Re: [PATCH v2 7/8] powerpc: Enable IRQ generic entry/exit path.

["Christophe Leroy (CS GROUP)" <chleroy@kernel.org>]

Le 14/12/2025 à 14:02, Mukesh Kumar Chaurasiya a écrit :
> From: Mukesh Kumar Chaurasiya <mchauras@linux.ibm.com>
> 
> Enable the generic IRQ entry/exit infrastructure on PowerPC by selecting
> GENERIC_IRQ_ENTRY and integrating the architecture-specific interrupt
> handlers with the generic entry/exit APIs.
> 
> This change replaces PowerPC’s local interrupt entry/exit handling with
> calls to the generic irqentry_* helpers, aligning the architecture with
> the common kernel entry model. The macros that define interrupt, async,
> and NMI handlers are updated to use irqentry_enter()/irqentry_exit()
> and irqentry_nmi_enter()/irqentry_nmi_exit() where applicable.
> 
> Key updates include:
>   - Select GENERIC_IRQ_ENTRY in Kconfig.
>   - Replace interrupt_enter/exit_prepare() with arch_interrupt_* helpers.
>   - Integrate irqentry_enter()/exit() in standard and async interrupt paths.
>   - Integrate irqentry_nmi_enter()/exit() in NMI handlers.
>   - Remove redundant irq_enter()/irq_exit() calls now handled generically.
>   - Use irqentry_exit_cond_resched() for preemption checks.
> 
> This change establishes the necessary wiring for PowerPC to use the
> generic IRQ entry/exit framework while maintaining existing semantics.

Did you look into resulting code ?

do_IRQ() is bigger and calls irqentry_enter() which is bigger than 
irq_enter().

And irq_enter_rcu() was tail-called from irq_enter(), now is it called 
after irqentry_enter().

> 
> Signed-off-by: Mukesh Kumar Chaurasiya <mchauras@linux.ibm.com>
> ---
>   arch/powerpc/Kconfig                    |   1 +
>   arch/powerpc/include/asm/entry-common.h |  66 +---
>   arch/powerpc/include/asm/interrupt.h    | 499 +++---------------------
>   arch/powerpc/kernel/interrupt.c         |  13 +-
>   4 files changed, 74 insertions(+), 505 deletions(-)
> 
> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
> index e24f4d88885a..b0c602c3bbe1 100644
> --- a/arch/powerpc/Kconfig
> +++ b/arch/powerpc/Kconfig
> @@ -206,6 +206,7 @@ config PPC
>   	select GENERIC_GETTIMEOFDAY
>   	select GENERIC_IDLE_POLL_SETUP
>   	select GENERIC_IOREMAP
> +	select GENERIC_IRQ_ENTRY
>   	select GENERIC_IRQ_SHOW
>   	select GENERIC_IRQ_SHOW_LEVEL
>   	select GENERIC_PCI_IOMAP		if PCI
> diff --git a/arch/powerpc/include/asm/entry-common.h b/arch/powerpc/include/asm/entry-common.h
> index e8bde4c67eaf..e2ae7416dee1 100644
> --- a/arch/powerpc/include/asm/entry-common.h
> +++ b/arch/powerpc/include/asm/entry-common.h
> @@ -257,6 +257,17 @@ static inline void arch_interrupt_enter_prepare(struct pt_regs *regs)
>    */
>   static inline void arch_interrupt_exit_prepare(struct pt_regs *regs)
>   {
> +	if (user_mode(regs)) {
> +		BUG_ON(regs_is_unrecoverable(regs));
> +		BUG_ON(regs_irqs_disabled(regs));
> +		/*
> +		 * We don't need to restore AMR on the way back to userspace for KUAP.
> +		 * AMR can only have been unlocked if we interrupted the kernel.
> +		 */
> +		kuap_assert_locked();
> +
> +		local_irq_disable();
> +	}
>   }
>   
>   static inline void arch_interrupt_async_enter_prepare(struct pt_regs *regs)
> @@ -275,7 +286,6 @@ static inline void arch_interrupt_async_enter_prepare(struct pt_regs *regs)
>   	    !test_thread_local_flags(_TLF_RUNLATCH))
>   		__ppc64_runlatch_on();
>   #endif
> -	irq_enter();
>   }
>   
>   static inline void arch_interrupt_async_exit_prepare(struct pt_regs *regs)
> @@ -288,7 +298,6 @@ static inline void arch_interrupt_async_exit_prepare(struct pt_regs *regs)
>   	 */
>   	nap_adjust_return(regs);
>   
> -	irq_exit();
>   	arch_interrupt_exit_prepare(regs);
>   }
>   
> @@ -354,59 +363,11 @@ static inline void arch_interrupt_nmi_enter_prepare(struct pt_regs *regs,
>   		this_cpu_set_ftrace_enabled(0);
>   	}
>   #endif
> -
> -	/* If data relocations are enabled, it's safe to use nmi_enter() */
> -	if (mfmsr() & MSR_DR) {
> -		nmi_enter();
> -		return;
> -	}
> -
> -	/*
> -	 * But do not use nmi_enter() for pseries hash guest taking a real-mode
> -	 * NMI because not everything it touches is within the RMA limit.
> -	 */
> -	if (IS_ENABLED(CONFIG_PPC_BOOK3S_64) &&
> -	    firmware_has_feature(FW_FEATURE_LPAR) &&
> -	    !radix_enabled())
> -		return;
> -
> -	/*
> -	 * Likewise, don't use it if we have some form of instrumentation (like
> -	 * KASAN shadow) that is not safe to access in real mode (even on radix)
> -	 */
> -	if (IS_ENABLED(CONFIG_KASAN))
> -		return;
> -
> -	/*
> -	 * Likewise, do not use it in real mode if percpu first chunk is not
> -	 * embedded. With CONFIG_NEED_PER_CPU_PAGE_FIRST_CHUNK enabled there
> -	 * are chances where percpu allocation can come from vmalloc area.
> -	 */
> -	if (percpu_first_chunk_is_paged)
> -		return;
> -
> -	/* Otherwise, it should be safe to call it */
> -	nmi_enter();
>   }
>   
>   static inline void arch_interrupt_nmi_exit_prepare(struct pt_regs *regs,
>   					      struct interrupt_nmi_state *state)
>   {
> -	if (mfmsr() & MSR_DR) {
> -		// nmi_exit if relocations are on
> -		nmi_exit();
> -	} else if (IS_ENABLED(CONFIG_PPC_BOOK3S_64) &&
> -		   firmware_has_feature(FW_FEATURE_LPAR) &&
> -		   !radix_enabled()) {
> -		// no nmi_exit for a pseries hash guest taking a real mode exception
> -	} else if (IS_ENABLED(CONFIG_KASAN)) {
> -		// no nmi_exit for KASAN in real mode
> -	} else if (percpu_first_chunk_is_paged) {
> -		// no nmi_exit if percpu first chunk is not embedded
> -	} else {
> -		nmi_exit();
> -	}
> -
>   	/*
>   	 * nmi does not call nap_adjust_return because nmi should not create
>   	 * new work to do (must use irq_work for that).
> @@ -435,6 +396,8 @@ static inline void arch_interrupt_nmi_exit_prepare(struct pt_regs *regs,
>   
>   static __always_inline void arch_enter_from_user_mode(struct pt_regs *regs)
>   {
> +	kuap_lock();
> +

A reason why this change comes now and not in the patch that added 
arch_enter_from_user_mode() ?

>   	if (IS_ENABLED(CONFIG_PPC_IRQ_SOFT_MASK_DEBUG))
>   		BUG_ON(irq_soft_mask_return() != IRQS_ALL_DISABLED);
>   
> @@ -467,11 +430,8 @@ static __always_inline void arch_enter_from_user_mode(struct pt_regs *regs)
>   	} else
>   #endif
>   		kuap_assert_locked();
> -
>   	booke_restore_dbcr0();
> -

This is cosmetic, should have been done when adding 
arch_enter_from_user_mode()

>   	account_cpu_user_entry();
> -
>   	account_stolen_time();
>   
>   	/*


Christophe