Re: [PATCH 22/33] vhost-user-blk: add some useful trace-points

[Vladimir Sementsov-Ogievskiy]

On 09.10.25 22:07, Raphael Norwitz wrote:

On Wed, Aug 13, 2025 at 1:01 PM Vladimir Sementsov-Ogievskiy
<vsement...@yandex-team.ru> wrote:

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsement...@yandex-team.ru>
---
  hw/block/trace-events     | 10 ++++++++++
  hw/block/vhost-user-blk.c | 15 +++++++++++++++
  2 files changed, 25 insertions(+)

diff --git a/hw/block/trace-events b/hw/block/trace-events
index cc9a9f2460..3b5fd2a599 100644
--- a/hw/block/trace-events
+++ b/hw/block/trace-events
@@ -58,6 +58,16 @@ virtio_blk_handle_zone_mgmt(void *vdev, void *req, uint8_t 
op, int64_t sector, i
  virtio_blk_handle_zone_reset_all(void *vdev, void *req, int64_t sector, int64_t len) "vdev %p req %p 
sector 0x%" PRIx64 " cap 0x%" PRIx64 ""
  virtio_blk_handle_zone_append(void *vdev, void *req, int64_t sector) "vdev %p req %p, append 
sector 0x%" PRIx64 ""

+# vhost-user-blk.c
+vhost_user_blk_start(void) ""
+vhost_user_blk_start_finish(void) ""
+vhost_user_blk_stop(void) ""
+vhost_user_blk_stop_finish(void) ""
+vhost_user_blk_connect(void) ""
+vhost_user_blk_connect_finish(void) ""
+vhost_user_blk_device_realize(void) ""
+vhost_user_blk_device_realize_finish(void) ""

Should we also trace the VirtIODevice/vdev pointer like in virtio-blk.c?

Agree, it may help to debug a setup with several disk, and just for consistency 
with virtio-blk.c

+
  # hd-geometry.c
  hd_geometry_lchs_guess(void *blk, int cyls, int heads, int secs) "blk %p LCHS %d 
%d %d"
  hd_geometry_guess(void *blk, uint32_t cyls, uint32_t heads, uint32_t secs, int trans) 
"blk %p CHS %u %u %u trans %d"
diff --git a/hw/block/vhost-user-blk.c b/hw/block/vhost-user-blk.c
index de7a810c93..c8bc2c78e6 100644
--- a/hw/block/vhost-user-blk.c
+++ b/hw/block/vhost-user-blk.c
@@ -31,6 +31,7 @@
  #include "hw/virtio/virtio-access.h"
  #include "system/system.h"
  #include "system/runstate.h"
+#include "trace.h"

  static const int user_feature_bits[] = {
      VIRTIO_BLK_F_SIZE_MAX,
@@ -137,6 +138,8 @@ static int vhost_user_blk_start(VirtIODevice *vdev, Error 
**errp)
      VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
      int i, ret;

+    trace_vhost_user_blk_start();
+
      if (!k->set_guest_notifiers) {
          error_setg(errp, "binding does not support guest notifiers");
          return -ENOSYS;
@@ -192,6 +195,8 @@ static int vhost_user_blk_start(VirtIODevice *vdev, Error 
**errp)
      }
      s->started_vu = true;

+    trace_vhost_user_blk_start_finish();
+
      return ret;

  err_guest_notifiers:
@@ -212,6 +217,8 @@ static int vhost_user_blk_stop(VirtIODevice *vdev)
      int ret;
      bool force_stop = false;

+    trace_vhost_user_blk_stop();
+
      if (!s->started_vu) {
          return 0;
      }
@@ -233,6 +240,8 @@ static int vhost_user_blk_stop(VirtIODevice *vdev)
      }

      vhost_dev_disable_notifiers(&s->dev, vdev);
+
+    trace_vhost_user_blk_stop_finish();
      return ret;
  }

@@ -340,6 +349,8 @@ static int vhost_user_blk_connect(DeviceState *dev, Error 
**errp)
      VHostUserBlk *s = VHOST_USER_BLK(vdev);
      int ret = 0;

+    trace_vhost_user_blk_connect();
+
      if (s->connected) {
          return 0;
      }
@@ -365,6 +376,7 @@ static int vhost_user_blk_connect(DeviceState *dev, Error 
**errp)
          ret = vhost_user_blk_start(vdev, errp);
      }

+    trace_vhost_user_blk_connect_finish();
      return ret;
  }

@@ -455,6 +467,8 @@ static void vhost_user_blk_device_realize(DeviceState *dev, 
Error **errp)
      int retries;
      int i, ret;

+    trace_vhost_user_blk_device_realize();
+
      if (!s->chardev.chr) {
          error_setg(errp, "chardev is mandatory");
          return;
@@ -514,6 +528,7 @@ static void vhost_user_blk_device_realize(DeviceState *dev, 
Error **errp)
      qemu_chr_fe_set_handlers(&s->chardev,  NULL, NULL,
                               vhost_user_blk_event, NULL, (void *)dev,
                               NULL, true);
+    trace_vhost_user_blk_device_realize_finish();
      return;

  virtio_err:
--
2.48.1

--
Best regards,
Vladimir