projects / linux-block.git / blame
| Commit | Line | Data |
|---|---|---|
| b2441318 | 1 | // SPDX-License-Identifier: GPL-2.0 |
| 0bf23f3d IM |
2 | /* |
| 3 | * x86 FPU bug checks: | |
| 4 | */ | |
| 5 | #include <asm/fpu/internal.h> | |
| 6 | ||
| 7 | /* | |
| 8 | * Boot time CPU/FPU FDIV bug detection code: | |
| 9 | */ | |
| 10 | ||
| 11 | static double __initdata x = 4195835.0; | |
| 12 | static double __initdata y = 3145727.0; | |
| 13 | ||
| 14 | /* | |
| 15 | * This used to check for exceptions.. | |
| 16 | * However, it turns out that to support that, | |
| 17 | * the XMM trap handlers basically had to | |
| 18 | * be buggy. So let's have a correct XMM trap | |
| 19 | * handler, and forget about printing out | |
| 20 | * some status at boot. | |
| 21 | * | |
| 22 | * We should really only care about bugs here | |
| 23 | * anyway. Not features. | |
| 24 | */ | |
| de82fbc3 | 25 | void __init fpu__init_check_bugs(void) |
| 0bf23f3d IM |
26 | { |
| 27 | s32 fdiv_bug; | |
| 28 | ||
| de82fbc3 BP |
29 | /* kernel_fpu_begin/end() relies on patched alternative instructions. */ |
| 30 | if (!boot_cpu_has(X86_FEATURE_FPU)) | |
| 31 | return; | |
| 32 | ||
| 0bf23f3d IM |
33 | kernel_fpu_begin(); |
| 34 | ||
| 35 | /* | |
| 36 | * trap_init() enabled FXSR and company _before_ testing for FP | |
| 37 | * problems here. | |
| 38 | * | |
| 39 | * Test for the divl bug: http://en.wikipedia.org/wiki/Fdiv_bug | |
| 40 | */ | |
| 41 | __asm__("fninit\n\t" | |
| 42 | "fldl %1\n\t" | |
| 43 | "fdivl %2\n\t" | |
| 44 | "fmull %2\n\t" | |
| 45 | "fldl %1\n\t" | |
| 46 | "fsubp %%st,%%st(1)\n\t" | |
| 47 | "fistpl %0\n\t" | |
| 48 | "fwait\n\t" | |
| 49 | "fninit" | |
| 50 | : "=m" (*&fdiv_bug) | |
| 51 | : "m" (*&x), "m" (*&y)); | |
| 52 | ||
| 53 | kernel_fpu_end(); | |
| 54 | ||
| 55 | if (fdiv_bug) { | |
| 56 | set_cpu_bug(&boot_cpu_data, X86_BUG_FDIV); | |
| 57 | pr_warn("Hmm, FPU with FDIV bug\n"); | |
| 58 | } | |
| 59 | } |