[RFC PATCH 7/8] plugins: add time control API

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

Expose the ability to control time through the plugin API. Only one
plugin can control time so it has to request control when loaded.
There are probably more corner cases to catch here.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
---
 include/qemu/qemu-plugin.h   | 19 +++++++++++++++++++
 plugins/api.c                | 22 ++++++++++++++++++++++
 plugins/qemu-plugins.symbols |  2 ++
 3 files changed, 43 insertions(+)

diff --git a/include/qemu/qemu-plugin.h b/include/qemu/qemu-plugin.h
index 50a9957279..8385670976 100644
--- a/include/qemu/qemu-plugin.h
+++ b/include/qemu/qemu-plugin.h
@@ -536,7 +536,26 @@ void qemu_plugin_register_vcpu_mem_inline(struct qemu_plugin_insn *insn,
                                           enum qemu_plugin_op op, void *ptr,
                                           uint64_t imm);
 
+/**
+ * qemu_plugin_request_time_control() - request the ability to control time
+ *
+ * This grants the plugin the ability to control system time. Only one
+ * plugin can control time so if multiple plugins request the ability
+ * all but the first will fail.
+ *
+ * Returns an opaque handle or NULL if fails
+ */
+const void * qemu_plugin_request_time_control(void);
 
+/**
+ * qemu_plugin_update_ns() - update system emulation time
+ * @handle: opaque handle returned by qemu_plugin_request_time_control()
+ * @time: time in nanoseconds
+ *
+ * This allows an appropriately authorised plugin (i.e. holding the
+ * time control handle) to move system time forward to @time.
+ */
+void qemu_plugin_update_ns(const void *handle, int64_t new_time);
 
 typedef void
 (*qemu_plugin_vcpu_syscall_cb_t)(qemu_plugin_id_t id, unsigned int vcpu_index,
diff --git a/plugins/api.c b/plugins/api.c
index 2078b16edb..8402b3a5f6 100644
--- a/plugins/api.c
+++ b/plugins/api.c
@@ -37,6 +37,7 @@
 #include "qemu/osdep.h"
 #include "qemu/plugin.h"
 #include "qemu/log.h"
+#include "qemu/timer.h"
 #include "tcg/tcg.h"
 #include "exec/exec-all.h"
 #include "exec/ram_addr.h"
@@ -442,3 +443,24 @@ uint64_t qemu_plugin_entry_code(void)
 #endif
     return entry;
 }
+
+/*
+ * Time control
+ */
+static bool has_control;
+
+const void * qemu_plugin_request_time_control(void)
+{
+    if (!has_control) {
+        has_control = true;
+        return &has_control;
+    }
+    return NULL;
+}
+
+void qemu_plugin_update_ns(const void *handle, int64_t new_time)
+{
+    if (handle == &has_control) {
+        qemu_clock_advance_virtual_time(new_time);
+    }
+}
diff --git a/plugins/qemu-plugins.symbols b/plugins/qemu-plugins.symbols
index 71f6c90549..91b882fecc 100644
--- a/plugins/qemu-plugins.symbols
+++ b/plugins/qemu-plugins.symbols
@@ -35,11 +35,13 @@
   qemu_plugin_register_vcpu_tb_exec_cb;
   qemu_plugin_register_vcpu_tb_exec_inline;
   qemu_plugin_register_vcpu_tb_trans_cb;
+  qemu_plugin_request_time_control;
   qemu_plugin_reset;
   qemu_plugin_start_code;
   qemu_plugin_tb_get_insn;
   qemu_plugin_tb_n_insns;
   qemu_plugin_tb_vaddr;
   qemu_plugin_uninstall;
+  qemu_plugin_update_ns;
   qemu_plugin_vcpu_for_each;
 };
-- 
2.39.2