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_387(char *s) 21 { 22 boot_cpu_data.hard_math = 0; 23 write_cr0(X86_CR0_TS | X86_CR0_EM | X86_CR0_MP | read_cr0()); 24 return 1; 25 } 26 27 __setup("no387", no_387); 28 29 static double __initdata x = 4195835.0; 30 static double __initdata y = 3145727.0; 31 32 /* 33 * This used to check for exceptions.. 34 * However, it turns out that to support that, 35 * the XMM trap handlers basically had to 36 * be buggy. So let's have a correct XMM trap 37 * handler, and forget about printing out 38 * some status at boot. 39 * 40 * We should really only care about bugs here 41 * anyway. Not features. 42 */ 43 static void __init check_fpu(void) 44 { 45 s32 fdiv_bug; 46 47 if (!boot_cpu_data.hard_math) { 48 #ifndef CONFIG_MATH_EMULATION 49 pr_emerg("No coprocessor found and no math emulation present\n"); 50 pr_emerg("Giving up\n"); 51 for (;;) ; 52 #endif 53 return; 54 } 55 56 kernel_fpu_begin(); 57 58 /* 59 * trap_init() enabled FXSR and company _before_ testing for FP 60 * problems here. 61 * 62 * Test for the divl bug: http://en.wikipedia.org/wiki/Fdiv_bug 63 */ 64 __asm__("fninit\n\t" 65 "fldl %1\n\t" 66 "fdivl %2\n\t" 67 "fmull %2\n\t" 68 "fldl %1\n\t" 69 "fsubp %%st,%%st(1)\n\t" 70 "fistpl %0\n\t" 71 "fwait\n\t" 72 "fninit" 73 : "=m" (*&fdiv_bug) 74 : "m" (*&x), "m" (*&y)); 75 76 kernel_fpu_end(); 77 78 if (fdiv_bug) { 79 set_cpu_bug(&boot_cpu_data, X86_BUG_FDIV); 80 pr_warn("Hmm, FPU with FDIV bug\n"); 81 } 82 } 83 84 void __init check_bugs(void) 85 { 86 identify_boot_cpu(); 87 #ifndef CONFIG_SMP 88 pr_info("CPU: "); 89 print_cpu_info(&boot_cpu_data); 90 #endif 91 92 /* 93 * Check whether we are able to run this kernel safely on SMP. 94 * 95 * - i386 is no longer supported. 96 * - In order to run on anything without a TSC, we need to be 97 * compiled for a i486. 98 */ 99 if (boot_cpu_data.x86 < 4) 100 panic("Kernel requires i486+ for 'invlpg' and other features"); 101 102 init_utsname()->machine[1] = 103 '0' + (boot_cpu_data.x86 > 6 ? 6 : boot_cpu_data.x86); 104 alternative_instructions(); 105 106 /* 107 * kernel_fpu_begin/end() in check_fpu() relies on the patched 108 * alternative instructions. 109 */ 110 check_fpu(); 111 } 112