Re: [PATCH 02/10] entry: Remove local_irq_{enable,disable}_exit_to_user()

[Jinjie Ruan]

On 2026/4/7 21:16, Mark Rutland wrote:
> The local_irq_enable_exit_to_user() and local_irq_disable_exit_to_user()
> functions are never overridden by architecture code, and are always
> equivalent to local_irq_enable() and local_irq_disable().
> 
> These functions were added on the assumption that arm64 would override
> them to manage 'DAIF' exception masking, as described by Thomas Gleixner
> in these threads:
> 
>   https://lore.kernel.org/all/20190919150809.340471236@xxxxxxxxxxxxx/
>   https://lore.kernel.org/all/alpine.DEB.2.21.1910240119090.1852@xxxxxxxxxxxxxxxxxxxxxxx/
> 
> In practice arm64 did not need to override either. Prior to moving to
> the generic irqentry code, arm64's management of DAIF was reworked in
> commit:
> 
>   97d935faacde ("arm64: Unmask Debug + SError in do_notify_resume()")
> 
> Since that commit, arm64 only masks interrupts during the 'prepare' step
> when returning to user mode, and masks other DAIF exceptions later.
> Within arm64_exit_to_user_mode(), the arm64 entry code is as follows:
> 
> 	local_irq_disable();
> 	exit_to_user_mode_prepare_legacy(regs);
> 	local_daif_mask();
> 	mte_check_tfsr_exit();
> 	exit_to_user_mode();
> 
> Remove the unnecessary local_irq_enable_exit_to_user() and
> local_irq_disable_exit_to_user() functions.
> 
> Signed-off-by: Mark Rutland <mark.rutland@xxxxxxx>
> Cc: Andy Lutomirski <luto@xxxxxxxxxx>
> Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
> Cc: Jinjie Ruan <ruanjinjie@xxxxxxxxxx>
> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> Cc: Thomas Gleixner <tglx@xxxxxxxxxx>
> Cc: Vladimir Murzin <vladimir.murzin@xxxxxxx>
> Cc: Will Deacon <will@xxxxxxxxxx>
> ---
>  include/linux/entry-common.h     |  2 +-
>  include/linux/irq-entry-common.h | 31 -------------------------------
>  kernel/entry/common.c            |  4 ++--
>  3 files changed, 3 insertions(+), 34 deletions(-)

Reviewed-by: Jinjie Ruan <ruanjinjie@xxxxxxxxxx>

> 
> diff --git a/include/linux/entry-common.h b/include/linux/entry-common.h
> index f83ca0abf2cdb..dbaa153100f44 100644
> --- a/include/linux/entry-common.h
> +++ b/include/linux/entry-common.h
> @@ -321,7 +321,7 @@ static __always_inline void syscall_exit_to_user_mode(struct pt_regs *regs)
>  {
>  	instrumentation_begin();
>  	syscall_exit_to_user_mode_work(regs);
> -	local_irq_disable_exit_to_user();
> +	local_irq_disable();
>  	syscall_exit_to_user_mode_prepare(regs);
>  	instrumentation_end();
>  	exit_to_user_mode();
> diff --git a/include/linux/irq-entry-common.h b/include/linux/irq-entry-common.h
> index 3cf4d21168ba1..93b4b551f7ae4 100644
> --- a/include/linux/irq-entry-common.h
> +++ b/include/linux/irq-entry-common.h
> @@ -100,37 +100,6 @@ static __always_inline void enter_from_user_mode(struct pt_regs *regs)
>  	instrumentation_end();
>  }
>  
> -/**
> - * local_irq_enable_exit_to_user - Exit to user variant of local_irq_enable()
> - * @ti_work:	Cached TIF flags gathered with interrupts disabled
> - *
> - * Defaults to local_irq_enable(). Can be supplied by architecture specific
> - * code.
> - */
> -static inline void local_irq_enable_exit_to_user(unsigned long ti_work);
> -
> -#ifndef local_irq_enable_exit_to_user
> -static __always_inline void local_irq_enable_exit_to_user(unsigned long ti_work)
> -{
> -	local_irq_enable();
> -}
> -#endif
> -
> -/**
> - * local_irq_disable_exit_to_user - Exit to user variant of local_irq_disable()
> - *
> - * Defaults to local_irq_disable(). Can be supplied by architecture specific
> - * code.
> - */
> -static inline void local_irq_disable_exit_to_user(void);
> -
> -#ifndef local_irq_disable_exit_to_user
> -static __always_inline void local_irq_disable_exit_to_user(void)
> -{
> -	local_irq_disable();
> -}
> -#endif
> -
>  /**
>   * arch_exit_to_user_mode_work - Architecture specific TIF work for exit
>   *				 to user mode.
> diff --git a/kernel/entry/common.c b/kernel/entry/common.c
> index 9ef63e4147913..b5e05d87ba391 100644
> --- a/kernel/entry/common.c
> +++ b/kernel/entry/common.c
> @@ -47,7 +47,7 @@ static __always_inline unsigned long __exit_to_user_mode_loop(struct pt_regs *re
>  	 */
>  	while (ti_work & EXIT_TO_USER_MODE_WORK_LOOP) {
>  
> -		local_irq_enable_exit_to_user(ti_work);
> +		local_irq_enable();
>  
>  		if (ti_work & (_TIF_NEED_RESCHED | _TIF_NEED_RESCHED_LAZY)) {
>  			if (!rseq_grant_slice_extension(ti_work & TIF_SLICE_EXT_DENY))
> @@ -74,7 +74,7 @@ static __always_inline unsigned long __exit_to_user_mode_loop(struct pt_regs *re
>  		 * might have changed while interrupts and preemption was
>  		 * enabled above.
>  		 */
> -		local_irq_disable_exit_to_user();
> +		local_irq_disable();
>  
>  		/* Check if any of the above work has queued a deferred wakeup */
>  		tick_nohz_user_enter_prepare();