From 768c47010392ece9766a56479b4e0cf04a536916 Mon Sep 17 00:00:00 2001 From: Nicholas Piggin Date: Tue, 5 Oct 2021 00:56:41 +1000 Subject: powerpc/64/interrupt: Reconcile soft-mask state in NMI and fix false BUG If a NMI hits early in an interrupt handler before the irq soft-mask state is reconciled, that can cause a false-positive BUG with a CONFIG_PPC_IRQ_SOFT_MASK_DEBUG assertion. Remove that assertion and instead check the case that if regs->msr has EE clear, then regs->softe should be marked as disabled so the irq state looks correct to NMI handlers, the same as how it's fixed up in the case it was implicit soft-masked. This doesn't fix a known problem -- the change that was fixed by commit 4ec5feec1ad02 ("powerpc/64s: Make NMI record implicitly soft-masked code as irqs disabled") was the addition of a warning in the soft-nmi watchdog interrupt which can never actually fire when MSR[EE]=0. However it may be important if NMI handlers grow more code, and it's less surprising to anything using 'regs' - (I tripped over this when working in the area). Signed-off-by: Nicholas Piggin Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20211004145642.1331214-5-npiggin@gmail.com --- arch/powerpc/include/asm/interrupt.h | 13 ++++++++----- 1 file changed, 8 insertions(+), 5 deletions(-) (limited to 'arch/powerpc/include/asm/interrupt.h') diff --git a/arch/powerpc/include/asm/interrupt.h b/arch/powerpc/include/asm/interrupt.h index 6b800d3e2681..b894b7169706 100644 --- a/arch/powerpc/include/asm/interrupt.h +++ b/arch/powerpc/include/asm/interrupt.h @@ -265,13 +265,16 @@ static inline void interrupt_nmi_enter_prepare(struct pt_regs *regs, struct inte local_paca->irq_soft_mask = IRQS_ALL_DISABLED; local_paca->irq_happened |= PACA_IRQ_HARD_DIS; - if (is_implicit_soft_masked(regs)) { - // Adjust regs->softe soft implicit soft-mask, so - // arch_irq_disabled_regs(regs) behaves as expected. + if (!(regs->msr & MSR_EE) || is_implicit_soft_masked(regs)) { + /* + * Adjust regs->softe to be soft-masked if it had not been + * reconcied (e.g., interrupt entry with MSR[EE]=0 but softe + * not yet set disabled), or if it was in an implicit soft + * masked state. This makes arch_irq_disabled_regs(regs) + * behave as expected. + */ regs->softe = IRQS_ALL_DISABLED; } - if (IS_ENABLED(CONFIG_PPC_IRQ_SOFT_MASK_DEBUG)) - BUG_ON(!arch_irq_disabled_regs(regs) && !(regs->msr & MSR_EE)); /* Don't do any per-CPU operations until interrupt state is fixed */ -- cgit v1.2.3 From f08fb25bc66986b0952724530a640d9970fa52c1 Mon Sep 17 00:00:00 2001 From: Nicholas Piggin Date: Tue, 5 Oct 2021 00:56:42 +1000 Subject: powerpc/64s: Fix unrecoverable MCE calling async handler from NMI MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The machine check handler is not considered NMI on 64s. The early handler is the true NMI handler, and then it schedules the machine_check_exception handler to run when interrupts are enabled. This works fine except the case of an unrecoverable MCE, where the true NMI is taken when MSR[RI] is clear, it can not recover, so it calls machine_check_exception directly so something might be done about it. Calling an async handler from NMI context can result in irq state and other things getting corrupted. This can also trigger the BUG at arch/powerpc/include/asm/interrupt.h:168 BUG_ON(!arch_irq_disabled_regs(regs) && !(regs->msr & MSR_EE)); Fix this by making an _async version of the handler which is called in the normal case, and a NMI version that is called for unrecoverable interrupts. Fixes: 2b43dd7653cc ("powerpc/64: enable MSR[EE] in irq replay pt_regs") Signed-off-by: Nicholas Piggin Tested-by: Cédric Le Goater Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20211004145642.1331214-6-npiggin@gmail.com --- arch/powerpc/include/asm/interrupt.h | 5 ++--- arch/powerpc/kernel/exceptions-64s.S | 8 ++++++-- arch/powerpc/kernel/traps.c | 31 ++++++++++++++++++------------- 3 files changed, 26 insertions(+), 18 deletions(-) (limited to 'arch/powerpc/include/asm/interrupt.h') diff --git a/arch/powerpc/include/asm/interrupt.h b/arch/powerpc/include/asm/interrupt.h index b894b7169706..a1d238255f07 100644 --- a/arch/powerpc/include/asm/interrupt.h +++ b/arch/powerpc/include/asm/interrupt.h @@ -528,10 +528,9 @@ static __always_inline long ____##func(struct pt_regs *regs) /* kernel/traps.c */ DECLARE_INTERRUPT_HANDLER_NMI(system_reset_exception); #ifdef CONFIG_PPC_BOOK3S_64 -DECLARE_INTERRUPT_HANDLER_ASYNC(machine_check_exception); -#else -DECLARE_INTERRUPT_HANDLER_NMI(machine_check_exception); +DECLARE_INTERRUPT_HANDLER_ASYNC(machine_check_exception_async); #endif +DECLARE_INTERRUPT_HANDLER_NMI(machine_check_exception); DECLARE_INTERRUPT_HANDLER(SMIException); DECLARE_INTERRUPT_HANDLER(handle_hmi_exception); DECLARE_INTERRUPT_HANDLER(unknown_exception); diff --git a/arch/powerpc/kernel/exceptions-64s.S b/arch/powerpc/kernel/exceptions-64s.S index 024d9231f88c..eaf1f72131a1 100644 --- a/arch/powerpc/kernel/exceptions-64s.S +++ b/arch/powerpc/kernel/exceptions-64s.S @@ -1243,7 +1243,7 @@ EXC_COMMON_BEGIN(machine_check_common) li r10,MSR_RI mtmsrd r10,1 addi r3,r1,STACK_FRAME_OVERHEAD - bl machine_check_exception + bl machine_check_exception_async b interrupt_return_srr @@ -1303,7 +1303,11 @@ END_FTR_SECTION_IFSET(CPU_FTR_HVMODE) subi r12,r12,1 sth r12,PACA_IN_MCE(r13) - /* Invoke machine_check_exception to print MCE event and panic. */ + /* + * Invoke machine_check_exception to print MCE event and panic. + * This is the NMI version of the handler because we are called from + * the early handler which is a true NMI. + */ addi r3,r1,STACK_FRAME_OVERHEAD bl machine_check_exception diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c index e453b666613b..11741703d26e 100644 --- a/arch/powerpc/kernel/traps.c +++ b/arch/powerpc/kernel/traps.c @@ -796,24 +796,22 @@ void die_mce(const char *str, struct pt_regs *regs, long err) * do_exit() checks for in_interrupt() and panics in that case, so * exit the irq/nmi before calling die. */ - if (IS_ENABLED(CONFIG_PPC_BOOK3S_64)) - irq_exit(); - else + if (in_nmi()) nmi_exit(); + else + irq_exit(); die(str, regs, err); } /* - * BOOK3S_64 does not call this handler as a non-maskable interrupt + * BOOK3S_64 does not usually call this handler as a non-maskable interrupt * (it uses its own early real-mode handler to handle the MCE proper * and then raises irq_work to call this handler when interrupts are - * enabled). + * enabled). The only time when this is not true is if the early handler + * is unrecoverable, then it does call this directly to try to get a + * message out. */ -#ifdef CONFIG_PPC_BOOK3S_64 -DEFINE_INTERRUPT_HANDLER_ASYNC(machine_check_exception) -#else -DEFINE_INTERRUPT_HANDLER_NMI(machine_check_exception) -#endif +static void __machine_check_exception(struct pt_regs *regs) { int recover = 0; @@ -847,12 +845,19 @@ bail: /* Must die if the interrupt is not recoverable */ if (regs_is_unrecoverable(regs)) die_mce("Unrecoverable Machine check", regs, SIGBUS); +} #ifdef CONFIG_PPC_BOOK3S_64 - return; -#else - return 0; +DEFINE_INTERRUPT_HANDLER_ASYNC(machine_check_exception_async) +{ + __machine_check_exception(regs); +} #endif +DEFINE_INTERRUPT_HANDLER_NMI(machine_check_exception) +{ + __machine_check_exception(regs); + + return 0; } DEFINE_INTERRUPT_HANDLER(SMIException) /* async? */ -- cgit v1.2.3