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

The preempt_disable() section was introduced in commit

  a10b6a16cdad8 ("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 <[email protected]>
Signed-off-by: Borislav Petkov <[email protected]>
Reviewed-by: Borislav Petkov <[email protected]>
Reviewed-by: Dave Hansen <[email protected]>
Reviewed-by: Thomas Gleixner <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: "Jason A. Donenfeld" <[email protected]>
Cc: kvm ML <[email protected]>
Cc: Nicolai Stange <[email protected]>
Cc: Paolo Bonzini <[email protected]>
Cc: Radim Krčmář <[email protected]>
Cc: Rik van Riel <[email protected]>
Cc: x86-ml <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]

1 files changed, 0 insertions, 2 deletions

diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c
index 1d3ae7988f7f..1940319268ae 100644
--- a/arch/x86/kernel/fpu/core.c
+++ b/arch/x86/kernel/fpu/core.c
@@ -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();
 	}
 }