x86/fpu: Remove preempt_disable() in fpu__clear()

The preempt_disable() section was introduced in commit

  a10b6a16cd ("x86/fpu: Make the fpu state change in fpu__clear() scheduler-atomic")

and it was said to be temporary.

fpu__initialize() initializes the FPU struct to its initial value and
then sets ->initialized to 1. The last part is the important one.
The content of the state does not matter because it gets set via
copy_init_fpstate_to_fpregs().

A preemption here has little meaning because the registers will always be
set to the same content after copy_init_fpstate_to_fpregs(). A softirq
with a kernel_fpu_begin() could also force to save FPU's registers after
fpu__initialize() without changing the outcome here.

Remove the preempt_disable() section in fpu__clear(), preemption here
does not hurt.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Dave Hansen <dave.hansen@intel.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "Jason A. Donenfeld" <Jason@zx2c4.com>
Cc: kvm ML <kvm@vger.kernel.org>
Cc: Nicolai Stange <nstange@suse.de>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: x86-ml <x86@kernel.org>
Link: https://lkml.kernel.org/r/20190403164156.19645-4-bigeasy@linutronix.de
This commit is contained in:
Sebastian Andrzej Siewior 2019-04-03 18:41:32 +02:00 committed by Borislav Petkov
parent 6dd677a044
commit 60e528d6ce
1 changed files with 0 additions and 2 deletions

View File

@ -366,11 +366,9 @@ void fpu__clear(struct fpu *fpu)
* Make sure fpstate is cleared and initialized.
*/
if (static_cpu_has(X86_FEATURE_FPU)) {
preempt_disable();
fpu__initialize(fpu);
user_fpu_begin();
copy_init_fpstate_to_fpregs();
preempt_enable();
}
}