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    Subject[PATCH 147/208] x86/fpu: Optimize fpu_copy()
    Date
    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@alien8.de>
    Cc: Andy Lutomirski <luto@amacapital.net>
    Cc: Dave Hansen <dave.hansen@linux.intel.com>
    Cc: Fenghua Yu <fenghua.yu@intel.com>
    Cc: H. Peter Anvin <hpa@zytor.com>
    Cc: Linus Torvalds <torvalds@linux-foundation.org>
    Cc: Oleg Nesterov <oleg@redhat.com>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Signed-off-by: Ingo Molnar <mingo@kernel.org>
    ---
    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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