From 4423eb5ae32ec613af3fceee2fe84234e417ee55 Mon Sep 17 00:00:00 2001 From: Nicholas Piggin Date: Thu, 23 Sep 2021 00:54:47 +1000 Subject: [PATCH] powerpc/64/interrupt: make normal synchronous interrupts enable MSR[EE] if possible Make synchronous interrupt handler entry wrappers enable MSR[EE] if MSR[EE] was enabled in the interrupted context. IRQs are soft-disabled at this point so there is no change to high level code, but it's a masked interrupt could fire. This is a performance disadvantage for interrupts which do not later call interrupt_cond_local_irq_enable(), because an an additional mtmsrd or wrtee instruction is executed. However the important synchronous interrupts (e.g., page fault) do enable interrupts, so the performance disadvantage is mostly avoided. In the next patch, MSR[RI] enabling can be combined with MSR[EE] enabling, which mitigates the performance drop for the former and gives a performance advanage for the latter interrupts, on 64s machines. 64e is coming along for the ride for now to avoid divergences with 64s in this tricky code. Signed-off-by: Nicholas Piggin Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20210922145452.352571-2-npiggin@gmail.com --- arch/powerpc/include/asm/interrupt.h | 19 ++++++++++++++++++- 1 file changed, 18 insertions(+), 1 deletion(-) diff --git a/arch/powerpc/include/asm/interrupt.h b/arch/powerpc/include/asm/interrupt.h index 6d414ddc8e24..2ab7e31c823f 100644 --- a/arch/powerpc/include/asm/interrupt.h +++ b/arch/powerpc/include/asm/interrupt.h @@ -151,7 +151,20 @@ static inline void interrupt_enter_prepare(struct pt_regs *regs, struct interrup #ifdef CONFIG_PPC64 if (irq_soft_mask_set_return(IRQS_ALL_DISABLED) == IRQS_ENABLED) trace_hardirqs_off(); - local_paca->irq_happened |= PACA_IRQ_HARD_DIS; + + /* + * If the interrupt was taken with HARD_DIS clear, then enable MSR[EE]. + * Asynchronous interrupts get here with HARD_DIS set (see below), so + * this enables MSR[EE] for synchronous interrupts. IRQs remain + * soft-masked. The interrupt handler may later call + * interrupt_cond_local_irq_enable() to achieve a regular process + * context. + */ + if (!(local_paca->irq_happened & PACA_IRQ_HARD_DIS)) { + if (IS_ENABLED(CONFIG_PPC_IRQ_SOFT_MASK_DEBUG)) + BUG_ON(!(regs->msr & MSR_EE)); + __hard_irq_enable(); + } if (user_mode(regs)) { kuap_lock(); @@ -203,6 +216,10 @@ static inline void interrupt_exit_prepare(struct pt_regs *regs, struct interrupt static inline void interrupt_async_enter_prepare(struct pt_regs *regs, struct interrupt_state *state) { +#ifdef CONFIG_PPC64 + /* Ensure interrupt_enter_prepare does not enable MSR[EE] */ + local_paca->irq_happened |= PACA_IRQ_HARD_DIS; +#endif #ifdef CONFIG_PPC_BOOK3S_64 if (cpu_has_feature(CPU_FTR_CTRL) && !test_thread_local_flags(_TLF_RUNLATCH)) -- 2.11.0