On 2025/07/21 20:29, Arun Menon wrote:
This is an incremental step in converting vmstate loading
code to report error via Error objects instead of directly
printing it to console/monitor.
It is ensured that vmstate_load_state() must report an error
in errp, in case of failure.

Signed-off-by: Arun Menon <arme...@redhat.com>
---
  hw/display/virtio-gpu.c     |  2 +-
  hw/pci/pci.c                |  2 +-
  hw/s390x/virtio-ccw.c       |  2 +-
  hw/scsi/spapr_vscsi.c       |  2 +-
  hw/vfio/pci.c               |  2 +-
  hw/virtio/virtio-mmio.c     |  2 +-
  hw/virtio/virtio-pci.c      |  2 +-
  hw/virtio/virtio.c          |  4 ++--
  include/migration/vmstate.h |  2 +-
  migration/cpr.c             |  4 ++--
  migration/savevm.c          |  6 ++++--
  migration/vmstate-types.c   | 10 +++++-----
  migration/vmstate.c         | 45 ++++++++++++++++++++++++++++-----------------
  tests/unit/test-vmstate.c   | 18 +++++++++---------
  ui/vdagent.c                |  2 +-
  15 files changed, 59 insertions(+), 46 deletions(-)

diff --git a/hw/display/virtio-gpu.c b/hw/display/virtio-gpu.c
index 
0a1a625b0ea6cf26cb0d799171a57ed3d3ab2442..5d2ca8d8b864350133a674802d7316abd379591c
 100644
--- a/hw/display/virtio-gpu.c
+++ b/hw/display/virtio-gpu.c
@@ -1343,7 +1343,7 @@ static int virtio_gpu_load(QEMUFile *f, void *opaque, 
size_t size,
      }
/* load & apply scanout state */
-    vmstate_load_state(f, &vmstate_virtio_gpu_scanouts, g, 1);
+    vmstate_load_state(f, &vmstate_virtio_gpu_scanouts, g, 1, NULL);
return 0;
  }
diff --git a/hw/pci/pci.c b/hw/pci/pci.c
index 
c70b5ceebaf1f2b10768bd030526cbb518da2b8d..2ab5d30bb3c319ac1c7bfc9a2acf6a2b38082066
 100644
--- a/hw/pci/pci.c
+++ b/hw/pci/pci.c
@@ -934,7 +934,7 @@ void pci_device_save(PCIDevice *s, QEMUFile *f)
  int pci_device_load(PCIDevice *s, QEMUFile *f)
  {
      int ret;
-    ret = vmstate_load_state(f, &vmstate_pci_device, s, s->version_id);
+    ret = vmstate_load_state(f, &vmstate_pci_device, s, s->version_id, NULL);
      /* Restore the interrupt status bit. */
      pci_update_irq_status(s);
      return ret;
diff --git a/hw/s390x/virtio-ccw.c b/hw/s390x/virtio-ccw.c
index 
d2f85b39f30f7fc82e0c600144c0a958e1269b2c..2f6feff2b0a22d7d7f6aecfd7e7870d8362f1a73
 100644
--- a/hw/s390x/virtio-ccw.c
+++ b/hw/s390x/virtio-ccw.c
@@ -1136,7 +1136,7 @@ static void virtio_ccw_save_config(DeviceState *d, 
QEMUFile *f)
  static int virtio_ccw_load_config(DeviceState *d, QEMUFile *f)
  {
      VirtioCcwDevice *dev = VIRTIO_CCW_DEVICE(d);
-    return vmstate_load_state(f, &vmstate_virtio_ccw_dev, dev, 1);
+    return vmstate_load_state(f, &vmstate_virtio_ccw_dev, dev, 1, NULL);
  }
static void virtio_ccw_pre_plugged(DeviceState *d, Error **errp)
diff --git a/hw/scsi/spapr_vscsi.c b/hw/scsi/spapr_vscsi.c
index 
20f70fb2729de78b9636a6b8c869695dab4f8902..573fdea668536b464bca11f001e9e0288e781493
 100644
--- a/hw/scsi/spapr_vscsi.c
+++ b/hw/scsi/spapr_vscsi.c
@@ -648,7 +648,7 @@ static void *vscsi_load_request(QEMUFile *f, SCSIRequest 
*sreq)
      assert(!req->active);
memset(req, 0, sizeof(*req));
-    rc = vmstate_load_state(f, &vmstate_spapr_vscsi_req, req, 1);
+    rc = vmstate_load_state(f, &vmstate_spapr_vscsi_req, req, 1, NULL);
      if (rc) {
          fprintf(stderr, "VSCSI: failed loading request tag#%u\n", sreq->tag);
          return NULL;
diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c
index 
be05002b9819fafa45cf2fb4d2a0acdc475c558c..f8ce4a40dbe4c070a0d6c111051051ee97542719
 100644
--- a/hw/vfio/pci.c
+++ b/hw/vfio/pci.c
@@ -2797,7 +2797,7 @@ static int vfio_pci_load_config(VFIODevice *vbasedev, 
QEMUFile *f)
          old_addr[bar] = pdev->io_regions[bar].addr;
      }
- ret = vmstate_load_state(f, &vmstate_vfio_pci_config, vdev, 1);
+    ret = vmstate_load_state(f, &vmstate_vfio_pci_config, vdev, 1, NULL);
      if (ret) {
          return ret;
      }
diff --git a/hw/virtio/virtio-mmio.c b/hw/virtio/virtio-mmio.c
index 
532c67107ba1d2978a76cf49f9cdc1de1dea3e11..9058b1563462d4464dcba799643a583c93fb5683
 100644
--- a/hw/virtio/virtio-mmio.c
+++ b/hw/virtio/virtio-mmio.c
@@ -619,7 +619,7 @@ static int virtio_mmio_load_extra_state(DeviceState 
*opaque, QEMUFile *f)
  {
      VirtIOMMIOProxy *proxy = VIRTIO_MMIO(opaque);
- return vmstate_load_state(f, &vmstate_virtio_mmio, proxy, 1);
+    return vmstate_load_state(f, &vmstate_virtio_mmio, proxy, 1, NULL);
  }
static bool virtio_mmio_has_extra_state(DeviceState *opaque)
diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
index 
767216d795998708f5716a23ae16c79cd90ff489..f8b52a611e56c22d844fd4cae3619da4f2686d03
 100644
--- a/hw/virtio/virtio-pci.c
+++ b/hw/virtio/virtio-pci.c
@@ -161,7 +161,7 @@ static int virtio_pci_load_extra_state(DeviceState *d, 
QEMUFile *f)
  {
      VirtIOPCIProxy *proxy = to_virtio_pci_proxy(d);
- return vmstate_load_state(f, &vmstate_virtio_pci, proxy, 1);
+    return vmstate_load_state(f, &vmstate_virtio_pci, proxy, 1, NULL);
  }
static void virtio_pci_save_queue(DeviceState *d, int n, QEMUFile *f)
diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index 
2ab1d20769495ea39445b87e3673b076ad172510..d5698b062a1e95437f6113f41136e90ae06f1974
 100644
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -3317,14 +3317,14 @@ virtio_load(VirtIODevice *vdev, QEMUFile *f, int 
version_id)
      }
if (vdc->vmsd) {
-        ret = vmstate_load_state(f, vdc->vmsd, vdev, version_id);
+        ret = vmstate_load_state(f, vdc->vmsd, vdev, version_id, NULL);
          if (ret) {
              return ret;
          }
      }
/* Subsections */
-    ret = vmstate_load_state(f, &vmstate_virtio, vdev, 1);
+    ret = vmstate_load_state(f, &vmstate_virtio, vdev, 1, NULL);
      if (ret) {
          return ret;
      }
diff --git a/include/migration/vmstate.h b/include/migration/vmstate.h
index 
1ff7bd9ac425ba67cd5ca7ad97bcf570f9e19abe..056781b1c21e737583f081594d9f88b32adfd674
 100644
--- a/include/migration/vmstate.h
+++ b/include/migration/vmstate.h
@@ -1196,7 +1196,7 @@ extern const VMStateInfo vmstate_info_qlist;
      }
int vmstate_load_state(QEMUFile *f, const VMStateDescription *vmsd,
-                       void *opaque, int version_id);
+                       void *opaque, int version_id, Error **errp);
  int vmstate_save_state(QEMUFile *f, const VMStateDescription *vmsd,
                         void *opaque, JSONWriter *vmdesc);
  int vmstate_save_state_with_err(QEMUFile *f, const VMStateDescription *vmsd,
diff --git a/migration/cpr.c b/migration/cpr.c
index 
42ad0b0d500e5de57faf0c6517e216b2d1c0cacf..74fac9521717ec568d14dabcbcb574b19fc1da67
 100644
--- a/migration/cpr.c
+++ b/migration/cpr.c
@@ -233,9 +233,9 @@ int cpr_state_load(MigrationChannel *channel, Error **errp)
          return -ENOTSUP;
      }
- ret = vmstate_load_state(f, &vmstate_cpr_state, &cpr_state, 1);
+    ret = vmstate_load_state(f, &vmstate_cpr_state, &cpr_state, 1, errp);
      if (ret) {
-        error_setg(errp, "vmstate_load_state error %d", ret);
+        error_prepend(errp, "vmstate_load_state error %d ", ret);
          qemu_fclose(f);
          return ret;
      }
diff --git a/migration/savevm.c b/migration/savevm.c
index 
fabbeb296ae987d0c06ba6dafda63720205fecfd..ab947620f724874f325fb9fb59bef50b7c16fb51
 100644
--- a/migration/savevm.c
+++ b/migration/savevm.c
@@ -969,7 +969,8 @@ static int vmstate_load(QEMUFile *f, SaveStateEntry *se)
      if (!se->vmsd) {         /* Old style */
          return se->ops->load_state(f, se->opaque, se->load_version_id);
      }
-    return vmstate_load_state(f, se->vmsd, se->opaque, se->load_version_id);
+    return vmstate_load_state(f, se->vmsd, se->opaque, se->load_version_id,
+                              NULL);
  }
static void vmstate_save_old_style(QEMUFile *f, SaveStateEntry *se,
@@ -2839,7 +2840,8 @@ static int qemu_loadvm_state_header(QEMUFile *f)
              error_report("Configuration section missing");
              return -EINVAL;
          }
-        ret = vmstate_load_state(f, &vmstate_configuration, &savevm_state, 0);
+        ret = vmstate_load_state(f, &vmstate_configuration, &savevm_state, 0,
+                                 NULL);
if (ret) {
              return ret;
diff --git a/migration/vmstate-types.c b/migration/vmstate-types.c
index 
741a588b7e18c6d37724b08a0101edc8bc74a0a5..1c5b76e1dd198030847971bc35637867c9d54fc0
 100644
--- a/migration/vmstate-types.c
+++ b/migration/vmstate-types.c
@@ -549,7 +549,7 @@ static int get_tmp(QEMUFile *f, void *pv, size_t size,
/* Writes the parent field which is at the start of the tmp */
      *(void **)tmp = pv;
-    ret = vmstate_load_state(f, vmsd, tmp, version_id);
+    ret = vmstate_load_state(f, vmsd, tmp, version_id, NULL);
      g_free(tmp);
      return ret;
  }
@@ -649,7 +649,7 @@ static int get_qtailq(QEMUFile *f, void *pv, size_t 
unused_size,
while (qemu_get_byte(f)) {
          elm = g_malloc(size);
-        ret = vmstate_load_state(f, vmsd, elm, version_id);
+        ret = vmstate_load_state(f, vmsd, elm, version_id, NULL);
          if (ret) {
              return ret;
          }
@@ -803,7 +803,7 @@ static int get_gtree(QEMUFile *f, void *pv, size_t 
unused_size,
              key = (void *)(uintptr_t)qemu_get_be64(f);
          } else {
              key = g_malloc0(key_size);
-            ret = vmstate_load_state(f, key_vmsd, key, version_id);
+            ret = vmstate_load_state(f, key_vmsd, key, version_id, NULL);
              if (ret) {
                  error_report("%s : failed to load %s (%d)",
                               field->name, key_vmsd->name, ret);
@@ -811,7 +811,7 @@ static int get_gtree(QEMUFile *f, void *pv, size_t 
unused_size,
              }
          }
          val = g_malloc0(val_size);
-        ret = vmstate_load_state(f, val_vmsd, val, version_id);
+        ret = vmstate_load_state(f, val_vmsd, val, version_id, NULL);
          if (ret) {
              error_report("%s : failed to load %s (%d)",
                           field->name, val_vmsd->name, ret);
@@ -892,7 +892,7 @@ static int get_qlist(QEMUFile *f, void *pv, size_t 
unused_size,
while (qemu_get_byte(f)) {
          elm = g_malloc(size);
-        ret = vmstate_load_state(f, vmsd, elm, version_id);
+        ret = vmstate_load_state(f, vmsd, elm, version_id, NULL);
          if (ret) {
              error_report("%s: failed to load %s (%d)", field->name,
                           vmsd->name, ret);
diff --git a/migration/vmstate.c b/migration/vmstate.c
index 
129b19d7603a0ddf8ab6e946e41c1c4d773d1fa8..288b57e1ed778cce21247b64d5e97dfef41ad586
 100644
--- a/migration/vmstate.c
+++ b/migration/vmstate.c
@@ -132,29 +132,33 @@ static void vmstate_handle_alloc(void *ptr, const 
VMStateField *field,
  }
int vmstate_load_state(QEMUFile *f, const VMStateDescription *vmsd,
-                       void *opaque, int version_id)
+                       void *opaque, int version_id, Error **errp)
  {
      const VMStateField *field = vmsd->fields;
      int ret = 0;
trace_vmstate_load_state(vmsd->name, version_id);
      if (version_id > vmsd->version_id) {
-        error_report("%s: incoming version_id %d is too new "
-                     "for local version_id %d",
-                     vmsd->name, version_id, vmsd->version_id);
+        error_setg(errp, "%s: incoming version_id %d is too new "
+                   "for local version_id %d",
+                   vmsd->name, version_id, vmsd->version_id);
          trace_vmstate_load_state_end(vmsd->name, "too new", -EINVAL);
          return -EINVAL;
      }
      if  (version_id < vmsd->minimum_version_id) {
-        error_report("%s: incoming version_id %d is too old "
-                     "for local minimum version_id  %d",
-                     vmsd->name, version_id, vmsd->minimum_version_id);
+        error_setg(errp, "%s: incoming version_id %d is too old "
+                   "for local minimum version_id  %d",
+                   vmsd->name, version_id, vmsd->minimum_version_id);
          trace_vmstate_load_state_end(vmsd->name, "too old", -EINVAL);
          return -EINVAL;
      }
      if (vmsd->pre_load) {
          ret = vmsd->pre_load(opaque);
          if (ret) {
+            error_setg(errp, "VM pre load failed for: '%s', "
+                       "version_id: '%d', minimum version_id: '%d', ret: %d",
+                       vmsd->name, vmsd->version_id, vmsd->minimum_version_id,
+                       ret);
              return ret;
          }
      }
@@ -192,10 +196,12 @@ int vmstate_load_state(QEMUFile *f, const 
VMStateDescription *vmsd,
if (inner_field->flags & VMS_STRUCT) {
                      ret = vmstate_load_state(f, inner_field->vmsd, curr_elem,
-                                             inner_field->vmsd->version_id);
+                                             inner_field->vmsd->version_id,
+                                             errp);
                  } else if (inner_field->flags & VMS_VSTRUCT) {
                      ret = vmstate_load_state(f, inner_field->vmsd, curr_elem,
-                                             inner_field->struct_version_id);
+                                             inner_field->struct_version_id,
+                                             errp);
                  } else {
                      ret = inner_field->info->get(f, curr_elem, size,
                                                   inner_field);
@@ -211,27 +217,32 @@ int vmstate_load_state(QEMUFile *f, const 
VMStateDescription *vmsd,
                  }
                  if (ret < 0) {
                      qemu_file_set_error(f, ret);
-                    error_report("Failed to load %s:%s", vmsd->name,
-                                 field->name);
+                    error_prepend(errp, "Failed to load %s:%s version_id: %d ",
+                                  vmsd->name, field->name, vmsd->version_id);
                      trace_vmstate_load_field_error(field->name, ret);
                      return ret;
                  }
              }
          } else if (field->flags & VMS_MUST_EXIST) {
-            error_report("Input validation failed: %s/%s",
-                         vmsd->name, field->name);
+            error_setg(errp, "Input validation failed: %s/%s version_id: %d",
+                       vmsd->name, field->name, vmsd->version_id);
              return -1;
          }
          field++;
      }
      assert(field->flags == VMS_END);
-    ret = vmstate_subsection_load(f, vmsd, opaque, NULL);
+    ret = vmstate_subsection_load(f, vmsd, opaque, errp);
      if (ret != 0) {
          qemu_file_set_error(f, ret);
          return ret;
      }
      if (vmsd->post_load) {
          ret = vmsd->post_load(opaque, version_id);
+        if (ret < 0) {
+            error_setg(errp, "VM Post load failed for: %s, version_id: %d,"
+                       "minimum_version: %d, ret: %d", vmsd->name,

This error message lacks a whitespace between "," and "minimum_version".

By the way, I prefer not to have line breaks in string literals to ease code search.

While QEMU's coding style guide says nothing about the length limit for a line with a string literal, scripts/checkpatch.pl make an exemption for such a line.

scripts/checkpatch.pl came from Linux, and Linux's coding style guide says:
> However, never break user-visible strings such as printk messages
> because that breaks the ability to grep for them.

https://www.kernel.org/doc/html/v6.15/process/coding-style.html#breaking-long-lines-and-strings

While we don't have to follow Linux's style, I think this particular statement makes sense for QEMU too.

+                       vmsd->version_id, vmsd->minimum_version_id, ret);
+        }
      }
      trace_vmstate_load_state_end(vmsd->name, "end", ret);
      return ret;
@@ -607,11 +618,11 @@ static int vmstate_subsection_load(QEMUFile *f, const 
VMStateDescription *vmsd,
          qemu_file_skip(f, len); /* idstr */
          version_id = qemu_get_be32(f);
- ret = vmstate_load_state(f, sub_vmsd, opaque, version_id);
+        ret = vmstate_load_state(f, sub_vmsd, opaque, version_id, errp);
          if (ret) {
              trace_vmstate_subsection_load_bad(vmsd->name, idstr, "(child)");
-            error_setg(errp, "Loading VM subsection '%s' in '%s' failed : %d",
-                       idstr, vmsd->name, ret);
+            error_prepend(errp, "Loading VM subsection '%s'"
+                          "in '%s' failed : %d ", idstr, vmsd->name, ret);
              return ret;
          }
      }
diff --git a/tests/unit/test-vmstate.c b/tests/unit/test-vmstate.c
index 
63f28f26f45691a70936d33e7341d16477a3471f..ca5e0ba1e3e5e2bb0a1ce39143a292f2c6f9420a
 100644
--- a/tests/unit/test-vmstate.c
+++ b/tests/unit/test-vmstate.c
@@ -114,7 +114,7 @@ static int load_vmstate_one(const VMStateDescription *desc, 
void *obj,
      qemu_fclose(f);
f = open_test_file(false);
-    ret = vmstate_load_state(f, desc, obj, version);
+    ret = vmstate_load_state(f, desc, obj, version, NULL);
      if (ret) {
          g_assert(qemu_file_get_error(f));
      } else{
@@ -365,7 +365,7 @@ static void test_load_v1(void)
QEMUFile *loading = open_test_file(false);
      TestStruct obj = { .b = 200, .e = 500, .f = 600 };
-    vmstate_load_state(loading, &vmstate_versioned, &obj, 1);
+    vmstate_load_state(loading, &vmstate_versioned, &obj, 1, NULL);
      g_assert(!qemu_file_get_error(loading));
      g_assert_cmpint(obj.a, ==, 10);
      g_assert_cmpint(obj.b, ==, 200);
@@ -391,7 +391,7 @@ static void test_load_v2(void)
QEMUFile *loading = open_test_file(false);
      TestStruct obj;
-    vmstate_load_state(loading, &vmstate_versioned, &obj, 2);
+    vmstate_load_state(loading, &vmstate_versioned, &obj, 2, NULL);
      g_assert_cmpint(obj.a, ==, 10);
      g_assert_cmpint(obj.b, ==, 20);
      g_assert_cmpint(obj.c, ==, 30);
@@ -480,7 +480,7 @@ static void test_load_noskip(void)
QEMUFile *loading = open_test_file(false);
      TestStruct obj = { .skip_c_e = false };
-    vmstate_load_state(loading, &vmstate_skipping, &obj, 2);
+    vmstate_load_state(loading, &vmstate_skipping, &obj, 2, NULL);
      g_assert(!qemu_file_get_error(loading));
      g_assert_cmpint(obj.a, ==, 10);
      g_assert_cmpint(obj.b, ==, 20);
@@ -504,7 +504,7 @@ static void test_load_skip(void)
QEMUFile *loading = open_test_file(false);
      TestStruct obj = { .skip_c_e = true, .c = 300, .e = 500 };
-    vmstate_load_state(loading, &vmstate_skipping, &obj, 2);
+    vmstate_load_state(loading, &vmstate_skipping, &obj, 2, NULL);
      g_assert(!qemu_file_get_error(loading));
      g_assert_cmpint(obj.a, ==, 10);
      g_assert_cmpint(obj.b, ==, 20);
@@ -773,7 +773,7 @@ static void test_load_q(void)
      TestQtailq tgt;
QTAILQ_INIT(&tgt.q);
-    vmstate_load_state(fload, &vmstate_q, &tgt, 1);
+    vmstate_load_state(fload, &vmstate_q, &tgt, 1, NULL);
      char eof = qemu_get_byte(fload);
      g_assert(!qemu_file_get_error(fload));
      g_assert_cmpint(tgt.i16, ==, obj_q.i16);
@@ -1127,7 +1127,7 @@ static void test_gtree_load_domain(void)
fload = open_test_file(false); - vmstate_load_state(fload, &vmstate_domain, dest_domain, 1);
+    vmstate_load_state(fload, &vmstate_domain, dest_domain, 1, NULL);
      eof = qemu_get_byte(fload);
      g_assert(!qemu_file_get_error(fload));
      g_assert_cmpint(orig_domain->id, ==, dest_domain->id);
@@ -1241,7 +1241,7 @@ static void test_gtree_load_iommu(void)
      qemu_fclose(fsave);
fload = open_test_file(false);
-    vmstate_load_state(fload, &vmstate_iommu, dest_iommu, 1);
+    vmstate_load_state(fload, &vmstate_iommu, dest_iommu, 1, NULL);
      eof = qemu_get_byte(fload);
      g_assert(!qemu_file_get_error(fload));
      g_assert_cmpint(orig_iommu->id, ==, dest_iommu->id);
@@ -1376,7 +1376,7 @@ static void test_load_qlist(void)
      qemu_fclose(fsave);
fload = open_test_file(false);
-    vmstate_load_state(fload, &vmstate_container, dest_container, 1);
+    vmstate_load_state(fload, &vmstate_container, dest_container, 1, NULL);
      eof = qemu_get_byte(fload);
      g_assert(!qemu_file_get_error(fload));
      g_assert_cmpint(eof, ==, QEMU_VM_EOF);
diff --git a/ui/vdagent.c b/ui/vdagent.c
index 
c0746fe5b168fdc7aeb4866de2ba0c3387566649..83457dee0767433ad0778b37b41b9c673a0e1860
 100644
--- a/ui/vdagent.c
+++ b/ui/vdagent.c
@@ -1008,7 +1008,7 @@ static int get_cbinfo(QEMUFile *f, void *pv, size_t size,
vdagent_clipboard_peer_register(vd); - ret = vmstate_load_state(f, &vmstate_cbinfo_array, &cbinfo, 0);
+    ret = vmstate_load_state(f, &vmstate_cbinfo_array, &cbinfo, 0, NULL);
      if (ret) {
          return ret;
      }



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