Re: [PATCH 2/2] x86/entry: Inline enter_from_user_mode

[Andy Lutomirski <luto@amacapital.net>]

On May 30, 2016 5:30 AM, "Paolo Bonzini" <pbonzini@redhat.com> wrote:
>
> This matches what is already done for prepare_exit_to_usermode,
> and saves about 60 clock cycles (4% speedup) with the benchmark
> in the previous commit message.
>
> Cc: Andy Lutomirski <luto@kernel.org>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Rik van Riel <riel@redhat.com>
> Cc: H. Peter Anvin <hpa@zytor.com>
> Cc: Ingo Molnar <mingo@kernel.org.com>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
>  arch/x86/entry/common.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/x86/entry/common.c b/arch/x86/entry/common.c
> index 946bc1a..582bbc8 100644
> --- a/arch/x86/entry/common.c
> +++ b/arch/x86/entry/common.c
> @@ -40,7 +40,7 @@ static struct thread_info *pt_regs_to_thread_info(struct pt_regs *regs)
>
>  #ifdef CONFIG_CONTEXT_TRACKING
>  /* Called on entry from user mode with IRQs off. */
> -__visible void enter_from_user_mode(void)
> +__visible inline void enter_from_user_mode(void)
>  {
>         CT_WARN_ON(ct_state() != CONTEXT_USER);
>         __user_exit();

I wonder if an extern inline *declaration* is needed as well in this C
file.  At least C99 suggests it is.  Maybe __visible is sufficient to
force an external definition to be emitted.