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    Subject[PATCH 24/29] x86/fpu: Prepare copy_fpstate_to_sigframe() for TIF_NEED_FPU_LOAD
    Date
    From: Rik van Riel <riel@surriel.com>

    The FPU registers need only to be saved if TIF_NEED_FPU_LOAD is not set.
    Otherwise this has been already done and can be skipped.

    Signed-off-by: Rik van Riel <riel@surriel.com>
    Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
    ---
    arch/x86/kernel/fpu/signal.c | 11 ++++++++++-
    1 file changed, 10 insertions(+), 1 deletion(-)

    diff --git a/arch/x86/kernel/fpu/signal.c b/arch/x86/kernel/fpu/signal.c
    index d8c2242877040..6e516eeaea328 100644
    --- a/arch/x86/kernel/fpu/signal.c
    +++ b/arch/x86/kernel/fpu/signal.c
    @@ -156,7 +156,16 @@ int copy_fpstate_to_sigframe(void __user *buf, void __user *buf_fx, int size)
    sizeof(struct user_i387_ia32_struct), NULL,
    (struct _fpstate_32 __user *) buf) ? -1 : 1;

    - copy_fpregs_to_fpstate(fpu);
    + __fpregs_changes_begin();
    + /*
    + * If we do not need to load the FPU registers at return to userspace
    + * then the CPU has the current state and we need to save it. Otherwise
    + * it is already done and we can skip it.
    + */
    + if (!test_thread_flag(TIF_NEED_FPU_LOAD))
    + copy_fpregs_to_fpstate(fpu);
    +
    + __fpregs_changes_end();

    if (using_compacted_format()) {
    copy_xstate_to_user(buf_fx, xsave, 0, size);
    --
    2.20.0.rc1
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