diff options
author | Sebastian Andrzej Siewior <bigeasy@linutronix.de> | 2018-11-29 16:02:10 +0100 |
---|---|---|
committer | Borislav Petkov <bp@suse.de> | 2018-12-04 12:37:28 +0100 |
commit | 12209993e98c5fa1855c467f22a24e3d5b8be205 (patch) | |
tree | 73e4a7b5e6e48b1562b8db90523ade974db242cd /arch/x86/include/asm/fpu | |
parent | 2f2fcc40a961ed04f0e130803fbaa868c2899310 (diff) | |
download | linux-stable-12209993e98c5fa1855c467f22a24e3d5b8be205.tar.gz linux-stable-12209993e98c5fa1855c467f22a24e3d5b8be205.tar.bz2 linux-stable-12209993e98c5fa1855c467f22a24e3d5b8be205.zip |
x86/fpu: Don't export __kernel_fpu_{begin,end}()
There is one user of __kernel_fpu_begin() and before invoking it,
it invokes preempt_disable(). So it could invoke kernel_fpu_begin()
right away. The 32bit version of arch_efi_call_virt_setup() and
arch_efi_call_virt_teardown() does this already.
The comment above *kernel_fpu*() claims that before invoking
__kernel_fpu_begin() preemption should be disabled and that KVM is a
good example of doing it. Well, KVM doesn't do that since commit
f775b13eedee2 ("x86,kvm: move qemu/guest FPU switching out to vcpu_run")
so it is not an example anymore.
With EFI gone as the last user of __kernel_fpu_{begin|end}(), both can
be made static and not exported anymore.
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Rik van Riel <riel@surriel.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: "Jason A. Donenfeld" <Jason@zx2c4.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Nicolai Stange <nstange@suse.de>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: kvm ML <kvm@vger.kernel.org>
Cc: linux-efi <linux-efi@vger.kernel.org>
Cc: x86-ml <x86@kernel.org>
Link: https://lkml.kernel.org/r/20181129150210.2k4mawt37ow6c2vq@linutronix.de
Diffstat (limited to 'arch/x86/include/asm/fpu')
-rw-r--r-- | arch/x86/include/asm/fpu/api.h | 15 |
1 files changed, 5 insertions, 10 deletions
diff --git a/arch/x86/include/asm/fpu/api.h b/arch/x86/include/asm/fpu/api.h index a9caac9d4a72..b56d504af654 100644 --- a/arch/x86/include/asm/fpu/api.h +++ b/arch/x86/include/asm/fpu/api.h @@ -12,17 +12,12 @@ #define _ASM_X86_FPU_API_H /* - * Careful: __kernel_fpu_begin/end() must be called with preempt disabled - * and they don't touch the preempt state on their own. - * If you enable preemption after __kernel_fpu_begin(), preempt notifier - * should call the __kernel_fpu_end() to prevent the kernel/user FPU - * state from getting corrupted. KVM for example uses this model. - * - * All other cases use kernel_fpu_begin/end() which disable preemption - * during kernel FPU usage. + * Use kernel_fpu_begin/end() if you intend to use FPU in kernel context. It + * disables preemption so be careful if you intend to use it for long periods + * of time. + * If you intend to use the FPU in softirq you need to check first with + * irq_fpu_usable() if it is possible. */ -extern void __kernel_fpu_begin(void); -extern void __kernel_fpu_end(void); extern void kernel_fpu_begin(void); extern void kernel_fpu_end(void); extern bool irq_fpu_usable(void); |