Hi Maciej,

On 27/08/2024 20:54, Maciej S. Szmigiero wrote:
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From: "Maciej S. Szmigiero" <maciej.szmigi...@oracle.com>

This way both the start and end points of migrating a particular VFIO
device are known.

Add also a vfio_save_iterate_empty_hit trace event so it is known when
there's no more data to send for that device.

Out of curiosity, what are these traces used for?


Signed-off-by: Maciej S. Szmigiero <maciej.szmigi...@oracle.com>
---
  hw/vfio/migration.c           | 13 +++++++++++++
  hw/vfio/trace-events          |  3 +++
  include/hw/vfio/vfio-common.h |  3 +++
  3 files changed, 19 insertions(+)

diff --git a/hw/vfio/migration.c b/hw/vfio/migration.c
index 262d42a46e58..24679d8c5034 100644
--- a/hw/vfio/migration.c
+++ b/hw/vfio/migration.c
@@ -472,6 +472,9 @@ static int vfio_save_setup(QEMUFile *f, void *opaque, Error 
**errp)
          return -ENOMEM;
      }

+    migration->save_iterate_run = false;
+    migration->save_iterate_empty_hit = false;
+
      if (vfio_precopy_supported(vbasedev)) {
          switch (migration->device_state) {
          case VFIO_DEVICE_STATE_RUNNING:
@@ -605,9 +608,17 @@ static int vfio_save_iterate(QEMUFile *f, void *opaque)
      VFIOMigration *migration = vbasedev->migration;
      ssize_t data_size;

+    if (!migration->save_iterate_run) {
+        trace_vfio_save_iterate_started(vbasedev->name);
+        migration->save_iterate_run = true;

Maybe rename save_iterate_run to save_iterate_started so it's aligned with trace_vfio_save_iterate_started and trace_vfio_save_complete_precopy_started?

+    }
+
      data_size = vfio_save_block(f, migration);
      if (data_size < 0) {
          return data_size;
+    } else if (data_size == 0 && !migration->save_iterate_empty_hit) {
+        trace_vfio_save_iterate_empty_hit(vbasedev->name);
+        migration->save_iterate_empty_hit = true;

During precopy we could hit empty multiple times. Any reason why only the first time should be traced?

      }

      vfio_update_estimated_pending_data(migration, data_size);
@@ -633,6 +644,8 @@ static int vfio_save_complete_precopy(QEMUFile *f, void 
*opaque)
      int ret;
      Error *local_err = NULL;

+    trace_vfio_save_complete_precopy_started(vbasedev->name);
+
      /* We reach here with device state STOP or STOP_COPY only */
      ret = vfio_migration_set_state(vbasedev, VFIO_DEVICE_STATE_STOP_COPY,
                                     VFIO_DEVICE_STATE_STOP, &local_err);
diff --git a/hw/vfio/trace-events b/hw/vfio/trace-events
index 98bd4dcceadc..013c602f30fa 100644
--- a/hw/vfio/trace-events
+++ b/hw/vfio/trace-events
@@ -159,8 +159,11 @@ vfio_migration_state_notifier(const char *name, int state) " 
(%s) state %d"
  vfio_save_block(const char *name, int data_size) " (%s) data_size %d"
  vfio_save_cleanup(const char *name) " (%s)"
  vfio_save_complete_precopy(const char *name, int ret) " (%s) ret %d"
+vfio_save_complete_precopy_started(const char *name) " (%s)"
  vfio_save_device_config_state(const char *name) " (%s)"
  vfio_save_iterate(const char *name, uint64_t precopy_init_size, uint64_t precopy_dirty_size) 
" (%s) precopy initial size 0x%"PRIx64" precopy dirty size 0x%"PRIx64
+vfio_save_iterate_started(const char *name) " (%s)"
+vfio_save_iterate_empty_hit(const char *name) " (%s)"

Let's keep it sorted in alphabetical order.

Thanks.

  vfio_save_setup(const char *name, uint64_t data_buffer_size) " (%s) data buffer 
size 0x%"PRIx64
  vfio_state_pending_estimate(const char *name, uint64_t precopy, uint64_t postcopy, uint64_t precopy_init_size, 
uint64_t precopy_dirty_size) " (%s) precopy 0x%"PRIx64" postcopy 0x%"PRIx64" precopy initial 
size 0x%"PRIx64" precopy dirty size 0x%"PRIx64
  vfio_state_pending_exact(const char *name, uint64_t precopy, uint64_t postcopy, uint64_t stopcopy_size, uint64_t 
precopy_init_size, uint64_t precopy_dirty_size) " (%s) precopy 0x%"PRIx64" postcopy 0x%"PRIx64" stopcopy 
size 0x%"PRIx64" precopy initial size 0x%"PRIx64" precopy dirty size 0x%"PRIx64
diff --git a/include/hw/vfio/vfio-common.h b/include/hw/vfio/vfio-common.h
index fed499b199f0..32d58e3e025b 100644
--- a/include/hw/vfio/vfio-common.h
+++ b/include/hw/vfio/vfio-common.h
@@ -73,6 +73,9 @@ typedef struct VFIOMigration {
      uint64_t precopy_init_size;
      uint64_t precopy_dirty_size;
      bool initial_data_sent;
+
+    bool save_iterate_run;
+    bool save_iterate_empty_hit;
  } VFIOMigration;

  struct VFIOGroup;

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