3 files changed, 52 insertions, 0 deletions

diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c
index 5a144ec..3c37955 100644
--- a/target/i386/kvm/kvm.c
+++ b/target/i386/kvm/kvm.c
@@ -4990,6 +4990,17 @@ MemTxAttrs kvm_arch_post_run(CPUState *cpu, struct kvm_run *run)
         kvm_rate_limit_on_bus_lock();
     }
 
+    /*
+     * If the callback is asserted as a GSI (or PCI INTx) then check if
+     * vcpu_info->evtchn_upcall_pending has been cleared, and deassert
+     * the callback IRQ if so. Ideally we could hook into the PIC/IOAPIC
+     * EOI and only resample then, exactly how the VFIO eventfd pairs
+     * are designed to work for level triggered interrupts.
+     */
+    if (x86_cpu->env.xen_callback_asserted) {
+        kvm_xen_maybe_deassert_callback(cpu);
+    }
+
     /* We need to protect the apic state against concurrent accesses from
      * different threads in case the userspace irqchip is used. */
     if (!kvm_irqchip_in_kernel()) {
diff --git a/target/i386/kvm/xen-emu.c b/target/i386/kvm/xen-emu.c
index 821629f..b52617d 100644
--- a/target/i386/kvm/xen-emu.c
+++ b/target/i386/kvm/xen-emu.c
@@ -320,6 +320,39 @@ void *kvm_xen_get_vcpu_info_hva(uint32_t vcpu_id)
     return X86_CPU(cs)->env.xen_vcpu_info_hva;
 }
 
+void kvm_xen_maybe_deassert_callback(CPUState *cs)
+{
+    CPUX86State *env = &X86_CPU(cs)->env;
+    struct vcpu_info *vi = env->xen_vcpu_info_hva;
+    if (!vi) {
+        return;
+    }
+
+    /* If the evtchn_upcall_pending flag is cleared, turn the GSI off. */
+    if (!vi->evtchn_upcall_pending) {
+        qemu_mutex_lock_iothread();
+        /*
+         * Check again now we have the lock, because it may have been
+         * asserted in the interim. And we don't want to take the lock
+         * every time because this is a fast path.
+         */
+        if (!vi->evtchn_upcall_pending) {
+            X86_CPU(cs)->env.xen_callback_asserted = false;
+            xen_evtchn_set_callback_level(0);
+        }
+        qemu_mutex_unlock_iothread();
+    }
+}
+
+void kvm_xen_set_callback_asserted(void)
+{
+    CPUState *cs = qemu_get_cpu(0);
+
+    if (cs) {
+        X86_CPU(cs)->env.xen_callback_asserted = true;
+    }
+}
+
 void kvm_xen_inject_vcpu_callback_vector(uint32_t vcpu_id, int type)
 {
     CPUState *cs = qemu_get_cpu(vcpu_id);
@@ -352,6 +385,13 @@ void kvm_xen_inject_vcpu_callback_vector(uint32_t vcpu_id, int type)
          */
         qemu_cpu_kick(cs);
         break;
+
+    case HVM_PARAM_CALLBACK_TYPE_GSI:
+    case HVM_PARAM_CALLBACK_TYPE_PCI_INTX:
+        if (vcpu_id == 0) {
+            xen_evtchn_set_callback_level(1);
+        }
+        break;
     }
 }
 
diff --git a/target/i386/kvm/xen-emu.h b/target/i386/kvm/xen-emu.h
index 4526056..fe85e0b 100644
--- a/target/i386/kvm/xen-emu.h
+++ b/target/i386/kvm/xen-emu.h
@@ -28,5 +28,6 @@ int kvm_xen_init_vcpu(CPUState *cs);
 int kvm_xen_handle_exit(X86CPU *cpu, struct kvm_xen_exit *exit);
 int kvm_put_xen_state(CPUState *cs);
 int kvm_get_xen_state(CPUState *cs);
+void kvm_xen_maybe_deassert_callback(CPUState *cs);
 
 #endif /* QEMU_I386_KVM_XEN_EMU_H */