[RFC PATCH 30/36] arm64: irq: Report FEAT_NMI masking local IRQs

[Jinjie Ruan]

On 7/9/2026 8:13 PM, Vladimir Murzin wrote:
> From: Ada Couprie Diaz <ada.coupriediaz at arm.com>
> 
> As we clear SCTLR_EL1.SPINTMASK when enabling FEAT_NMI, ALLINT masks
> IRQs and FIQs regardless of superpriority.
> Update irqflags.h and `regs_irqs_disabled()` to take it into account,
> so we properly keep track of
> 
> We have documentation at the top of irqflags.h which explains the DAIF
> masking. Since the additional masking with NMIs is related and also
> covers the IF in DAIF, extend the comment to note what's going on
> with NMIs.
> 
> Co-developed-by: Mark Brown <broonie at kernel.org>
> Signed-off-by: Mark Brown <broonie at kernel.org>
> Signed-off-by: Ada Couprie Diaz <ada.coupriediaz at arm.com>
> Signed-off-by: Vladimir Murzin <vladimir.murzin at arm.com>
> ---
>  arch/arm64/include/asm/irqflags.h | 17 +++++++++++++++++
>  arch/arm64/include/asm/ptrace.h   |  9 ++++++++-
>  2 files changed, 25 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/include/asm/irqflags.h b/arch/arm64/include/asm/irqflags.h
> index b571d34bf11d..a291a231d644 100644
> --- a/arch/arm64/include/asm/irqflags.h
> +++ b/arch/arm64/include/asm/irqflags.h
> @@ -20,6 +20,16 @@
>   * always masked and unmasked together, and have no side effects for other
>   * flags. Keeping to this order makes it easier for entry.S to know which
>   * exceptions should be unmasked.
> + *
> + * With the addition of the FEAT_NMI extension we gain an additional
> + * class of superpriority IRQ/FIQ which is separately masked with a
> + * choice of modes controlled by SCTLR_ELn.{SPINTMASK,NMI}.
> + * Linux sets SPINTMASK to 0 and NMI to 1 which results in ALLINT.ALLINT
> + * masking both superpriority interrupts and IRQ/FIQ regardless of the
> + * I and F settings. Since these superpriority interrupts are being
> + * used as NMIs we do not include them in the interrupt masking here,
> + * anything that requires that NMIs be masked needs to explicitly do so,
> + * but we do check for ALLINT masking IRQs/FIQs.
>   */
>  
>   /*
> @@ -103,6 +113,9 @@ static __always_inline unsigned long arch_local_save_flags(void)
>  {
>  	arm64_exc_hwstate_t hwstate = { .daif = read_sysreg(daif) };
>  
> +	if (system_uses_nmi())
> +		hwstate.allint = read_sysreg_s(SYS_ALLINT);
> +
>  	if (system_uses_irq_prio_masking())
>  		hwstate.pmr = read_sysreg_s(SYS_ICC_PMR_EL1);
>  
> @@ -117,6 +130,10 @@ static __always_inline bool arch_irqs_disabled_flags(unsigned long flags)
>  	if (hwstate.daif & PSR_I_BIT)
>  		return true;
>  
> +	/* SCTLR_EL1.SPINTMASK is clear, so ALLINT masks *all* IRQs/FIQs. */
> +	if (system_uses_nmi() && hwstate.allint > 0)

The ">0" here doesn't seem very rigorous, maybe:

if (system_uses_nmi() && hwstate.allint & ALLINT_ALLINT)

> +		return true;
> +
>  	if (system_uses_irq_prio_masking() && hwstate.pmr < GIC_PRIO_IRQON)
>  		return true;
>  
> diff --git a/arch/arm64/include/asm/ptrace.h b/arch/arm64/include/asm/ptrace.h
> index c630165882e8..096d85d75bd7 100644
> --- a/arch/arm64/include/asm/ptrace.h
> +++ b/arch/arm64/include/asm/ptrace.h
> @@ -206,9 +206,16 @@ static inline void forget_syscall(struct pt_regs *regs)
>  		(regs)->pmr >= GIC_PRIO_IRQON :				\
>  		true)
>  
> +#define irqs_allint_clear(regs)				\
> +	(system_uses_nmi() ?				\
> +		((regs)->pstate & PSR_ALLINT_BIT) == 0:	\
> +		true)
> +
>  static __always_inline bool regs_irqs_disabled(const struct pt_regs *regs)
>  {
> -	return (regs->pstate & PSR_I_BIT) || !irqs_priority_unmasked(regs);
> +	return (regs->pstate & PSR_I_BIT) ||
> +		!irqs_priority_unmasked(regs) ||
> +		!irqs_allint_clear(regs);

Why not define the logic for disable? The semantics of
regs_irqs_disabled() is "interrupts disabled".

204 #define
irqs_priority_masked(regs)>----->------->------->------->-------\
205 >-------(system_uses_irq_prio_masking()
?>------>------->------->-------\
206 >------->-------(regs)->pmr == GIC_PRIO_IRQOFF
:>------->------->-------\
207 >------->-------false)
208
209 #define irqs_allint_masked(regs)>------->------->------->-------\
210 >-------(system_uses_nmi() ?>--->------->------->-------\
211 >------->-------((regs)->pstate & PSR_ALLINT_BIT) :>----\
212 >------->-------false)
213
214 static __always_inline bool regs_irqs_disabled(const struct pt_regs
*regs)
215 {
216 >-------return (regs->pstate & PSR_I_BIT) ||
217 >------->-------irqs_priority_masked(regs) ||
218 >------->-------irqs_allint_masked(regs);

otherwise, LGTM
Reviewed-by: Jinjie Ruan <ruanjinjie at huawei.com>

>  }
>  
>  #define interrupts_enabled(regs)	(!regs_irqs_disabled(regs))