plugins: define qemu_plugin_u64

Additionally to the scoreboard, we define a qemu_plugin_u64, which is a
simple struct holding a pointer to a scoreboard, and a given offset.
This allows to have a scoreboard containing structs, without having to
bring offset to operate on a specific field.

Since most of the plugins are simply collecting a sum of per-cpu values,
qemu_plugin_u64 directly support this operation as well.

All inline operations defined later will use a qemu_plugin_u64 as input.

New functions:
- qemu_plugin_u64_add
- qemu_plugin_u64_get
- qemu_plugin_u64_set
- qemu_plugin_u64_sum
New macros:
- qemu_plugin_scoreboard_u64
- qemu_plugin_scoreboard_u64_in_struct

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>
Message-Id: <20240304130036.124418-3-pierrick.bouvier@linaro.org>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20240305121005.3528075-16-alex.bennee@linaro.org>

plugins/api.c

@@ -484,3 +484,37 @@ void *qemu_plugin_scoreboard_find(struct qemu_plugin_scoreboard *score,
     char *base_ptr = score->data->data;
     return base_ptr + vcpu_index * g_array_get_element_size(score->data);
 }
+
+static uint64_t *plugin_u64_address(qemu_plugin_u64 entry,
+                                    unsigned int vcpu_index)
+{
+    char *ptr = qemu_plugin_scoreboard_find(entry.score, vcpu_index);
+    return (uint64_t *)(ptr + entry.offset);
+}
+
+void qemu_plugin_u64_add(qemu_plugin_u64 entry, unsigned int vcpu_index,
+                         uint64_t added)
+{
+    *plugin_u64_address(entry, vcpu_index) += added;
+}
+
+uint64_t qemu_plugin_u64_get(qemu_plugin_u64 entry,
+                             unsigned int vcpu_index)
+{
+    return *plugin_u64_address(entry, vcpu_index);
+}
+
+void qemu_plugin_u64_set(qemu_plugin_u64 entry, unsigned int vcpu_index,
+                         uint64_t val)
+{
+    *plugin_u64_address(entry, vcpu_index) = val;
+}
+
+uint64_t qemu_plugin_u64_sum(qemu_plugin_u64 entry)
+{
+    uint64_t total = 0;
+    for (int i = 0, n = qemu_plugin_num_vcpus(); i < n; ++i) {
+        total += qemu_plugin_u64_get(entry, i);
+    }
+    return total;
+}