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>
12 #include <linux/cpu.h>
14 #include <asm/processor.h>
15 #include <asm/processor-flags.h>
18 #include <asm/paravirt.h>
19 #include <asm/alternative.h>
20 #include <asm/pgtable.h>
21 #include <asm/cacheflush.h>
25 static int __init no_halt(char *s)
27 WARN_ONCE(1, "\"no-hlt\" is deprecated, please use \"idle=poll\"\n");
28 boot_cpu_data.hlt_works_ok = 0;
32 __setup("no-hlt", no_halt);
34 static int __init no_387(char *s)
36 boot_cpu_data.hard_math = 0;
37 write_cr0(X86_CR0_TS | X86_CR0_EM | X86_CR0_MP | read_cr0());
41 __setup("no387", no_387);
43 static double __initdata x = 4195835.0;
44 static double __initdata y = 3145727.0;
47 * This used to check for exceptions..
48 * However, it turns out that to support that,
49 * the XMM trap handlers basically had to
50 * be buggy. So let's have a correct XMM trap
51 * handler, and forget about printing out
52 * some status at boot.
54 * We should really only care about bugs here
55 * anyway. Not features.
57 static void __init check_fpu(void)
61 if (!boot_cpu_data.hard_math) {
62 #ifndef CONFIG_MATH_EMULATION
63 printk(KERN_EMERG "No coprocessor found and no math emulation present.\n");
64 printk(KERN_EMERG "Giving up.\n");
73 * trap_init() enabled FXSR and company _before_ testing for FP
76 * Test for the divl bug..
83 "fsubp %%st,%%st(1)\n\t"
88 : "m" (*&x), "m" (*&y));
92 boot_cpu_data.fdiv_bug = fdiv_bug;
93 if (boot_cpu_data.fdiv_bug)
94 printk(KERN_WARNING "Hmm, FPU with FDIV bug.\n");
97 static void __init check_hlt(void)
99 if (boot_cpu_data.x86 >= 5 || paravirt_enabled())
102 printk(KERN_INFO "Checking 'hlt' instruction... ");
103 if (!boot_cpu_data.hlt_works_ok) {
104 printk("disabled\n");
111 printk(KERN_CONT "OK.\n");
115 * Most 386 processors have a bug where a POPAD can lock the
116 * machine even from user space.
119 static void __init check_popad(void)
121 #ifndef CONFIG_X86_POPAD_OK
122 int res, inp = (int) &res;
124 printk(KERN_INFO "Checking for popad bug... ");
125 __asm__ __volatile__(
126 "movl $12345678,%%eax; movl $0,%%edi; pusha; popa; movl (%%edx,%%edi),%%ecx "
131 * If this fails, it means that any user program may lock the
135 printk(KERN_CONT "Buggy.\n");
137 printk(KERN_CONT "OK.\n");
142 * Check whether we are able to run this kernel safely on SMP.
144 * - In order to run on a i386, we need to be compiled for i386
145 * (for due to lack of "invlpg" and working WP on a i386)
146 * - In order to run on anything without a TSC, we need to be
147 * compiled for a i486.
150 static void __init check_config(void)
153 * We'd better not be a i386 if we're configured to use some
154 * i486+ only features! (WP works in supervisor mode and the
155 * new "invlpg" and "bswap" instructions)
157 #if defined(CONFIG_X86_WP_WORKS_OK) || defined(CONFIG_X86_INVLPG) || \
158 defined(CONFIG_X86_BSWAP)
159 if (boot_cpu_data.x86 == 3)
160 panic("Kernel requires i486+ for 'invlpg' and other features");
164 #endif /* CONFIG_X86_32 */
166 void __init check_bugs(void)
170 * Regardless of whether PCID is enumerated, the SDM says
171 * that it can't be enabled in 32-bit mode.
173 setup_clear_cpu_cap(X86_FEATURE_PCID);
178 if (!IS_ENABLED(CONFIG_SMP)) {
180 print_cpu_info(&boot_cpu_data);
188 init_utsname()->machine[1] =
189 '0' + (boot_cpu_data.x86 > 6 ? 6 : boot_cpu_data.x86);
190 alternative_instructions();
191 #else /* CONFIG_X86_64 */
192 alternative_instructions();
195 * Make sure the first 2MB area is not mapped by huge pages
196 * There are typically fixed size MTRRs in there and overlapping
197 * MTRRs into large pages causes slow downs.
199 * Right now we don't do that with gbpages because there seems
200 * very little benefit for that case.
203 set_memory_4k((unsigned long)__va(0), 1);
208 ssize_t cpu_show_meltdown(struct sysdev_class *dev,
209 struct sysdev_class_attribute *attr, char *buf)
211 if (!boot_cpu_has_bug(X86_BUG_CPU_MELTDOWN))
212 return sprintf(buf, "Not affected\n");
213 if (boot_cpu_has(X86_FEATURE_KAISER))
214 return sprintf(buf, "Mitigation: PTI\n");
215 return sprintf(buf, "Vulnerable\n");
218 ssize_t cpu_show_spectre_v1(struct sysdev_class *dev,
219 struct sysdev_class_attribute *attr, char *buf)
221 if (!boot_cpu_has_bug(X86_BUG_SPECTRE_V1))
222 return sprintf(buf, "Not affected\n");
223 return sprintf(buf, "Vulnerable\n");
226 ssize_t cpu_show_spectre_v2(struct sysdev_class *dev,
227 struct sysdev_class_attribute *attr, char *buf)
229 if (!boot_cpu_has_bug(X86_BUG_SPECTRE_V2))
230 return sprintf(buf, "Not affected\n");
231 return sprintf(buf, "Vulnerable\n");