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>

include/qemu/qemu-plugin.h

@@ -225,6 +225,17 @@ struct qemu_plugin_insn;
 /** struct qemu_plugin_scoreboard - Opaque handle for a scoreboard */
 struct qemu_plugin_scoreboard;
 
+/**
+ * typedef qemu_plugin_u64 - uint64_t member of an entry in a scoreboard
+ *
+ * This field allows to access a specific uint64_t member in one given entry,
+ * located at a specified offset. Inline operations expect this as entry.
+ */
+typedef struct {
+    struct qemu_plugin_scoreboard *score;
+    size_t offset;
+} qemu_plugin_u64;
+
 /**
  * enum qemu_plugin_cb_flags - type of callback
  *
@@ -784,4 +795,45 @@ QEMU_PLUGIN_API
 void *qemu_plugin_scoreboard_find(struct qemu_plugin_scoreboard *score,
                                   unsigned int vcpu_index);
 
+/* Macros to define a qemu_plugin_u64 */
+#define qemu_plugin_scoreboard_u64(score) \
+    (qemu_plugin_u64) {score, 0}
+#define qemu_plugin_scoreboard_u64_in_struct(score, type, member) \
+    (qemu_plugin_u64) {score, offsetof(type, member)}
+
+/**
+ * qemu_plugin_u64_add() - add a value to a qemu_plugin_u64 for a given vcpu
+ * @entry: entry to query
+ * @vcpu_index: entry index
+ * @added: value to add
+ */
+QEMU_PLUGIN_API
+void qemu_plugin_u64_add(qemu_plugin_u64 entry, unsigned int vcpu_index,
+                         uint64_t added);
+
+/**
+ * qemu_plugin_u64_get() - get value of a qemu_plugin_u64 for a given vcpu
+ * @entry: entry to query
+ * @vcpu_index: entry index
+ */
+QEMU_PLUGIN_API
+uint64_t qemu_plugin_u64_get(qemu_plugin_u64 entry, unsigned int vcpu_index);
+
+/**
+ * qemu_plugin_u64_set() - set value of a qemu_plugin_u64 for a given vcpu
+ * @entry: entry to query
+ * @vcpu_index: entry index
+ * @val: new value
+ */
+QEMU_PLUGIN_API
+void qemu_plugin_u64_set(qemu_plugin_u64 entry, unsigned int vcpu_index,
+                         uint64_t val);
+
+/**
+ * qemu_plugin_u64_sum() - return sum of all vcpu entries in a scoreboard
+ * @entry: entry to sum
+ */
+QEMU_PLUGIN_API
+uint64_t qemu_plugin_u64_sum(qemu_plugin_u64 entry);
+
 #endif /* QEMU_QEMU_PLUGIN_H */

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;
+}

plugins/qemu-plugins.symbols

@@ -44,6 +44,10 @@
   qemu_plugin_tb_get_insn;
   qemu_plugin_tb_n_insns;
   qemu_plugin_tb_vaddr;
+  qemu_plugin_u64_add;
+  qemu_plugin_u64_get;
+  qemu_plugin_u64_set;
+  qemu_plugin_u64_sum;
   qemu_plugin_uninstall;
   qemu_plugin_vcpu_for_each;
 };