[v4,06/18] plugins: define qemu_plugin_u64

Commit Message

Pierrick Bouvier Feb. 13, 2024, 9:39 a.m. UTC

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

Signed-off-by: Pierrick Bouvier <[e-mail]>
---
 include/qemu/qemu-plugin.h   | 52 ++++++++++++++++++++++++++++++++++++
 plugins/api.c                | 33 +++++++++++++++++++++++
 plugins/qemu-plugins.symbols |  4 +++
 3 files changed, 89 insertions(+)

Comments

Richard Henderson Feb. 13, 2024, 6:29 p.m. UTC | #1

On 2/12/24 23:39, Pierrick Bouvier wrote:
> +uint64_t qemu_plugin_u64_sum(qemu_plugin_u64 entry)
> +{
> +    uint64_t total = 0;
> +    for (int i = 0; i < qemu_plugin_num_vcpus(); ++i) {
> +        total += qemu_plugin_u64_get(entry, i);
> +    }

Avoid complex loop bounds whenever possible.

   for (int i = 0, n = qemu_plugin_num_vcpus(); i < n; ++i)

or

   for (int i = qemu_plugin_num_vcpus() - 1; i >= 0; --i)

With that,

Reviewed-by: Richard Henderson <[e-mail]>


r~

Patch

diff --git a/include/qemu/qemu-plugin.h b/include/qemu/qemu-plugin.h
index 0994935d4a2..a48586ef0c1 100644
--- a/include/qemu/qemu-plugin.h
+++ b/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
  *
@@ -785,4 +796,45 @@  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 */
diff --git a/plugins/api.c b/plugins/api.c
index 76fbca685f4..15edad6769b 100644
--- a/plugins/api.c
+++ b/plugins/api.c
@@ -541,3 +541,36 @@  void *qemu_plugin_scoreboard_find(struct qemu_plugin_scoreboard *score,
     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; i < qemu_plugin_num_vcpus(); ++i) {
+        total += qemu_plugin_u64_get(entry, i);
+    }
+    return total;
+}
diff --git a/plugins/qemu-plugins.symbols b/plugins/qemu-plugins.symbols
index 3f93e7d6b13..6204453d0fd 100644
--- a/plugins/qemu-plugins.symbols
+++ b/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;
 };