ehci: fix Interrupt Threshold Control implementation

First, not all interrupts are subject to Interrupt Threshold Control,
some of them must be delivered without delay.

Second, Interrupt Threshold Control state must be part of vmstate,
otherwise we might loose IRQs on migration.
Signed-off-by: NGerd Hoffmann <kraxel@redhat.com>

hw/usb/hcd-ehci.c

@@ -575,7 +575,12 @@ static inline void ehci_update_irq(EHCIState *s)
 /* flag interrupt condition */
 static inline void ehci_raise_irq(EHCIState *s, int intr)
 {
+    if (intr & (USBSTS_PCD | USBSTS_FLR | USBSTS_HSE)) {
+        s->usbsts |= intr;
+        ehci_update_irq(s);
+    } else {
         s->usbsts_pending |= intr;
+    }
 }
 
 /*
@@ -2466,13 +2471,16 @@ static int usb_ehci_post_load(void *opaque, int version_id)
 
 static const VMStateDescription vmstate_ehci = {
     .name        = "ehci",
-    .version_id  = 1,
+    .version_id  = 2,
+    .minimum_version_id  = 1,
     .post_load   = usb_ehci_post_load,
     .fields      = (VMStateField[]) {
         VMSTATE_PCI_DEVICE(dev, EHCIState),
         /* mmio registers */
         VMSTATE_UINT32(usbcmd, EHCIState),
         VMSTATE_UINT32(usbsts, EHCIState),
+        VMSTATE_UINT32_V(usbsts_pending, EHCIState, 2),
+        VMSTATE_UINT32_V(usbsts_frindex, EHCIState, 2),
         VMSTATE_UINT32(usbintr, EHCIState),
         VMSTATE_UINT32(frindex, EHCIState),
         VMSTATE_UINT32(ctrldssegment, EHCIState),