
27 boot_cpu_data.hlt_works_ok = 0;
31 __setup("no-hlt", no_halt);
33 static int __init no_387(char *s)
35 boot_cpu_data.hard_math = 0;
36 write_cr0(X86_CR0_TS | X86_CR0_EM | X86_CR0_MP | read_cr0());
40 __setup("no387", no_387);
42 static double __initdata x = 4195835.0;
43 static double __initdata y = 3145727.0;
46 * This used to check for exceptions..
47 * However, it turns out that to support that,
48 * the XMM trap handlers basically had to
49 * be buggy. So let's have a correct XMM trap
50 * handler, and forget about printing out
51 * some status at boot.
53 * We should really only care about bugs here
54 * anyway. Not features.
56 static void __init check_fpu(void)
60 if (!boot_cpu_data.hard_math) {
61 #ifndef CONFIG_MATH_EMULATION
62 printk(KERN_EMERG "No coprocessor found and no math emulation present.\n");
63 printk(KERN_EMERG "Giving up.\n");
72 * trap_init() enabled FXSR and company _before_ testing for FP
75 * Test for the divl bug..
82 "fsubp %%st,%%st(1)\n\t"
87 : "m" (*&x), "m" (*&y));
91 boot_cpu_data.fdiv_bug = fdiv_bug;
92 if (boot_cpu_data.fdiv_bug)
93 printk(KERN_WARNING "Hmm, FPU with FDIV bug.\n");
96 static void __init check_hlt(void)
98 if (boot_cpu_data.x86 >= 5 || paravirt_enabled())
101 printk(KERN_INFO "Checking 'hlt' instruction... ");
102 if (!boot_cpu_data.hlt_works_ok) {
103 printk("disabled\n");
110 printk(KERN_CONT "OK.\n");
114 * Most 386 processors have a bug where a POPAD can lock the
115 * machine even from user space.
118 static void __init check_popad(void)
120 #ifndef CONFIG_X86_POPAD_OK
121 int res, inp = (int) &res;
123 printk(KERN_INFO "Checking for popad bug... ");
124 __asm__ __volatile__(
125 "movl $12345678,%%eax; movl $0,%%edi; pusha; popa; movl (%%edx,%%edi),%%ecx "
130 * If this fails, it means that any user program may lock the
134 printk(KERN_CONT "Buggy.\n");
136 printk(KERN_CONT "OK.\n");
141 * Check whether we are able to run this kernel safely on SMP.
143 * - In order to run on a i386, we need to be compiled for i386
144 * (for due to lack of "invlpg" and working WP on a i386)
145 * - In order to run on anything without a TSC, we need to be
146 * compiled for a i486.
149 static void __init check_config(void)
152 * We'd better not be a i386 if we're configured to use some
153 * i486+ only features! (WP works in supervisor mode and the
154 * new "invlpg" and "bswap" instructions)
156 #if defined(CONFIG_X86_WP_WORKS_OK) || defined(CONFIG_X86_INVLPG) || \
157 defined(CONFIG_X86_BSWAP)
158 if (boot_cpu_data.x86 == 3)
159 panic("Kernel requires i486+ for 'invlpg' and other features");
163 #endif /* CONFIG_X86_32 */
165 void __init check_bugs(void)
169 * Regardless of whether PCID is enumerated, the SDM says
170 * that it can't be enabled in 32-bit mode.
172 setup_clear_cpu_cap(X86_FEATURE_PCID);
177 if (!IS_ENABLED(CONFIG_SMP)) {
179 print_cpu_info(&boot_cpu_data);
187 init_utsname()->machine[1] =
188 '0' + (boot_cpu_data.x86 > 6 ? 6 : boot_cpu_data.x86);
189 alternative_instructions();
190 #else /* CONFIG_X86_64 */
191 alternative_instructions();
194 * Make sure the first 2MB area is not mapped by huge pages
195 * There are typically fixed size MTRRs in there and overlapping
196 * MTRRs into large pages causes slow downs.
198 * Right now we don't do that with gbpages because there seems
199 * very little benefit for that case.
202 set_memory_4k((unsigned long)__va(0), 1);