Re: [RFC PATCH 10/36] arm64: irqflags: save and use both DAIF and PMR

[Jinjie Ruan <ruanjinjie@huawei.com>]

On 7/9/2026 8:13 PM, Vladimir Murzin wrote:
> From: Ada Couprie Diaz <ada.coupriediaz@arm.com>
> 
> With pseudo-NMIs enabled, both DAIF and the PMR affect interrupt masking.
> Now that we have a type which can track both of them at the same time,
> update our irqflags implementation to use it.
> 
> Save DAIF flags in all cases, as they can be manipulated directly by other
> code, and the PMR if it is in use.
> 
> When checking if IRQs are disabled, now that we always save DAIF we can
> check that the I flag is set and bypass checking the PMR if it is.
> We can also properly check if PMR masks interrupts (PMR < GIC_PRIO_IRQON),
> now that we don't need to rely on the GIC_PRIO_PSR_I_SET bit being set in
> the PMR to know if DAIF is already masking interrupts.
> Update `irqs_priority_unmasked()` to align with this change.
> 
> This allows us to remove the `__daif_...` and `__pmr_...` versions
> of the save and check functions, as they are now unified.
> 
> We can reasonably merge the two `__{daif,pmr}_irq_restore()` functions
> in the main one, as the DAIF and PMR values are properly split now.
> 
> Signed-off-by: Ada Couprie Diaz <ada.coupriediaz@arm.com>
> Signed-off-by: Vladimir Murzin <vladimir.murzin@arm.com>
> ---
>  arch/arm64/include/asm/irqflags.h | 110 ++++++------------------------
>  arch/arm64/include/asm/ptrace.h   |   2 +-
>  2 files changed, 23 insertions(+), 89 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/irqflags.h b/arch/arm64/include/asm/irqflags.h
> index 7775904ba6a9..62f047702493 100644
> --- a/arch/arm64/include/asm/irqflags.h
> +++ b/arch/arm64/include/asm/irqflags.h
> @@ -95,117 +95,48 @@ static __always_inline void arch_local_irq_disable(void)
>  	}
>  }
>  
> -static __always_inline arm64_exc_hwstate_t __daif_local_save_flags(void)
> -{
> -	return (arm64_exc_hwstate_t){ .daif = read_sysreg(daif) };
> -}
> -
> -static __always_inline arm64_exc_hwstate_t __pmr_local_save_flags(void)
> -{
> -	return (arm64_exc_hwstate_t){ .pmr = read_sysreg_s(SYS_ICC_PMR_EL1) };
> -}
> -
>  /*
>   * Save the current interrupt enable state.
>   */
>  static __always_inline unsigned long arch_local_save_flags(void)
>  {
> -	if (system_uses_irq_prio_masking()) {
> -		return __pmr_local_save_flags().flags;
> -	} else {
> -		return __daif_local_save_flags().flags;
> -	}
> -}
> +	arm64_exc_hwstate_t hwstate = { .daif = read_sysreg(daif) };
>  
> -static __always_inline
> -bool __daif_irqs_disabled_flags(arm64_exc_hwstate_t hwstate)
> -{
> -	return hwstate.daif & PSR_I_BIT;
> -}
> +	if (system_uses_irq_prio_masking())
> +		hwstate.pmr = read_sysreg_s(SYS_ICC_PMR_EL1);
>  
> -static __always_inline
> -bool __pmr_irqs_disabled_flags(arm64_exc_hwstate_t hwstate)
> -{
> -	return hwstate.pmr != GIC_PRIO_IRQON;
> +	return hwstate.flags;
>  }
>  
>  static __always_inline bool arch_irqs_disabled_flags(unsigned long flags)
>  {
>  	arm64_exc_hwstate_t hwstate = { .flags = flags };
>  
> -	if (system_uses_irq_prio_masking()) {
> -		return __pmr_irqs_disabled_flags(hwstate);
> -	} else {
> -		return __daif_irqs_disabled_flags(hwstate);
> -	}
> -}
> +	/* If I is set, the PMR doesn't matter: interrupts will not be taken. */
> +	if (hwstate.daif & PSR_I_BIT)
> +		return true;
>  
> -static __always_inline bool __daif_irqs_disabled(void)
> -{
> -	return __daif_irqs_disabled_flags(__daif_local_save_flags());
> -}
> +	if (system_uses_irq_prio_masking() && hwstate.pmr < GIC_PRIO_IRQON)

This concept of being less than or greater than is not easy to understand.

> +		return true;
>  
> -static __always_inline bool __pmr_irqs_disabled(void)
> -{
> -	return __pmr_irqs_disabled_flags(__pmr_local_save_flags());
> +	return false;
>  }
>  
>  static __always_inline bool arch_irqs_disabled(void)
>  {
> -	if (system_uses_irq_prio_masking()) {
> -		return __pmr_irqs_disabled();
> -	} else {
> -		return __daif_irqs_disabled();
> -	}
> -}
> -
> -static __always_inline arm64_exc_hwstate_t __daif_local_irq_save(void)
> -{
> -	arm64_exc_hwstate_t hwstate = __daif_local_save_flags();
> -
> -	__daif_local_irq_disable();
> -
> -	return hwstate;
> -}
> -
> -static __always_inline arm64_exc_hwstate_t __pmr_local_irq_save(void)
> -{
> -	arm64_exc_hwstate_t hwstate = __pmr_local_save_flags();
> -
> -	/*
> -	 * There are too many states with IRQs disabled, just keep the current
> -	 * state if interrupts are already disabled/masked.
> -	 */
> -	if (!__pmr_irqs_disabled_flags(hwstate))
> -		__pmr_local_irq_disable();
> -
> -	return hwstate;
> +	return arch_irqs_disabled_flags(arch_local_save_flags());
>  }
>  
>  static __always_inline unsigned long arch_local_irq_save(void)
>  {
> -	if (system_uses_irq_prio_masking()) {
> -		return __pmr_local_irq_save().flags;
> -	} else {
> -		return __daif_local_irq_save().flags;
> -	}
> -}
> +	unsigned long flags = arch_local_save_flags();
>  
> -static __always_inline
> -void __daif_local_irq_restore(arm64_exc_hwstate_t hwstate)
> -{
> -	barrier();
> -	write_sysreg(hwstate.daif, daif);
> -	barrier();
> -}
> +	if (system_uses_irq_prio_masking())
> +		__pmr_local_irq_disable();
> +	else
> +		__daif_local_irq_disable();
>  
> -static __always_inline
> -void __pmr_local_irq_restore(arm64_exc_hwstate_t hwstate)
> -{
> -	barrier();
> -	write_sysreg_s(hwstate.pmr, SYS_ICC_PMR_EL1);
> -	pmr_sync();
> -	barrier();
> +	return flags;
>  }
>  
>  /*
> @@ -215,11 +146,14 @@ static __always_inline void arch_local_irq_restore(unsigned long flags)
>  {
>  	arm64_exc_hwstate_t hwstate = { .flags = flags };
>  
> +	barrier();
>  	if (system_uses_irq_prio_masking()) {
> -		__pmr_local_irq_restore(hwstate);
> +		write_sysreg_s(hwstate.pmr, SYS_ICC_PMR_EL1);
> +		pmr_sync();
>  	} else {
> -		__daif_local_irq_restore(hwstate);
> +		write_sysreg(hwstate.daif, daif);
>  	}
> +	barrier();
>  }
>  
>  #endif /* __ASM_IRQFLAGS_H */
> diff --git a/arch/arm64/include/asm/ptrace.h b/arch/arm64/include/asm/ptrace.h
> index f7dc5fb9427d..192eb97cd50b 100644
> --- a/arch/arm64/include/asm/ptrace.h
> +++ b/arch/arm64/include/asm/ptrace.h
> @@ -205,7 +205,7 @@ static inline void forget_syscall(struct pt_regs *regs)
>  
>  #define irqs_priority_unmasked(regs)					\
>  	(system_uses_irq_prio_masking() ?				\
> -		(regs)->pmr == GIC_PRIO_IRQON :				\
> +		(regs)->pmr >= GIC_PRIO_IRQON :				\
>  		true)
>  
>  static __always_inline bool regs_irqs_disabled(const struct pt_regs *regs)