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/processor-flags.h>
  15 #include <asm/i387.h>
  16 #include <asm/msr.h>
  17 #include <asm/paravirt.h>
  18 #include <asm/alternative.h>
  19
  20 static int __init no_halt(char *s)
  21 {
  22         boot_cpu_data.hlt_works_ok = 0;
  23         return 1;
  24 }
  25
  26 __setup("no-hlt", no_halt);
  27
  28 static int __init mca_pentium(char *s)
  29 {
  30         mca_pentium_flag = 1;
  31         return 1;
  32 }
  33
  34 __setup("mca-pentium", mca_pentium);
  35
  36 static int __init no_387(char *s)
  37 {
  38         boot_cpu_data.hard_math = 0;
  39         write_cr0(X86_CR0_TS | X86_CR0_EM | X86_CR0_MP | read_cr0());
  40         return 1;
  41 }
  42
  43 __setup("no387", no_387);
  44
  45 static double __initdata x = 4195835.0;
  46 static double __initdata y = 3145727.0;
  47
  48 /*
  49  * This used to check for exceptions..
  50  * However, it turns out that to support that,
  51  * the XMM trap handlers basically had to
  52  * be buggy. So let's have a correct XMM trap
  53  * handler, and forget about printing out
  54  * some status at boot.
  55  *
  56  * We should really only care about bugs here
  57  * anyway. Not features.
  58  */
  59 static void __init check_fpu(void)
  60 {
  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");
  65                 for (;;) ;
  66 #endif
  67                 return;
  68         }
  69
  70 /* trap_init() enabled FXSR and company _before_ testing for FP problems here. */
  71         /* Test for the divl bug.. */
  72         __asm__("fninit\n\t"
  73                 "fldl %1\n\t"
  74                 "fdivl %2\n\t"
  75                 "fmull %2\n\t"
  76                 "fldl %1\n\t"
  77                 "fsubp %%st,%%st(1)\n\t"
  78                 "fistpl %0\n\t"
  79                 "fwait\n\t"
  80                 "fninit"
  81                 : "=m" (*&boot_cpu_data.fdiv_bug)
  82                 : "m" (*&x), "m" (*&y));
  83         if (boot_cpu_data.fdiv_bug)
  84                 printk("Hmm, FPU with FDIV bug.\n");
  85 }
  86
  87 static void __init check_hlt(void)
  88 {
  89         if (paravirt_enabled())
  90                 return;
  91
  92         printk(KERN_INFO "Checking 'hlt' instruction... ");
  93         if (!boot_cpu_data.hlt_works_ok) {
  94                 printk("disabled\n");
  95                 return;
  96         }
  97         halt();
  98         halt();
  99         halt();
 100         halt();
 101         printk("OK.\n");
 102 }
 103
 104 /*
 105  *      Most 386 processors have a bug where a POPAD can lock the
 106  *      machine even from user space.
 107  */
 108
 109 static void __init check_popad(void)
 110 {
 111 #ifndef CONFIG_X86_POPAD_OK
 112         int res, inp = (int) &res;
 113
 114         printk(KERN_INFO "Checking for popad bug... ");
 115         __asm__ __volatile__(
 116           "movl $12345678,%%eax; movl $0,%%edi; pusha; popa; movl (%%edx,%%edi),%%ecx "
 117           : "=&a" (res)
 118           : "d" (inp)
 119           : "ecx", "edi" );
 120         /* If this fails, it means that any user program may lock the CPU hard. Too bad. */
 121         if (res != 12345678) printk( "Buggy.\n" );
 122                         else printk( "OK.\n" );
 123 #endif
 124 }
 125
 126 /*
 127  * Check whether we are able to run this kernel safely on SMP.
 128  *
 129  * - In order to run on a i386, we need to be compiled for i386
 130  *   (for due to lack of "invlpg" and working WP on a i386)
 131  * - In order to run on anything without a TSC, we need to be
 132  *   compiled for a i486.
 133  * - In order to support the local APIC on a buggy Pentium machine,
 134  *   we need to be compiled with CONFIG_X86_GOOD_APIC disabled,
 135  *   which happens implicitly if compiled for a Pentium or lower
 136  *   (unless an advanced selection of CPU features is used) as an
 137  *   otherwise config implies a properly working local APIC without
 138  *   the need to do extra reads from the APIC.
 139 */
 140
 141 static void __init check_config(void)
 142 {
 143 /*
 144  * We'd better not be a i386 if we're configured to use some
 145  * i486+ only features! (WP works in supervisor mode and the
 146  * new "invlpg" and "bswap" instructions)
 147  */
 148 #if defined(CONFIG_X86_WP_WORKS_OK) || defined(CONFIG_X86_INVLPG) || defined(CONFIG_X86_BSWAP)
 149         if (boot_cpu_data.x86 == 3)
 150                 panic("Kernel requires i486+ for 'invlpg' and other features");
 151 #endif
 152
 153 /*
 154  * If we configured ourselves for a TSC, we'd better have one!
 155  */
 156 #ifdef CONFIG_X86_TSC
 157         if (!cpu_has_tsc)
 158                 panic("Kernel compiled for Pentium+, requires TSC feature!");
 159 #endif
 160
 161 /*
 162  * If we were told we had a good local APIC, check for buggy Pentia,
 163  * i.e. all B steppings and the C2 stepping of P54C when using their
 164  * integrated APIC (see 11AP erratum in "Pentium Processor
 165  * Specification Update").
 166  */
 167 #if defined(CONFIG_X86_LOCAL_APIC) && defined(CONFIG_X86_GOOD_APIC)
 168         if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL
 169             && cpu_has_apic
 170             && boot_cpu_data.x86 == 5
 171             && boot_cpu_data.x86_model == 2
 172             && (boot_cpu_data.x86_mask < 6 || boot_cpu_data.x86_mask == 11))
 173                 panic("Kernel compiled for PMMX+, assumes a local APIC without the read-before-write bug!");
 174 #endif
 175 }
 176
 177
 178 void __init check_bugs(void)
 179 {
 180         identify_boot_cpu();
 181 #ifndef CONFIG_SMP
 182         printk("CPU: ");
 183         print_cpu_info(&boot_cpu_data);
 184 #endif
 185         check_config();
 186         check_fpu();
 187         check_hlt();
 188         check_popad();
 189         init_utsname()->machine[1] = '0' + (boot_cpu_data.x86 > 6 ? 6 : boot_cpu_data.x86);
 190         alternative_instructions();
 191 }