From 63a7531ca31f9f097d9cc1cc3fe86ae683cdabdd Mon Sep 17 00:00:00 2001 From: "Mukesh Kumar Chaurasiya (IBM)" Date: Fri, 4 Sep 2026 14:38:58 +0530 Subject: [PATCH] powerpc/entry: Fix irq_soft_mask corruption on replayed interrupt exit When __replay_soft_interrupts() replays a pending interrupt (e.g. PACA_IRQ_DEC -> timer_interrupt), it calls the handler directly with a synthetic pt_regs. The DEFINE_INTERRUPT_HANDLER_ASYNC wrapper around each handler calls arch_interrupt_async_exit_prepare() on the way out, which calls arch_interrupt_exit_prepare() -> local_irq_disable() -> arch_local_irq_disable(), which does: irq_soft_mask_set(IRQS_DISABLED) /* 0x1 */ This unconditionally overwrites irq_soft_mask with IRQS_DISABLED (0x1), stripping the IRQS_PMI_DISABLED (0x2) bit. The result is that irq_soft_mask is 0x1 instead of IRQS_ALL_DISABLED (0x3) when the handler returns to __replay_soft_interrupts(). For a normally-taken interrupt this is harmless: the next interrupt always enters through arch_interrupt_enter_prepare() which unconditionally sets irq_soft_mask to IRQS_ALL_DISABLED. But during replay, next_interrupt() is called directly between replayed handlers without going back through arch_interrupt_enter_prepare(), so the stripped bit is never restored. next_interrupt() then fires a WARNING: WARNING: arch/powerpc/kernel/irq_64.c:75 WARN_ON(irq_soft_mask_return() != IRQS_ALL_DISABLED) The warning was observed early in boot on a POWER10 pseries guest during kmem_cache_init_late(), where a spinlock release triggers interrupt replay that processes a pending timer interrupt. Debugger state confirming the bug: Before timer_interrupt(®s): irq_soft_mask = 0x3 (IRQS_ALL_DISABLED) correct irq_happened = 0x41 (HARD_DIS|REPLAYING) correct After timer_interrupt(®s) returns: irq_soft_mask = 0x1 (IRQS_DISABLED) WRONG - PMI bit stripped irq_happened = 0x41 unchanged The fix is to replace local_irq_disable() with hard_irq_disable(). hard_irq_disable() is the right primitive here for two reasons: 1. On PPC64 (hw_irq.h:301) it calls irq_soft_mask_set_return(IRQS_ALL_DISABLED), setting the soft mask to 0x3 (both IRQS_DISABLED and IRQS_PMI_DISABLED), which preserves the PMI bit and fixes the WARNING. The additional work it does (__hard_irq_disable(), PACA_IRQ_HARD_DIS |=) is redundant but safe since both are already set at this point in the exit path; the trace_hardirqs_off() inside is guarded by if (!arch_irqs_disabled_flags(flags)) so it will not double-fire. 2. On PPC32 (hw_irq.h:467) hard_irq_disable() maps to arch_local_irq_disable() -> __hard_irq_disable(), which clears MSR[EE] in hardware. This is exactly correct: PPC32 has no soft-mask PACA mechanism, so the hardware disable is the right way to satisfy irqentry_exit()'s requirement. This also fixes a build error on PPC32 where irq_soft_mask_set() is only defined under CONFIG_PPC64: arch/powerpc/include/asm/entry-common.h:273: error: implicit declaration of function 'irq_soft_mask_set' Using hard_irq_disable() requires no #ifdef and is consistent with how the rest of the entry code (e.g. entry-common.h:463) handles the same PPC32/PPC64 split. Fixes: 334f3f6d7a16 ("powerpc/entry: Disable interrupts before irqentry_exit") Reported-by: Venkat Rao Bagalkote Closes: https://lore.kernel.org/all/6f9bfb0f-b14c-468e-bb9f-c157d120d0dc@linux.ibm.com/ Tested-by: Venkat Rao Bagalkote Reviewed-by: Shrikanth Hegde Signed-off-by: Mukesh Kumar Chaurasiya (IBM) Signed-off-by: Madhavan Srinivasan Link: https://patch.msgid.link/20260904090858.128563-1-mkchauras@gmail.com --- arch/powerpc/include/asm/entry-common.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/powerpc/include/asm/entry-common.h b/arch/powerpc/include/asm/entry-common.h index 94083516df57..80b07750b531 100644 --- a/arch/powerpc/include/asm/entry-common.h +++ b/arch/powerpc/include/asm/entry-common.h @@ -270,7 +270,7 @@ static inline void arch_interrupt_exit_prepare(struct pt_regs *regs) } /* irqentry_exit expects to be called with interrupts disabled */ - local_irq_disable(); + hard_irq_disable(); } static inline void arch_interrupt_async_enter_prepare(struct pt_regs *regs)