arch/x86/kernel/cpu/bugs.c

   1 /*
   2  *  Copyright (C) 1994  Linus Torvalds
   3  *
   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).
   9  */
  10 #include <linux/init.h>
  11 #include <linux/utsname.h>
  12 #include <asm/bugs.h>
  13 #include <asm/processor.h>
  14 #include <asm/i387.h>
  15 #include <asm/msr.h>
  16 #include <asm/paravirt.h>
  17 #include <asm/alternative.h>
  18
  19 static int __init no_halt(char *s)
  20 {
  21         boot_cpu_data.hlt_works_ok = 0;
  22         return 1;
  23 }
  24
  25 __setup("no-hlt", no_halt);
  26
  27 static int __init mca_pentium(char *s)
  28 {
  29         mca_pentium_flag = 1;
  30         return 1;
  31 }
  32
  33 __setup("mca-pentium", mca_pentium);
  34
  35 static int __init no_387(char *s)
  36 {
  37         boot_cpu_data.hard_math = 0;
  38         write_cr0(0xE | read_cr0());
  39         return 1;
  40 }
  41
  42 __setup("no387", no_387);
  43
  44 static double __initdata x = 4195835.0;
  45 static double __initdata y = 3145727.0;
  46
  47 /*
  48  * This used to check for exceptions..
  49  * However, it turns out that to support that,
  50  * the XMM trap handlers basically had to
  51  * be buggy. So let's have a correct XMM trap
  52  * handler, and forget about printing out
  53  * some status at boot.
  54  *
  55  * We should really only care about bugs here
  56  * anyway. Not features.
  57  */
  58 static void __init check_fpu(void)
  59 {
  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");
  64                 for (;;) ;
  65 #endif
  66                 return;
  67         }
  68
  69 /* trap_init() enabled FXSR and company _before_ testing for FP problems here. */
  70         /* Test for the divl bug.. */
  71         __asm__("fninit\n\t"
  72                 "fldl %1\n\t"
  73                 "fdivl %2\n\t"
  74                 "fmull %2\n\t"
  75                 "fldl %1\n\t"
  76                 "fsubp %%st,%%st(1)\n\t"
  77                 "fistpl %0\n\t"
  78                 "fwait\n\t"
  79                 "fninit"
  80                 : "=m" (*&boot_cpu_data.fdiv_bug)
  81                 : "m" (*&x), "m" (*&y));
  82         if (boot_cpu_data.fdiv_bug)
  83                 printk("Hmm, FPU with FDIV bug.\n");
  84 }
  85
  86 static void __init check_hlt(void)
  87 {
  88         if (paravirt_enabled())
  89                 return;
  90
  91         printk(KERN_INFO "Checking 'hlt' instruction... ");
  92         if (!boot_cpu_data.hlt_works_ok) {
  93                 printk("disabled\n");
  94                 return;
  95         }
  96         halt();
  97         halt();
  98         halt();
  99         halt();
 100         printk("OK.\n");
 101 }
 102
 103 /*
 104  *      Most 386 processors have a bug where a POPAD can lock the
 105  *      machine even from user space.
 106  */
 107
 108 static void __init check_popad(void)
 109 {
 110 #ifndef CONFIG_X86_POPAD_OK
 111         int res, inp = (int) &res;
 112
 113         printk(KERN_INFO "Checking for popad bug... ");
 114         __asm__ __volatile__(
 115           "movl $12345678,%%eax; movl $0,%%edi; pusha; popa; movl (%%edx,%%edi),%%ecx "
 116           : "=&a" (res)
 117           : "d" (inp)
 118           : "ecx", "edi" );
 119         /* If this fails, it means that any user program may lock the CPU hard. Too bad. */
 120         if (res != 12345678) printk( "Buggy.\n" );
 121                         else printk( "OK.\n" );
 122 #endif
 123 }
 124
 125 /*
 126  * Check whether we are able to run this kernel safely on SMP.
 127  *
 128  * - In order to run on a i386, we need to be compiled for i386
 129  *   (for due to lack of "invlpg" and working WP on a i386)
 130  * - In order to run on anything without a TSC, we need to be
 131  *   compiled for a i486.
 132  * - In order to support the local APIC on a buggy Pentium machine,
 133  *   we need to be compiled with CONFIG_X86_GOOD_APIC disabled,
 134  *   which happens implicitly if compiled for a Pentium or lower
 135  *   (unless an advanced selection of CPU features is used) as an
 136  *   otherwise config implies a properly working local APIC without
 137  *   the need to do extra reads from the APIC.
 138 */
 139
 140 static void __init check_config(void)
 141 {
 142 /*
 143  * We'd better not be a i386 if we're configured to use some
 144  * i486+ only features! (WP works in supervisor mode and the
 145  * new "invlpg" and "bswap" instructions)
 146  */
 147 #if defined(CONFIG_X86_WP_WORKS_OK) || defined(CONFIG_X86_INVLPG) || defined(CONFIG_X86_BSWAP)
 148         if (boot_cpu_data.x86 == 3)
 149                 panic("Kernel requires i486+ for 'invlpg' and other features");
 150 #endif
 151
 152 /*
 153  * If we configured ourselves for a TSC, we'd better have one!
 154  */
 155 #ifdef CONFIG_X86_TSC
 156         if (!cpu_has_tsc && !tsc_disable)
 157                 panic("Kernel compiled for Pentium+, requires TSC feature!");
 158 #endif
 159
 160 /*
 161  * If we were told we had a good local APIC, check for buggy Pentia,
 162  * i.e. all B steppings and the C2 stepping of P54C when using their
 163  * integrated APIC (see 11AP erratum in "Pentium Processor
 164  * Specification Update").
 165  */
 166 #if defined(CONFIG_X86_LOCAL_APIC) && defined(CONFIG_X86_GOOD_APIC)
 167         if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL
 168             && cpu_has_apic
 169             && boot_cpu_data.x86 == 5
 170             && boot_cpu_data.x86_model == 2
 171             && (boot_cpu_data.x86_mask < 6 || boot_cpu_data.x86_mask == 11))
 172                 panic("Kernel compiled for PMMX+, assumes a local APIC without the read-before-write bug!");
 173 #endif
 174 }
 175
 176
 177 void __init check_bugs(void)
 178 {
 179         identify_boot_cpu();
 180 #ifndef CONFIG_SMP
 181         printk("CPU: ");
 182         print_cpu_info(&boot_cpu_data);
 183 #endif
 184         check_config();
 185         check_fpu();
 186         check_hlt();
 187         check_popad();
 188         init_utsname()->machine[1] = '0' + (boot_cpu_data.x86 > 6 ? 6 : boot_cpu_data.x86);
 189         alternative_instructions();
 190 }