diff options
| author | Andy Lutomirski <luto@kernel.org> | 2021-01-21 08:09:51 +0300 |
|---|---|---|
| committer | Borislav Petkov <bp@suse.de> | 2021-01-29 14:27:47 +0300 |
| commit | 49200d17d27d5cc1aede2d1bb2a78dbfc1563e65 (patch) | |
| tree | 8f126191de040ce89b2800b4e4204fad8d666a64 /arch/x86/include/asm | |
| parent | b0dc553cfc9d3bc2c7b8672b0b2fcf0edf0c3b6e (diff) | |
| download | linux-49200d17d27d5cc1aede2d1bb2a78dbfc1563e65.tar.xz | |
x86/fpu/64: Don't FNINIT in kernel_fpu_begin()
The remaining callers of kernel_fpu_begin() in 64-bit kernels don't use 387
instructions, so there's no need to sanitize the FPU state. Skip it to get
most of the performance we lost back.
Reported-by: Krzysztof Olędzki <ole@ans.pl>
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/57f8841ccbf9f3c25a23196c888f5f6ec5887577.1611205691.git.luto@kernel.org
Diffstat (limited to 'arch/x86/include/asm')
| -rw-r--r-- | arch/x86/include/asm/fpu/api.h | 12 |
1 files changed, 12 insertions, 0 deletions
diff --git a/arch/x86/include/asm/fpu/api.h b/arch/x86/include/asm/fpu/api.h index 67a4f1cb2aac..ed33a14188f6 100644 --- a/arch/x86/include/asm/fpu/api.h +++ b/arch/x86/include/asm/fpu/api.h @@ -32,7 +32,19 @@ extern void fpregs_mark_activate(void); /* Code that is unaware of kernel_fpu_begin_mask() can use this */ static inline void kernel_fpu_begin(void) { +#ifdef CONFIG_X86_64 + /* + * Any 64-bit code that uses 387 instructions must explicitly request + * KFPU_387. + */ + kernel_fpu_begin_mask(KFPU_MXCSR); +#else + /* + * 32-bit kernel code may use 387 operations as well as SSE2, etc, + * as long as it checks that the CPU has the required capability. + */ kernel_fpu_begin_mask(KFPU_387 | KFPU_MXCSR); +#endif } /* |