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Message-ID: <3de95000-19ce-499e-b6b6-7e207c02c73c@kernel.org>
Date: Tue, 16 Dec 2025 11:43:02 +0100
From: "Christophe Leroy (CS GROUP)" <chleroy@...nel.org>
To: Mukesh Kumar Chaurasiya <mkchauras@...ux.ibm.com>, maddy@...ux.ibm.com,
mpe@...erman.id.au, npiggin@...il.com, oleg@...hat.com, kees@...nel.org,
luto@...capital.net, wad@...omium.org, mchauras@...ux.ibm.com,
thuth@...hat.com, sshegde@...ux.ibm.com, charlie@...osinc.com,
macro@...am.me.uk, akpm@...ux-foundation.org, ldv@...ace.io, deller@....de,
ankur.a.arora@...cle.com, segher@...nel.crashing.org, tglx@...utronix.de,
thomas.weissschuh@...utronix.de, peterz@...radead.org,
menglong8.dong@...il.com, bigeasy@...utronix.de, namcao@...utronix.de,
kan.liang@...ux.intel.com, mingo@...nel.org, atrajeev@...ux.vnet.ibm.com,
mark.barnett@....com, linuxppc-dev@...ts.ozlabs.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 7/8] powerpc: Enable IRQ generic entry/exit path.
Le 14/12/2025 à 14:02, Mukesh Kumar Chaurasiya a écrit :
> From: Mukesh Kumar Chaurasiya <mchauras@...ux.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@...ux.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
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