linux-kernel - Re: [PATCH -next v4 04/19] arm64: entry: Remove __enter_from_kernel

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Message-ID: <ZyDzNmSgmYkXWcdD@J2N7QTR9R3.cambridge.arm.com>
Date: Tue, 29 Oct 2024 14:37:42 +0000
From: Mark Rutland <mark.rutland@....com>
To: Jinjie Ruan <ruanjinjie@...wei.com>
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Subject: Re: [PATCH -next v4 04/19] arm64: entry: Remove
 __enter_from_kernel_mode()

On Fri, Oct 25, 2024 at 06:06:45PM +0800, Jinjie Ruan wrote:
> The __enter_from_kernel_mode() is only called by enter_from_kernel_mode(),
> remove it.

The point of this split is to cleanly separate the raw entry logic (in
__enter_from_kernel_mode() from pieces that run later and can safely be
instrumented (later in enter_from_kernel_mode()).

I had expected that a later patch would replace
__enter_from_kernel_mode() with the generic equivalent, leaving
enter_from_kernel_mode() unchanged. It looks like patch 16 could do that
without this patch being necessary -- am I missing something?

Mark.

> 
> No functional changes.
> 
> Signed-off-by: Jinjie Ruan <ruanjinjie@...wei.com>
> ---
>  arch/arm64/kernel/entry-common.c | 9 +--------
>  1 file changed, 1 insertion(+), 8 deletions(-)
> 
> diff --git a/arch/arm64/kernel/entry-common.c b/arch/arm64/kernel/entry-common.c
> index ccf59b44464d..a7fd4d6c7650 100644
> --- a/arch/arm64/kernel/entry-common.c
> +++ b/arch/arm64/kernel/entry-common.c
> @@ -36,7 +36,7 @@
>   * This is intended to match the logic in irqentry_enter(), handling the kernel
>   * mode transitions only.
>   */
> -static __always_inline irqentry_state_t __enter_from_kernel_mode(struct pt_regs *regs)
> +static noinstr irqentry_state_t enter_from_kernel_mode(struct pt_regs *regs)
>  {
>  	irqentry_state_t ret = {
>  		.exit_rcu = false,
> @@ -55,13 +55,6 @@ static __always_inline irqentry_state_t __enter_from_kernel_mode(struct pt_regs
>  	rcu_irq_enter_check_tick();
>  	trace_hardirqs_off_finish();
>  
> -	return ret;
> -}
> -
> -static noinstr irqentry_state_t enter_from_kernel_mode(struct pt_regs *regs)
> -{
> -	irqentry_state_t ret = __enter_from_kernel_mode(regs);
> -
>  	mte_check_tfsr_entry();
>  	mte_disable_tco_entry(current);
>  
> -- 
> 2.34.1
>