spapr_events: add support for dedicated hotplug event source

Hotplug events were previously delivered using an EPOW interrupt
and were queued by linux guests into a circular buffer. For traditional
EPOW events like shutdown/resets, this isn't an issue, but for hotplug
events there are cases where this buffer can be exhausted, resulting
in the loss of hotplug events, resets, etc.

Newer-style hotplug event are delivered using a dedicated event source.
We enable this in supported guests by adding standard an additional
event source in the guest device-tree via /event-sources, and, if
the guest advertises support for the newer-style hotplug events,
using the corresponding interrupt to signal the available of
hotplug/unplug events.

Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
diff --git a/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h
index b6f9f1b..21af971 100644
--- a/include/hw/ppc/spapr.h
+++ b/include/hw/ppc/spapr.h
@@ -13,6 +13,7 @@
 struct sPAPRNVRAM;
 typedef struct sPAPRConfigureConnectorState sPAPRConfigureConnectorState;
 typedef struct sPAPREventLogEntry sPAPREventLogEntry;
+typedef struct sPAPREventSource sPAPREventSource;
 
 #define HPTE64_V_HPTE_DIRTY     0x0000000000000040ULL
 #define SPAPR_ENTRY_POINT       0x100
@@ -77,9 +78,10 @@
     sPAPROptionVector *ov5_cas;     /* negotiated (via CAS) option vectors */
     bool cas_reboot;
 
-    uint32_t check_exception_irq;
     Notifier epow_notifier;
     QTAILQ_HEAD(, sPAPREventLogEntry) pending_events;
+    bool use_hotplug_event_source;
+    sPAPREventSource *event_sources;
 
     /* Migration state */
     int htab_save_index;
@@ -584,7 +586,7 @@
 };
 
 void spapr_events_init(sPAPRMachineState *sm);
-void spapr_dt_events(void *fdt, uint32_t check_exception_irq);
+void spapr_dt_events(sPAPRMachineState *sm, void *fdt);
 int spapr_h_cas_compose_response(sPAPRMachineState *sm,
                                  target_ulong addr, target_ulong size,
                                  bool cpu_update,