Andy Lutomirski f5ee8afc19 x86/fpu: Add kernel_fpu_begin_mask() to selectively initialize state ... commit e45122893a upstream. Currently, requesting kernel FPU access doesn't distinguish which parts of the extended ("FPU") state are needed. This is nice for simplicity, but there are a few cases in which it's suboptimal: - The vast majority of in-kernel FPU users want XMM/YMM/ZMM state but do not use legacy 387 state. These users want MXCSR initialized but don't care about the FPU control word. Skipping FNINIT would save time. (Empirically, FNINIT is several times slower than LDMXCSR.) - Code that wants MMX doesn't want or need MXCSR initialized. _mmx_memcpy(), for example, can run before CR4.OSFXSR gets set, and initializing MXCSR will fail because LDMXCSR generates an #UD when the aforementioned CR4 bit is not set. - Any future in-kernel users of XFD (eXtended Feature Disable)-capable dynamic states will need special handling. Add a more specific API that allows callers to specify exactly what they want. Signed-off-by: Andy Lutomirski <luto@kernel.org> Signed-off-by: Borislav Petkov <bp@suse.de> Tested-by: Krzysztof Piotr Olędzki <ole@ans.pl> Link: https://lkml.kernel.org/r/aff1cac8b8fc7ee900cf73e8f2369966621b053f.1611205691.git.luto@kernel.org Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>		2021-01-27 11:55:13 +01:00
..
bugs.c	License cleanup: add SPDX GPL-2.0 license identifier to files with no license	2017-11-02 11:10:55 +01:00
core.c	x86/fpu: Add kernel_fpu_begin_mask() to selectively initialize state	2021-01-27 11:55:13 +01:00
init.c	x86/fpu: Handle FPU-related and clearcpuid command line arguments earlier	2020-09-22 00:24:27 +02:00
Makefile	treewide: Add SPDX license identifier - Makefile/Kconfig	2019-05-21 10:50:46 +02:00
regset.c	x86: switch to ->regset_get()	2020-07-27 14:31:07 -04:00
signal.c	x86: switch to ->regset_get()	2020-07-27 14:31:07 -04:00
xstate.c	x86/mmu: Allocate/free a PASID	2020-09-17 20:22:15 +02:00