Re: [PATCH RFC Dovetail 7.1] arm64: irq_pipeline: 7.1 specific adjustments

On Thu, 2026-06-11 at 15:40 +0200, Florian Bezdeka wrote:
> Signed-off-by: Florian Bezdeka <[email protected]>
> ---
> 
> Hi Philippe,
> 
> final tests are still running but the local tests are looking good.
> The EVL testsuite triggered a WARN_ONCE() - see process.c below - which
> caused the systems to hang.
> 
> Turned out the arm64 entry code got some refactorings that needed some
> adjustments - pipline wise.
> 
> I would fold the following into 7.1, so could you please double check?
> Thanks!
> 
>  arch/arm64/kernel/entry-common.c | 35 ++++++++++++++++++++++++++++----
>  arch/arm64/kernel/process.c      |  6 +++---
>  include/linux/irq-entry-common.h |  3 +++
>  3 files changed, 37 insertions(+), 7 deletions(-)
> 
> diff --git a/arch/arm64/kernel/entry-common.c b/arch/arm64/kernel/entry-common.c
> index b0e141266349..97f6d6904a5d 100644
> --- a/arch/arm64/kernel/entry-common.c
> +++ b/arch/arm64/kernel/entry-common.c
> @@ -166,7 +166,16 @@ static noinstr irqentry_state_t arm64_enter_from_kernel_mode(struct pt_regs *reg
>  static void noinstr arm64_exit_to_kernel_mode(struct pt_regs *regs,
>  					      irqentry_state_t state)
>  {
> -	local_irq_disable();
> +	if (irqs_pipelined()) {
> +		hard_local_irq_disable();
> +		if (running_inband()) {
> +			stall_inband_nocheck();
> +			trace_hardirqs_off();
> +		}
> +	} else {
> +		local_irq_disable();
> +	}
> +
>  	irqentry_exit_to_kernel_mode_preempt(regs, state);
>  	local_daif_mask();
>  	mte_check_tfsr_exit();
> @@ -175,7 +184,14 @@ static void noinstr arm64_exit_to_kernel_mode(struct pt_regs *regs,
>  
>  static __always_inline void arm64_syscall_enter_from_user_mode(struct pt_regs *regs)
>  {
> -	enter_from_user_mode(regs);
> +	if (running_inband()) {
> +		WARN_ON_ONCE(irq_pipeline_debug() && irqs_disabled());
> +		stall_inband_nocheck();
> +		enter_from_user_mode(regs);
> +		trace_hardirqs_on();
> +		unstall_inband_nocheck();
> +	}

Should enter_from_user_mode() be called while the inband stage is
stalled, or after unstalling? The exit part is called while being
stalled, so I kept that in sync, but I'm not 100% sure.

> +
>  	mte_disable_tco_entry(current);
>  	sme_enter_from_user_mode();
>  }
> @@ -191,6 +207,7 @@ static __always_inline void arm64_enter_from_user_mode(struct pt_regs *regs)
>  		WARN_ON_ONCE(irq_pipeline_debug() && irqs_disabled());
>  		stall_inband_nocheck();
>  		enter_from_user_mode(regs);
> +		rseq_note_user_irq_entry();
>  		trace_hardirqs_on();
>  		unstall_inband_nocheck();
>  	}
> @@ -226,8 +243,18 @@ static __always_inline void arm64_syscall_exit_to_user_mode(struct pt_regs *regs
>   */
>  static __always_inline void arm64_exit_to_user_mode(struct pt_regs *regs)
>  {
> -	local_irq_disable();
> -	irqentry_exit_to_user_mode_prepare(regs);
> +	if (irqs_pipelined()) {
> +		hard_local_irq_disable();
> +		if (running_inband()) {
> +			stall_inband_nocheck();
> +			trace_hardirqs_off();
> +			irqentry_exit_to_user_mode_prepare(regs);
> +		}
> +	} else {
> +		local_irq_disable();
> +		irqentry_exit_to_user_mode_prepare(regs);
> +	}
> +
>  	local_daif_mask();
>  	sme_exit_to_user_mode();
>  	mte_check_tfsr_exit();
> diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c
> index b1eac5fd75c1..0047d0bdedd9 100644
> --- a/arch/arm64/kernel/process.c
> +++ b/arch/arm64/kernel/process.c
> @@ -748,8 +748,8 @@ static inline void debug_switch_state(void)
>  		unsigned long pmr_expected = GIC_PRIO_IRQOFF;
>  		unsigned long pmr_actual = read_sysreg_s(SYS_ICC_PMR_EL1);
>  
> -		WARN_ONCE(daif_actual != daif_expected ||
> -			  pmr_actual != pmr_expected,
> +		WARN_ONCE(running_inband() && (daif_actual != daif_expected ||
> +			  pmr_actual != pmr_expected),
>  			  "Unexpected DAIF + PMR: 0x%lx + 0x%lx (expected 0x%lx + 0x%lx)\n",
>  			  daif_actual, pmr_actual,
>  			  daif_expected, pmr_expected);
> @@ -757,7 +757,7 @@ static inline void debug_switch_state(void)
>  		unsigned long daif_expected = DAIF_PROCCTX_NOIRQ;
>  		unsigned long daif_actual = read_sysreg(daif);
>  
> -		WARN_ONCE(daif_actual != daif_expected,
> +		WARN_ONCE(running_inband() && daif_actual != daif_expected,
>  			  "Unexpected DAIF value: 0x%lx (expected 0x%lx)\n",
>  			  daif_actual, daif_expected);

That was the warning triggered by CI, that stalled the system. Is that
expected? I'm quite sure that in the oob case the DAIF flags are
different, but is WARN_ONCE() expected to completely halt the system?


>  	}
> diff --git a/include/linux/irq-entry-common.h b/include/linux/irq-entry-common.h
> index 58c28b2a8f2b..61a8e129e71f 100644
> --- a/include/linux/irq-entry-common.h
> +++ b/include/linux/irq-entry-common.h
> @@ -600,6 +600,9 @@ irqentry_exit_to_kernel_mode_after_preempt(struct pt_regs *regs, irqentry_state_
>  {
>  	bool synchronized;
>  
> +	if (running_oob())
> +		return;
> +

The enter/exit code moved one layer down, from irqentry_enter() to
irqentry_enter_from_kernel_mode(), so this code needs the oob check as
well.

>  	instrumentation_begin();
>  	synchronized = irqentry_syncstage(state);
>  
> -- 
> 2.54.0