interrupt: Introduce set_ack_and_handler

Add set_ack_and_handler helper to setup ack and handler function of gsi
level interrupt.

Signed-off-by: Asias He <asias@cloudius-systems.com>

arch/x64/ioapic.cc

@@ -84,12 +84,21 @@ gsi_level_interrupt::gsi_level_interrupt(unsigned gsi,
                                          std::function<void ()> handler)
     : _vector(idt.register_level_triggered_handler(gsi, ack, handler))
 {
-    _gsi.set(gsi, _vector);
+    _gsi.set(gsi, _vector.get());
+}
+
+void gsi_level_interrupt::set_ack_and_handler(unsigned gsi,
+        std::function<bool ()> ack,
+        std::function<void ()> handler)
+{
+    _vector = idt.register_level_triggered_handler(gsi, ack, handler);
+    _gsi.set(gsi, _vector.get());
 }
 
 gsi_level_interrupt::~gsi_level_interrupt()
 {
     _gsi.clear();
-    idt.unregister_handler(_vector);
+    if (_vector)
+        idt.unregister_handler(_vector.get());
 }
 

include/osv/interrupt.hh

@@ -17,6 +17,7 @@
 #include "drivers/pci-function.hh"
 #include <osv/types.h>
 #include <initializer_list>
+#include <boost/optional.hpp>
 
 // max vectors per request
 const int max_vectors = 256;
@@ -118,12 +119,17 @@ private:
 
 class gsi_level_interrupt {
 public:
+    gsi_level_interrupt() {};
     gsi_level_interrupt(unsigned gsi,
                         std::function<bool ()> ack,
                         std::function<void ()> handler);
     ~gsi_level_interrupt();
+
+    void set_ack_and_handler(unsigned gsi,
+            std::function<bool ()> ack,
+            std::function<void ()> handler);
 private:
-    unsigned _vector;
+    boost::optional<unsigned> _vector;
     gsi_interrupt _gsi;
 };