[PATCH 147/208] x86/fpu: Optimize fpu_copy()

[Ingo Molnar]

Optimize fpu_copy() a bit by expanding the ->fpstate_active == 1
portion of fpu__save() into it.

( The main purpose of this change is to enable another, larger
  optimization that will be done in the next patch. )

Reviewed-by: Borislav Petkov <bp@xxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Cc: Fenghua Yu <fenghua.yu@xxxxxxxxx>
Cc: H. Peter Anvin <hpa@xxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
 arch/x86/kernel/fpu/core.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c
index 8835b802aa16..7fdeabc1f2af 100644
--- a/arch/x86/kernel/fpu/core.c
+++ b/arch/x86/kernel/fpu/core.c
@@ -224,7 +224,10 @@ static void fpu_copy(struct fpu *dst_fpu, struct fpu *src_fpu)
 		memset(&dst_fpu->state.xsave, 0, xstate_size);
 		copy_fpregs_to_fpstate(dst_fpu);
 	} else {
-		fpu__save(src_fpu);
+		preempt_disable();
+		if (!copy_fpregs_to_fpstate(src_fpu))
+			fpregs_deactivate(src_fpu);
+		preempt_enable();
 		memcpy(&dst_fpu->state, &src_fpu->state, xstate_size);
 	}
 }
-- 
2.1.0

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