From 96fa4e7df5f274df8b9d7c5662615b9148b2b27f Mon Sep 17 00:00:00 2001 From: Miguel Ojeda Date: Thu, 27 Jan 2022 15:25:38 +0100 Subject: [PATCH 1/2] Revert "Revert "powerpc/64s/interrupt: Don't enable MSR[EE] in irq handlers unless perf is in use"" This reverts commit 827556ec67207d5d53e69f19cdd73a9f83aca843. This is done in order to use the actual fix that will appear in -rc2. Signed-off-by: Miguel Ojeda --- arch/powerpc/include/asm/hw_irq.h | 57 +++++++++++++++++++++++++------ arch/powerpc/kernel/dbell.c | 3 +- arch/powerpc/kernel/irq.c | 3 +- arch/powerpc/kernel/time.c | 31 +++++++++-------- 4 files changed, 67 insertions(+), 27 deletions(-) diff --git a/arch/powerpc/include/asm/hw_irq.h b/arch/powerpc/include/asm/hw_irq.h index 8d6f80101edadd..a58fb4aa6c81d6 100644 --- a/arch/powerpc/include/asm/hw_irq.h +++ b/arch/powerpc/include/asm/hw_irq.h @@ -345,17 +345,54 @@ static inline bool lazy_irq_pending_nocheck(void) bool power_pmu_wants_prompt_pmi(void); /* - * This is called by asynchronous interrupts to conditionally - * re-enable hard interrupts after having cleared the source - * of the interrupt. They are kept disabled if there is a different - * soft-masked interrupt pending that requires hard masking. + * This is called by asynchronous interrupts to check whether to + * conditionally re-enable hard interrupts after having cleared + * the source of the interrupt. They are kept disabled if there + * is a different soft-masked interrupt pending that requires hard + * masking. */ -static inline void may_hard_irq_enable(void) +static inline bool should_hard_irq_enable(void) { - if (!(get_paca()->irq_happened & PACA_IRQ_MUST_HARD_MASK)) { - get_paca()->irq_happened &= ~PACA_IRQ_HARD_DIS; - __hard_irq_enable(); - } +#ifdef CONFIG_PPC_IRQ_SOFT_MASK_DEBUG + WARN_ON(irq_soft_mask_return() == IRQS_ENABLED); + WARN_ON(mfmsr() & MSR_EE); +#endif +#ifdef CONFIG_PERF_EVENTS + /* + * If the PMU is not running, there is not much reason to enable + * MSR[EE] in irq handlers because any interrupts would just be + * soft-masked. + * + * TODO: Add test for 64e + */ + if (IS_ENABLED(CONFIG_PPC_BOOK3S_64) && !power_pmu_wants_prompt_pmi()) + return false; + + if (get_paca()->irq_happened & PACA_IRQ_MUST_HARD_MASK) + return false; + + return true; +#else + return false; +#endif +} + +/* + * Do the hard enabling, only call this if should_hard_irq_enable is true. + */ +static inline void do_hard_irq_enable(void) +{ +#ifdef CONFIG_PPC_IRQ_SOFT_MASK_DEBUG + WARN_ON(irq_soft_mask_return() == IRQS_ENABLED); + WARN_ON(get_paca()->irq_happened & PACA_IRQ_MUST_HARD_MASK); + WARN_ON(mfmsr() & MSR_EE); +#endif + /* + * This allows PMI interrupts (and watchdog soft-NMIs) through. + * There is no other reason to enable this way. + */ + get_paca()->irq_happened &= ~PACA_IRQ_HARD_DIS; + __hard_irq_enable(); } static inline bool arch_irq_disabled_regs(struct pt_regs *regs) @@ -436,7 +473,7 @@ static inline bool arch_irq_disabled_regs(struct pt_regs *regs) return !(regs->msr & MSR_EE); } -static inline bool may_hard_irq_enable(void) +static inline bool should_hard_irq_enable(void) { return false; } diff --git a/arch/powerpc/kernel/dbell.c b/arch/powerpc/kernel/dbell.c index 5545c9cd17c1c9..f55c6fb34a3a03 100644 --- a/arch/powerpc/kernel/dbell.c +++ b/arch/powerpc/kernel/dbell.c @@ -27,7 +27,8 @@ DEFINE_INTERRUPT_HANDLER_ASYNC(doorbell_exception) ppc_msgsync(); - may_hard_irq_enable(); + if (should_hard_irq_enable()) + do_hard_irq_enable(); kvmppc_clear_host_ipi(smp_processor_id()); __this_cpu_inc(irq_stat.doorbell_irqs); diff --git a/arch/powerpc/kernel/irq.c b/arch/powerpc/kernel/irq.c index 8207f97d51e8c6..2cf31a97126ce6 100644 --- a/arch/powerpc/kernel/irq.c +++ b/arch/powerpc/kernel/irq.c @@ -745,7 +745,8 @@ void __do_irq(struct pt_regs *regs) irq = ppc_md.get_irq(); /* We can hard enable interrupts now to allow perf interrupts */ - may_hard_irq_enable(); + if (should_hard_irq_enable()) + do_hard_irq_enable(); /* And finally process it */ if (unlikely(!irq)) diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c index 42df9dd7fb4183..62361cc7281cd7 100644 --- a/arch/powerpc/kernel/time.c +++ b/arch/powerpc/kernel/time.c @@ -609,22 +609,23 @@ DEFINE_INTERRUPT_HANDLER_ASYNC(timer_interrupt) return; } - /* Ensure a positive value is written to the decrementer, or else - * some CPUs will continue to take decrementer exceptions. When the - * PPC_WATCHDOG (decrementer based) is configured, keep this at most - * 31 bits, which is about 4 seconds on most systems, which gives - * the watchdog a chance of catching timer interrupt hard lockups. - */ - if (IS_ENABLED(CONFIG_PPC_WATCHDOG)) - set_dec(0x7fffffff); - else - set_dec(decrementer_max); - - /* Conditionally hard-enable interrupts now that the DEC has been - * bumped to its maximum value - */ - may_hard_irq_enable(); + /* Conditionally hard-enable interrupts. */ + if (should_hard_irq_enable()) { + /* + * Ensure a positive value is written to the decrementer, or + * else some CPUs will continue to take decrementer exceptions. + * When the PPC_WATCHDOG (decrementer based) is configured, + * keep this at most 31 bits, which is about 4 seconds on most + * systems, which gives the watchdog a chance of catching timer + * interrupt hard lockups. + */ + if (IS_ENABLED(CONFIG_PPC_WATCHDOG)) + set_dec(0x7fffffff); + else + set_dec(decrementer_max); + do_hard_irq_enable(); + } #if defined(CONFIG_PPC32) && defined(CONFIG_PPC_PMAC) if (atomic_read(&ppc_n_lost_interrupts) != 0) From 8e5bf284498fcdc269447b292afe7d3f77903c7f Mon Sep 17 00:00:00 2001 From: Nicholas Piggin Date: Tue, 25 Jan 2022 00:39:28 +1000 Subject: [PATCH 2/2] powerpc/64s/interrupt: Fix decrementer storm The decrementer exception can fail to be cleared when the interrupt returns in the case where the decrementer wraps with the next timer still beyond decrementer_max. This results in a decrementer interrupt storm. This is triggerable with small decrementer system with hard and soft watchdogs disabled. Fix this by always programming the decrementer if there was no timer. Fixes: 0faf20a1ad16 ("powerpc/64s/interrupt: Don't enable MSR[EE] in irq handlers unless perf is in use") Reported-by: Alexey Kardashevskiy Signed-off-by: Nicholas Piggin Signed-off-by: Miguel Ojeda --- arch/powerpc/kernel/time.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c index 62361cc7281cd7..cd0b8b71ecddc1 100644 --- a/arch/powerpc/kernel/time.c +++ b/arch/powerpc/kernel/time.c @@ -649,8 +649,9 @@ DEFINE_INTERRUPT_HANDLER_ASYNC(timer_interrupt) __this_cpu_inc(irq_stat.timer_irqs_event); } else { now = *next_tb - now; - if (now <= decrementer_max) - set_dec_or_work(now); + if (now > decrementer_max) + now = decrementer_max; + set_dec_or_work(now); __this_cpu_inc(irq_stat.timer_irqs_others); }