kvm: Introduce kvm_irqchip_update_msi_route

This service allows to update an MSI route without releasing/reacquiring
the associated VIRQ. Will be used by PCI device assignment, later on
likely also by virtio/vhost and VFIO.
Signed-off-by: NJan Kiszka <jan.kiszka@siemens.com>
Acked-by: NAcked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: NAvi Kivity <avi@redhat.com>

kvm-all.c

@@ -963,6 +963,30 @@ static void kvm_add_routing_entry(KVMState *s,
     kvm_irqchip_commit_routes(s);
 }
 
+static int kvm_update_routing_entry(KVMState *s,
+                                    struct kvm_irq_routing_entry *new_entry)
+{
+    struct kvm_irq_routing_entry *entry;
+    int n;
+
+    for (n = 0; n < s->irq_routes->nr; n++) {
+        entry = &s->irq_routes->entries[n];
+        if (entry->gsi != new_entry->gsi) {
+            continue;
+        }
+
+        entry->type = new_entry->type;
+        entry->flags = new_entry->flags;
+        entry->u = new_entry->u;
+
+        kvm_irqchip_commit_routes(s);
+
+        return 0;
+    }
+
+    return -ESRCH;
+}
+
 void kvm_irqchip_add_irq_route(KVMState *s, int irq, int irqchip, int pin)
 {
     struct kvm_irq_routing_entry e;
@@ -1125,6 +1149,24 @@ int kvm_irqchip_add_msi_route(KVMState *s, MSIMessage msg)
     return virq;
 }
 
+int kvm_irqchip_update_msi_route(KVMState *s, int virq, MSIMessage msg)
+{
+    struct kvm_irq_routing_entry kroute;
+
+    if (!kvm_irqchip_in_kernel()) {
+        return -ENOSYS;
+    }
+
+    kroute.gsi = virq;
+    kroute.type = KVM_IRQ_ROUTING_MSI;
+    kroute.flags = 0;
+    kroute.u.msi.address_lo = (uint32_t)msg.address;
+    kroute.u.msi.address_hi = msg.address >> 32;
+    kroute.u.msi.data = msg.data;
+
+    return kvm_update_routing_entry(s, &kroute);
+}
+
 static int kvm_irqchip_assign_irqfd(KVMState *s, int fd, int virq, bool assign)
 {
     struct kvm_irqfd irqfd = {

kvm.h

@@ -270,6 +270,7 @@ int kvm_set_ioeventfd_mmio(int fd, uint32_t adr, uint32_t val, bool assign,
 int kvm_set_ioeventfd_pio_word(int fd, uint16_t adr, uint16_t val, bool assign);
 
 int kvm_irqchip_add_msi_route(KVMState *s, MSIMessage msg);
+int kvm_irqchip_update_msi_route(KVMState *s, int virq, MSIMessage msg);
 void kvm_irqchip_release_virq(KVMState *s, int virq);
 
 int kvm_irqchip_add_irqfd_notifier(KVMState *s, EventNotifier *n, int virq);