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Date:   Wed,  9 Jan 2019 12:47:28 +0100
From:   Sebastian Andrzej Siewior <>
Cc:, Andy Lutomirski <>,
        Paolo Bonzini <>,
        Radim Krčmář <>,, "Jason A. Donenfeld" <>,
        Rik van Riel <>,
        Dave Hansen <>,
        Sebastian Andrzej Siewior <>
Subject: [PATCH 06/22] x86/fpu: Don't save fxregs for ia32 frames in copy_fpstate_to_sigframe()

Why does copy_fpstate_to_sigframe() do copy_fxregs_to_kernel() in the
ia32_fxstate case? I don't know. It just does.
Maybe it was required at some point, maybe it was added by accident and
nobody noticed it because it makes no difference.

In copy_fpstate_to_sigframe() we stash the FPU state into the task's
stackframe. Then the CPU's FPU registers (and its fpu->state) are
cleared (handle_signal() does fpu__clear()). So it makes *no* difference
what happens to fpu->state after copy_fpregs_to_sigframe().

Remove copy_fxregs_to_kernel() since it does not matter what it does and
save a few cycles.

Signed-off-by: Sebastian Andrzej Siewior <>
 arch/x86/kernel/fpu/signal.c | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/arch/x86/kernel/fpu/signal.c b/arch/x86/kernel/fpu/signal.c
index c136a4327659d..047390a45e016 100644
--- a/arch/x86/kernel/fpu/signal.c
+++ b/arch/x86/kernel/fpu/signal.c
@@ -174,9 +174,6 @@ int copy_fpstate_to_sigframe(void __user *buf, void __user *buf_fx, int size)
 	/* Save the live register state to the user directly. */
 	if (copy_fpregs_to_sigframe(buf_fx))
 		return -1;
-	/* Update the thread's fxstate to save the fsave header. */
-	if (ia32_fxstate)
-		copy_fxregs_to_kernel(fpu);
 	/* Save the fsave header for the 32-bit frames. */
 	if ((ia32_fxstate || !use_fxsr()) && save_fsave_header(tsk, buf))

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