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