1b2441318SGreg Kroah-Hartman // SPDX-License-Identifier: GPL-2.0 20bf23f3dSIngo Molnar /* 30bf23f3dSIngo Molnar * x86 FPU bug checks: 40bf23f3dSIngo Molnar */ 5*b56d2795SThomas Gleixner #include <asm/fpu/api.h> 60bf23f3dSIngo Molnar 70bf23f3dSIngo Molnar /* 80bf23f3dSIngo Molnar * Boot time CPU/FPU FDIV bug detection code: 90bf23f3dSIngo Molnar */ 100bf23f3dSIngo Molnar 110bf23f3dSIngo Molnar static double __initdata x = 4195835.0; 120bf23f3dSIngo Molnar static double __initdata y = 3145727.0; 130bf23f3dSIngo Molnar 140bf23f3dSIngo Molnar /* 150bf23f3dSIngo Molnar * This used to check for exceptions.. 160bf23f3dSIngo Molnar * However, it turns out that to support that, 170bf23f3dSIngo Molnar * the XMM trap handlers basically had to 180bf23f3dSIngo Molnar * be buggy. So let's have a correct XMM trap 190bf23f3dSIngo Molnar * handler, and forget about printing out 200bf23f3dSIngo Molnar * some status at boot. 210bf23f3dSIngo Molnar * 220bf23f3dSIngo Molnar * We should really only care about bugs here 230bf23f3dSIngo Molnar * anyway. Not features. 240bf23f3dSIngo Molnar */ fpu__init_check_bugs(void)25de82fbc3SBorislav Petkovvoid __init fpu__init_check_bugs(void) 260bf23f3dSIngo Molnar { 270bf23f3dSIngo Molnar s32 fdiv_bug; 280bf23f3dSIngo Molnar 29de82fbc3SBorislav Petkov /* kernel_fpu_begin/end() relies on patched alternative instructions. */ 30de82fbc3SBorislav Petkov if (!boot_cpu_has(X86_FEATURE_FPU)) 31de82fbc3SBorislav Petkov return; 32de82fbc3SBorislav Petkov 330bf23f3dSIngo Molnar kernel_fpu_begin(); 340bf23f3dSIngo Molnar 350bf23f3dSIngo Molnar /* 360bf23f3dSIngo Molnar * trap_init() enabled FXSR and company _before_ testing for FP 370bf23f3dSIngo Molnar * problems here. 380bf23f3dSIngo Molnar * 390bf23f3dSIngo Molnar * Test for the divl bug: http://en.wikipedia.org/wiki/Fdiv_bug 400bf23f3dSIngo Molnar */ 410bf23f3dSIngo Molnar __asm__("fninit\n\t" 420bf23f3dSIngo Molnar "fldl %1\n\t" 430bf23f3dSIngo Molnar "fdivl %2\n\t" 440bf23f3dSIngo Molnar "fmull %2\n\t" 450bf23f3dSIngo Molnar "fldl %1\n\t" 460bf23f3dSIngo Molnar "fsubp %%st,%%st(1)\n\t" 470bf23f3dSIngo Molnar "fistpl %0\n\t" 480bf23f3dSIngo Molnar "fwait\n\t" 490bf23f3dSIngo Molnar "fninit" 500bf23f3dSIngo Molnar : "=m" (*&fdiv_bug) 510bf23f3dSIngo Molnar : "m" (*&x), "m" (*&y)); 520bf23f3dSIngo Molnar 530bf23f3dSIngo Molnar kernel_fpu_end(); 540bf23f3dSIngo Molnar 550bf23f3dSIngo Molnar if (fdiv_bug) { 560bf23f3dSIngo Molnar set_cpu_bug(&boot_cpu_data, X86_BUG_FDIV); 570bf23f3dSIngo Molnar pr_warn("Hmm, FPU with FDIV bug\n"); 580bf23f3dSIngo Molnar } 590bf23f3dSIngo Molnar } 60