ppc: Deassert the external interrupt pin in KVM on reset

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 <[email protected]>
Signed-off-by: Greg Kurz <[email protected]>
Message-Id: <157548861740.3650476.16879693165328764758[email protected]>
Signed-off-by: David Gibson <[email protected]>

diff --git a/hw/ppc/ppc.c b/hw/ppc/ppc.c
index 8dd982fc1e405603c236396feeaa7e1651632880..fab73f1b1fc93a18d84c9af87656adad77408678 100644 (file)
--- 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 585be6ab98c57a8777a91a8c319553779334c052..89e1dd065af779d6a3a7f3923bea82fe8c8e2e16 100644 (file)
--- 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 ba726dec4d0030346cee8cad2b1ec4578dbe2114..64a838095c7a04852bdb454c8c4b8abe5de543bb 100644 (file)
--- 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,