When a CPU is reset, QEMU makes sure no interrupt is pending by clearing CPUPPCstate::pending_interrupts in ppc_cpu_reset(). In the case of a complete machine emulation, eg. a sPAPR machine, an external interrupt request could still be pending in KVM though, eg. an IPI. It will be eventually presented to the guest, which is supposed to acknowledge it at the interrupt controller. If the interrupt controller is emulated in QEMU, either XICS or XIVE, ppc_set_irq() won't deassert the external interrupt pin in KVM since it isn't pending anymore for QEMU. When the vCPU re-enters the guest, the interrupt request is still pending and the vCPU will try again to acknowledge it. This causes an infinite loop and eventually hangs the guest.
The code has been broken since the beginning. The issue wasn't hit before because accel=kvm,kernel-irqchip=off is an awkward setup that never got used until recently with the LC92x IBM systems (aka, Boston). Add a ppc_irq_reset() function to do the necessary cleanup, ie. deassert the IRQ pins of the CPU in QEMU and most importantly the external interrupt pin for this vCPU in KVM. Reported-by: Satheesh Rajendran <sathn...@linux.vnet.ibm.com> Signed-off-by: Greg Kurz <gr...@kaod.org> --- hw/ppc/ppc.c | 8 ++++++++ include/hw/ppc/ppc.h | 2 ++ target/ppc/translate_init.inc.c | 1 + 3 files changed, 11 insertions(+) diff --git a/hw/ppc/ppc.c b/hw/ppc/ppc.c index 8dd982fc1e40..fab73f1b1fc9 100644 --- a/hw/ppc/ppc.c +++ b/hw/ppc/ppc.c @@ -1515,3 +1515,11 @@ PowerPCCPU *ppc_get_vcpu_by_pir(int pir) return NULL; } + +void ppc_irq_reset(PowerPCCPU *cpu) +{ + CPUPPCState *env = &cpu->env; + + env->irq_input_state = 0; + kvmppc_set_interrupt(cpu, PPC_INTERRUPT_EXT, 0); +} diff --git a/include/hw/ppc/ppc.h b/include/hw/ppc/ppc.h index 585be6ab98c5..89e1dd065af7 100644 --- a/include/hw/ppc/ppc.h +++ b/include/hw/ppc/ppc.h @@ -77,6 +77,7 @@ static inline void ppc970_irq_init(PowerPCCPU *cpu) {} static inline void ppcPOWER7_irq_init(PowerPCCPU *cpu) {} static inline void ppcPOWER9_irq_init(PowerPCCPU *cpu) {} static inline void ppce500_irq_init(PowerPCCPU *cpu) {} +static inline void ppc_irq_reset(PowerPCCPU *cpu) {} #else void ppc40x_irq_init(PowerPCCPU *cpu); void ppce500_irq_init(PowerPCCPU *cpu); @@ -84,6 +85,7 @@ void ppc6xx_irq_init(PowerPCCPU *cpu); void ppc970_irq_init(PowerPCCPU *cpu); void ppcPOWER7_irq_init(PowerPCCPU *cpu); void ppcPOWER9_irq_init(PowerPCCPU *cpu); +void ppc_irq_reset(PowerPCCPU *cpu); #endif /* PPC machines for OpenBIOS */ diff --git a/target/ppc/translate_init.inc.c b/target/ppc/translate_init.inc.c index ba726dec4d00..64a838095c7a 100644 --- a/target/ppc/translate_init.inc.c +++ b/target/ppc/translate_init.inc.c @@ -10461,6 +10461,7 @@ static void ppc_cpu_reset(CPUState *s) env->pending_interrupts = 0; s->exception_index = POWERPC_EXCP_NONE; env->error_code = 0; + ppc_irq_reset(cpu); /* tininess for underflow is detected before rounding */ set_float_detect_tininess(float_tininess_before_rounding,