kvm: Decouple 'async interrupt delivery' from 'kernel irqchip'

On x86 userspace delivers interrupts to the kernel asynchronously
(and therefore VCPU idle management is done in the kernel) if and
only if there is an in-kernel irqchip. On other architectures this
isn't necessarily true (they may always send interrupts
asynchronously), so define a new kvm_async_interrupts_enabled()
function instead of misusing kvm_irqchip_in_kernel().
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>
Signed-off-by: NAvi Kivity <avi@redhat.com>

cpus.c

@@ -70,7 +70,8 @@ static bool cpu_thread_is_idle(CPUArchState *env)
     if (env->stopped || !runstate_is_running()) {
         return true;
     }
-    if (!env->halted || qemu_cpu_has_work(env) || kvm_irqchip_in_kernel()) {
+    if (!env->halted || qemu_cpu_has_work(env) ||
+        kvm_async_interrupts_enabled()) {
         return false;
     }
     return true;

kvm-all.c

@@ -100,6 +100,7 @@ struct KVMState
 
 KVMState *kvm_state;
 bool kvm_kernel_irqchip;
+bool kvm_async_interrupts_allowed;
 
 static const KVMCapabilityInfo kvm_required_capabilites[] = {
     KVM_CAP_INFO(USER_MEMORY),
@@ -857,7 +858,7 @@ int kvm_irqchip_set_irq(KVMState *s, int irq, int level)
     struct kvm_irq_level event;
     int ret;
 
-    assert(kvm_irqchip_in_kernel());
+    assert(kvm_async_interrupts_enabled());
 
     event.level = level;
     event.irq = irq;
@@ -1201,6 +1202,10 @@ static int kvm_irqchip_create(KVMState *s)
         s->irqchip_inject_ioctl = KVM_IRQ_LINE_STATUS;
     }
     kvm_kernel_irqchip = true;
+    /* If we have an in-kernel IRQ chip then we must have asynchronous
+     * interrupt delivery (though the reverse is not necessarily true)
+     */
+    kvm_async_interrupts_allowed = true;
 
     kvm_init_irq_routing(s);
 

kvm-stub.c

@@ -19,6 +19,7 @@
 
 KVMState *kvm_state;
 bool kvm_kernel_irqchip;
+bool kvm_async_interrupts_allowed;
 
 int kvm_init_vcpu(CPUArchState *env)
 {

kvm.h

@@ -24,13 +24,26 @@
 
 extern int kvm_allowed;
 extern bool kvm_kernel_irqchip;
+extern bool kvm_async_interrupts_allowed;
 
 #if defined CONFIG_KVM || !defined NEED_CPU_H
 #define kvm_enabled()           (kvm_allowed)
 #define kvm_irqchip_in_kernel() (kvm_kernel_irqchip)
+
+/**
+ * kvm_async_interrupts_enabled:
+ *
+ * Returns: true if we can deliver interrupts to KVM
+ * asynchronously (ie by ioctl from any thread at any time)
+ * rather than having to do interrupt delivery synchronously
+ * (where the vcpu must be stopped at a suitable point first).
+ */
+#define kvm_async_interrupts_enabled() (kvm_async_interrupts_allowed)
+
 #else
 #define kvm_enabled()           (0)
 #define kvm_irqchip_in_kernel() (false)
+#define kvm_async_interrupts_enabled() (false)
 #endif
 
 struct kvm_run;