[PULL 08/35] plugins: add API for registering discontinuity callbacks

["Alex Bennée" <alex.bennee@linaro.org>]

From: Julian Ganz <neither@nut.email>

The plugin API allows registration of callbacks for a variety of VCPU
related events, such as VCPU reset, idle and resume. In addition to
those events, we recently defined discontinuity events, which include
traps.

This change introduces a function to register callbacks for these
events. We define one distinct plugin event type for each type of
discontinuity, granting fine control to plugins in term of which events
they receive.

Reviewed-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Julian Ganz <neither@nut.email>
Message-ID: <20251027110344.2289945-9-alex.bennee@linaro.org>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>

diff --git a/include/qemu/plugin-event.h b/include/qemu/plugin-event.h
index 7056d8427b7..1100dae2123 100644
--- a/include/qemu/plugin-event.h
+++ b/include/qemu/plugin-event.h
@@ -20,6 +20,9 @@ enum qemu_plugin_event {
     QEMU_PLUGIN_EV_VCPU_SYSCALL_RET,
     QEMU_PLUGIN_EV_FLUSH,
     QEMU_PLUGIN_EV_ATEXIT,
+    QEMU_PLUGIN_EV_VCPU_INTERRUPT,
+    QEMU_PLUGIN_EV_VCPU_EXCEPTION,
+    QEMU_PLUGIN_EV_VCPU_HOSTCALL,
     QEMU_PLUGIN_EV_MAX, /* total number of plugin events we support */
 };
 
diff --git a/include/qemu/qemu-plugin.h b/include/qemu/qemu-plugin.h
index 08bf366e363..60de4fdd3fa 100644
--- a/include/qemu/qemu-plugin.h
+++ b/include/qemu/qemu-plugin.h
@@ -281,6 +281,22 @@ QEMU_PLUGIN_API
 void qemu_plugin_register_vcpu_resume_cb(qemu_plugin_id_t id,
                                          qemu_plugin_vcpu_simple_cb_t cb);
 
+/**
+ * qemu_plugin_register_vcpu_discon_cb() - register a discontinuity callback
+ * @id: plugin ID
+ * @type: types of discontinuities for which to call the callback
+ * @cb: callback function
+ *
+ * The @cb function is called every time a vCPU receives a discontinuity event
+ * of the specified type(s), after the vCPU was prepared to handle the event.
+ * Preparation entails updating the PC, usually to some interrupt handler or
+ * trap vector entry.
+ */
+QEMU_PLUGIN_API
+void qemu_plugin_register_vcpu_discon_cb(qemu_plugin_id_t id,
+                                         enum qemu_plugin_discon_type type,
+                                         qemu_plugin_vcpu_discon_cb_t cb);
+
 /** struct qemu_plugin_tb - Opaque handle for a translation block */
 struct qemu_plugin_tb;
 /** struct qemu_plugin_insn - Opaque handle for a translated instruction */
diff --git a/plugins/core.c b/plugins/core.c
index ead09fd2f1e..40d001d39ad 100644
--- a/plugins/core.c
+++ b/plugins/core.c
@@ -569,6 +569,21 @@ void qemu_plugin_register_vcpu_resume_cb(qemu_plugin_id_t id,
     plugin_register_cb(id, QEMU_PLUGIN_EV_VCPU_RESUME, cb);
 }
 
+void qemu_plugin_register_vcpu_discon_cb(qemu_plugin_id_t id,
+                                         enum qemu_plugin_discon_type type,
+                                         qemu_plugin_vcpu_discon_cb_t cb)
+{
+    if (type & QEMU_PLUGIN_DISCON_INTERRUPT) {
+        plugin_register_cb(id, QEMU_PLUGIN_EV_VCPU_INTERRUPT, cb);
+    }
+    if (type & QEMU_PLUGIN_DISCON_EXCEPTION) {
+        plugin_register_cb(id, QEMU_PLUGIN_EV_VCPU_EXCEPTION, cb);
+    }
+    if (type & QEMU_PLUGIN_DISCON_HOSTCALL) {
+        plugin_register_cb(id, QEMU_PLUGIN_EV_VCPU_HOSTCALL, cb);
+    }
+}
+
 void qemu_plugin_register_flush_cb(qemu_plugin_id_t id,
                                    qemu_plugin_simple_cb_t cb)
 {
-- 
2.47.3