KVM: PPC: Add level based interrupt logic

KVM on PowerPC used to have completely broken interrupt logic. Usually,
interrupts work by having a PIC that pulls a line up/down, so the CPU knows
that an interrupt is active. This line stays active until some action is
done to the PIC to release the line.

On KVM for PPC, we just checked if there was an interrupt pending and pulled
a line in the kernel module. We never released it though, hoping that kernel
space would just declare an interrupt as released when injected - which is
wrong.

To fix this, we need to completely redesign the interrupt injection logic.
Whenever an interrupt line gets triggered, we need to notify kernel space
that the line is up. Whenever it gets released, we do the same. This way
we can assure that the interrupt state is always known to kernel space.

This fixes random stalls in KVM guests on PowerPC that were waiting for
an interrupt while everyone else thought they received it already.

Signed-off-by: Alexander Graf <agraf@suse.de>

1 files changed, 11 insertions, 0 deletions

diff --git a/hw/ppc.c b/hw/ppc.c
index 2a77eb9..55e3808 100644
--- a/hw/ppc.c
+++ b/hw/ppc.c
@@ -28,6 +28,8 @@
 #include "nvram.h"
 #include "qemu-log.h"
 #include "loader.h"
+#include "kvm.h"
+#include "kvm_ppc.h"
 
 //#define PPC_DEBUG_IRQ
 //#define PPC_DEBUG_TB
@@ -50,6 +52,8 @@ static void cpu_ppc_tb_start (CPUState *env);
 
 static void ppc_set_irq (CPUState *env, int n_IRQ, int level)
 {
+    unsigned int old_pending = env->pending_interrupts;
+
     if (level) {
         env->pending_interrupts |= 1 << n_IRQ;
         cpu_interrupt(env, CPU_INTERRUPT_HARD);
@@ -58,6 +62,13 @@ static void ppc_set_irq (CPUState *env, int n_IRQ, int level)
         if (env->pending_interrupts == 0)
             cpu_reset_interrupt(env, CPU_INTERRUPT_HARD);
     }
+
+    if (old_pending != env->pending_interrupts) {
+#ifdef CONFIG_KVM
+        kvmppc_set_interrupt(env, n_IRQ, level);
+#endif
+    }
+
     LOG_IRQ("%s: %p n_IRQ %d level %d => pending %08" PRIx32
                 "req %08x\n", __func__, env, n_IRQ, level,
                 env->pending_interrupts, env->interrupt_request);