[PATCH v5 00/23] migration: propagate vTPM errors using Error objects

[PATCH v5 00/23] migration: propagate vTPM errors using Error objects

[Arun Menon]

Hello,

Currently, when a migration of a VM with an encrypted vTPM
fails on the destination host (e.g., due to a mismatch in secret values),
the error message displayed on the source host is generic and unhelpful.

For example, a typical error looks like this:
"operation failed: job 'migration out' failed: Sibling indicated error 1.
operation failed: job 'migration in' failed: load of migration failed:
Input/output error"

This message does not provide any specific indication of a vTPM failure.
Such generic errors are logged using error_report(), which prints to
the console/monitor but does not make the detailed error accessible via
the QMP query-migrate command.

This series addresses the issue, by ensuring that specific TPM error
messages are propagated via the QEMU Error object.
To make this possible,
- A set of functions in the call stack is changed
  to incorporate an Error object as an additional parameter.
- Also, the TPM backend makes use of a new hook called post_load_errp()
  that explicitly passes an Error object.

It is organized as follows,
 - Patches 1-21 focuses on pushing Error object into the functions
   that are important in the call stack where TPM errors are observed.
   We still need to make changes in rest of the functions in savevm.c
   such that they also incorporate the errp object for propagating errors.
 - Patch 22 introduces the new variants of the hooks in VMStateDescription
   structure. These hooks should be used in future implementations.
 - Patch 23 focuses on changing the TPM backend such that the errors are
   set in the Error object.

While this series focuses specifically on TPM error reporting during
live migration, it lays the groundwork for broader improvements.
A lot of methods in savevm.c that previously returned an integer now capture
errors in the Error object, enabling other modules to adopt the
post_load_errp hook in the future.

One such change previously attempted:
https://lists.gnu.org/archive/html/qemu-devel/2021-02/msg01727.html

Resolves: https://issues.redhat.com/browse/RHEL-82826

Signed-off-by: Arun Menon <armenon@redhat.com>
---
Changes in v5:
- Solve a bug that set errp even though it was not NULL, pointed out by Fabiano in v4.
- Link to v4: https://lore.kernel.org/qemu-devel/20250716-propagate_tpm_error-v4-0-7141902077c0@redhat.com

Changes in v4:
- Split the patches into smaller ones based on functions. Pass NULL in the
  caller until errp is made available. Every function that has an
  Error **errp object passed to it, ensures that it sets the errp object
  in case of failure.
- A few more functions within loadvm_process_command() now handle errors using
  the errp object. I've converted these for consistency, taking Daniel's
  patches (link above) as a reference.
- Along with the post_load_errp() hook, other duplicate hooks are also introduced.
  This will enable us to migrate to the newer versions eventually.
- Fix some semantic errors, like using error_propagate_prepend() in places where
  we need to preserve existing behaviour of accumulating the error in local_err
  and then propagating it to errp. This can be refactored in a later commit.
- Add more information in commit messages explaining the changes.
- Link to v3: https://lore.kernel.org/qemu-devel/20250702-propagate_tpm_error-v3-0-986d94540528@redhat.com

Changes in v3:
- Split the 2nd patch into 2. Introducing post_load_with_error() hook
  has been separated from using it in the backends TPM module. This is
  so that it can be acknowledged.
- Link to v2: https://lore.kernel.org/qemu-devel/20250627-propagate_tpm_error-v2-0-85990c89da29@redhat.com

Changes in v2:
- Combine the first two changes into one, focusing on passing the
  Error object (errp) consistently through functions involved in
  loading the VM's state. Other functions are not yet changed.
- As suggested in the review comment, add null checks for errp
  before adding error messages, preventing crashes.
  We also now correctly set errors when post-copy migration fails.
- In process_incoming_migration_co(), switch to error_prepend
  instead of error_setg. This means we now null-check local_err in
  the "fail" section before using it, preventing dereferencing issues.
- Link to v1: https://lore.kernel.org/qemu-devel/20250624-propagate_tpm_error-v1-0-2171487a593d@redhat.com

---
Arun Menon (23):
      migration: push Error **errp into vmstate_subsection_load()
      migration: push Error **errp into vmstate_load_state()
      migration: push Error **errp into qemu_loadvm_state_header()
      migration: push Error **errp into vmstate_load()
      migration: push Error **errp into qemu_loadvm_section_start_full()
      migration: push Error **errp into qemu_loadvm_section_part_end()
      migration: push Error **errp into loadvm_process_command()
      migration: push Error **errp into loadvm_handle_cmd_packaged()
      migration: push Error **errp into ram_postcopy_incoming_init()
      migration: push Error **errp into loadvm_postcopy_handle_advise()
      migration: push Error **errp into loadvm_postcopy_handle_listen()
      migration: push Error **errp into loadvm_postcopy_handle_run()
      migration: push Error **errp into loadvm_postcopy_ram_handle_discard()
      migration: make loadvm_postcopy_handle_resume() void
      migration: push Error **errp into loadvm_handle_recv_bitmap()
      migration: push Error **errp into loadvm_process_enable_colo()
      migration: push Error **errp into loadvm_postcopy_handle_switchover_start()
      migration: push Error **errp into qemu_loadvm_state_main()
      migration: push Error **errp into qemu_loadvm_state()
      migration: push Error **errp into qemu_load_device_state()
      migration: Capture error in postcopy_ram_listen_thread()
      migration: Add error-parameterized function variants in VMSD struct
      backends/tpm: Propagate vTPM error on migration failure

 backends/tpm/tpm_emulator.c |  39 +++---
 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/colo.h    |   2 +-
 include/migration/vmstate.h |  13 +-
 migration/colo.c            |  10 +-
 migration/cpr.c             |   4 +-
 migration/migration.c       |  19 +--
 migration/postcopy-ram.c    |   9 +-
 migration/postcopy-ram.h    |   2 +-
 migration/ram.c             |  14 +--
 migration/ram.h             |   4 +-
 migration/savevm.c          | 293 +++++++++++++++++++++++++-------------------
 migration/savevm.h          |   7 +-
 migration/vmstate-types.c   |  10 +-
 migration/vmstate.c         |  83 +++++++++----
 tests/unit/test-vmstate.c   |  18 +--
 ui/vdagent.c                |   2 +-
 24 files changed, 321 insertions(+), 226 deletions(-)
---
base-commit: f96b157ebb93f94cd56ebbc99bc20982b8fd86ef
change-id: 20250624-propagate_tpm_error-bf4ae6c23d30

Best regards,
-- 
Arun Menon <armenon@redhat.com>

[PATCH v5 01/23] migration: push Error **errp into vmstate_subsection_load()

[Arun Menon]

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_subsection_load() must report an error
in errp, in case of failure.

Signed-off-by: Arun Menon <armenon@redhat.com>
---
 migration/vmstate.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/migration/vmstate.c b/migration/vmstate.c
index 5feaa3244d259874f03048326b2497e7db32e47c..526668a020562f303d2ddf030b1c8466659b67be 100644
--- a/migration/vmstate.c
+++ b/migration/vmstate.c
@@ -25,7 +25,7 @@ static int vmstate_subsection_save(QEMUFile *f, const VMStateDescription *vmsd,
                                    void *opaque, JSONWriter *vmdesc,
                                    Error **errp);
 static int vmstate_subsection_load(QEMUFile *f, const VMStateDescription *vmsd,
-                                   void *opaque);
+                                   void *opaque, Error **errp);
 
 /* Whether this field should exist for either save or load the VM? */
 static bool
@@ -225,7 +225,7 @@ int vmstate_load_state(QEMUFile *f, const VMStateDescription *vmsd,
         field++;
     }
     assert(field->flags == VMS_END);
-    ret = vmstate_subsection_load(f, vmsd, opaque);
+    ret = vmstate_subsection_load(f, vmsd, opaque, NULL);
     if (ret != 0) {
         qemu_file_set_error(f, ret);
         return ret;
@@ -566,7 +566,7 @@ vmstate_get_subsection(const VMStateDescription * const *sub,
 }
 
 static int vmstate_subsection_load(QEMUFile *f, const VMStateDescription *vmsd,
-                                   void *opaque)
+                                   void *opaque, Error **errp)
 {
     trace_vmstate_subsection_load(vmsd->name);
 
@@ -598,6 +598,7 @@ static int vmstate_subsection_load(QEMUFile *f, const VMStateDescription *vmsd,
         sub_vmsd = vmstate_get_subsection(vmsd->subsections, idstr);
         if (sub_vmsd == NULL) {
             trace_vmstate_subsection_load_bad(vmsd->name, idstr, "(lookup)");
+            error_setg(errp, "VM subsection does not exist");
             return -ENOENT;
         }
         qemu_file_skip(f, 1); /* subsection */
@@ -608,6 +609,7 @@ static int vmstate_subsection_load(QEMUFile *f, const VMStateDescription *vmsd,
         ret = vmstate_load_state(f, sub_vmsd, opaque, version_id);
         if (ret) {
             trace_vmstate_subsection_load_bad(vmsd->name, idstr, "(child)");
+            error_setg(errp, "Loading VM subsection failed : %d", ret);
             return ret;
         }
     }

-- 
2.50.0

[PATCH v5 02/23] migration: push Error **errp into vmstate_load_state()

[Arun Menon]

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 <armenon@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         | 43 +++++++++++++++++++++++++++----------------
 tests/unit/test-vmstate.c   | 18 +++++++++---------
 ui/vdagent.c                |  2 +-
 15 files changed, 58 insertions(+), 45 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 526668a020562f303d2ddf030b1c8466659b67be..078a00003023cc248fb16f05017d4c4251fd86df 100644
--- a/migration/vmstate.c
+++ b/migration/vmstate.c
@@ -132,29 +132,30 @@ 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 : %d", ret);
             return ret;
         }
     }
@@ -192,10 +193,12 @@ 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 +214,35 @@ 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);
+                    if (errp != NULL) {
+                        error_prepend(errp, "Failed to load %s:%s ", vmsd->name,
+                                      field->name);
+                    } else {
+                        error_setg(errp, "Failed to load %s:%s", vmsd->name,
+                                   field->name);
+                    }
                     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",
+                       vmsd->name, field->name);
             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 : %d", ret);
+        }
     }
     trace_vmstate_load_state_end(vmsd->name, "end", ret);
     return ret;
@@ -606,10 +617,10 @@ 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 failed : %d", ret);
+            error_prepend(errp, "Loading VM subsection failed : %d ", 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;
     }

-- 
2.50.0

[PATCH v5 03/23] migration: push Error **errp into qemu_loadvm_state_header()

[Arun Menon]

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 qemu_loadvm_state_header() must report an error
in errp, in case of failure.

Signed-off-by: Arun Menon <armenon@redhat.com>
---
 migration/savevm.c | 25 ++++++++++++++++---------
 1 file changed, 16 insertions(+), 9 deletions(-)

diff --git a/migration/savevm.c b/migration/savevm.c
index ab947620f724874f325fb9fb59bef50b7c16fb51..3ccbc724eb808db09b77088a858ecc7f06b21155 100644
--- a/migration/savevm.c
+++ b/migration/savevm.c
@@ -2814,35 +2814,42 @@ qemu_loadvm_section_part_end(QEMUFile *f, uint8_t type)
     return 0;
 }
 
-static int qemu_loadvm_state_header(QEMUFile *f)
+static int qemu_loadvm_state_header(QEMUFile *f, Error **errp)
 {
     unsigned int v;
     int ret;
 
     v = qemu_get_be32(f);
     if (v != QEMU_VM_FILE_MAGIC) {
-        error_report("Not a migration stream");
+        error_setg(errp, "Not a migration stream, "
+                   "magic: %x != %x", v, QEMU_VM_FILE_MAGIC);
         return -EINVAL;
     }
 
     v = qemu_get_be32(f);
     if (v == QEMU_VM_FILE_VERSION_COMPAT) {
-        error_report("SaveVM v2 format is obsolete and don't work anymore");
+        error_setg(errp, "SaveVM v2 format is obsolete and don't "
+                   "work anymore, file version %x != %x",
+                   v, QEMU_VM_FILE_VERSION_COMPAT);
+
         return -ENOTSUP;
     }
     if (v != QEMU_VM_FILE_VERSION) {
-        error_report("Unsupported migration stream version");
+        error_setg(errp, "Unsupported migration stream "
+                   "version, file version %x != %x", v, QEMU_VM_FILE_VERSION);
         return -ENOTSUP;
     }
 
     if (migrate_get_current()->send_configuration) {
-        if (qemu_get_byte(f) != QEMU_VM_CONFIGURATION) {
-            error_report("Configuration section missing");
+        v = qemu_get_byte(f);
+        if (v != QEMU_VM_CONFIGURATION) {
+            error_setg(errp, "Configuration section missing,"
+                       "%x != %x", v, QEMU_VM_CONFIGURATION);
             return -EINVAL;
         }
-        ret = vmstate_load_state(f, &vmstate_configuration, &savevm_state, 0,
-                                 NULL);
 
+        ret = vmstate_load_state(f, &vmstate_configuration, &savevm_state, 0,
+                                 errp);
         if (ret) {
             return ret;
         }
@@ -3119,7 +3126,7 @@ int qemu_loadvm_state(QEMUFile *f)
 
     qemu_loadvm_thread_pool_create(mis);
 
-    ret = qemu_loadvm_state_header(f);
+    ret = qemu_loadvm_state_header(f, NULL);
     if (ret) {
         return ret;
     }

-- 
2.50.0

[PATCH v5 04/23] migration: push Error **errp into vmstate_load()

[Arun Menon]

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() must report an error
in errp, in case of failure.

Signed-off-by: Arun Menon <armenon@redhat.com>
---
 migration/savevm.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/migration/savevm.c b/migration/savevm.c
index 3ccbc724eb808db09b77088a858ecc7f06b21155..1c1a46e4a01f812b559c451d278916426aa1cf40 100644
--- a/migration/savevm.c
+++ b/migration/savevm.c
@@ -963,14 +963,14 @@ void vmstate_unregister(VMStateIf *obj, const VMStateDescription *vmsd,
     }
 }
 
-static int vmstate_load(QEMUFile *f, SaveStateEntry *se)
+static int vmstate_load(QEMUFile *f, SaveStateEntry *se, Error **errp)
 {
     trace_vmstate_load(se->idstr, se->vmsd ? se->vmsd->name : "(old)");
     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,
-                              NULL);
+                              errp);
 }
 
 static void vmstate_save_old_style(QEMUFile *f, SaveStateEntry *se,
@@ -2741,7 +2741,7 @@ qemu_loadvm_section_start_full(QEMUFile *f, uint8_t type)
         start_ts = qemu_clock_get_us(QEMU_CLOCK_REALTIME);
     }
 
-    ret = vmstate_load(f, se);
+    ret = vmstate_load(f, se, NULL);
     if (ret < 0) {
         error_report("error while loading state for instance 0x%"PRIx32" of"
                      " device '%s'", instance_id, idstr);
@@ -2794,7 +2794,7 @@ qemu_loadvm_section_part_end(QEMUFile *f, uint8_t type)
         start_ts = qemu_clock_get_us(QEMU_CLOCK_REALTIME);
     }
 
-    ret = vmstate_load(f, se);
+    ret = vmstate_load(f, se, NULL);
     if (ret < 0) {
         error_report("error while loading state section id %d(%s)",
                      section_id, se->idstr);

-- 
2.50.0

[PATCH v5 05/23] migration: push Error **errp into qemu_loadvm_section_start_full()

[Arun Menon]

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 qemu_loadvm_section_start_full() must report an error
in errp, in case of failure.

Signed-off-by: Arun Menon <armenon@redhat.com>
---
 migration/savevm.c | 34 ++++++++++++++++++----------------
 1 file changed, 18 insertions(+), 16 deletions(-)

diff --git a/migration/savevm.c b/migration/savevm.c
index 1c1a46e4a01f812b559c451d278916426aa1cf40..63125971751394b72efc9bcaf7c4364715eef07f 100644
--- a/migration/savevm.c
+++ b/migration/savevm.c
@@ -2684,7 +2684,7 @@ static bool check_section_footer(QEMUFile *f, SaveStateEntry *se)
 }
 
 static int
-qemu_loadvm_section_start_full(QEMUFile *f, uint8_t type)
+qemu_loadvm_section_start_full(QEMUFile *f, uint8_t type, Error **errp)
 {
     bool trace_downtime = (type == QEMU_VM_SECTION_FULL);
     uint32_t instance_id, version_id, section_id;
@@ -2696,8 +2696,8 @@ qemu_loadvm_section_start_full(QEMUFile *f, uint8_t type)
     /* Read section start */
     section_id = qemu_get_be32(f);
     if (!qemu_get_counted_string(f, idstr)) {
-        error_report("Unable to read ID string for section %u",
-                     section_id);
+        error_setg(errp, "Unable to read ID string for section %u",
+                   section_id);
         return -EINVAL;
     }
     instance_id = qemu_get_be32(f);
@@ -2705,8 +2705,8 @@ qemu_loadvm_section_start_full(QEMUFile *f, uint8_t type)
 
     ret = qemu_file_get_error(f);
     if (ret) {
-        error_report("%s: Failed to read instance/version ID: %d",
-                     __func__, ret);
+        error_setg(errp, "%s: Failed to read instance/version ID: %d",
+                   __func__, ret);
         return ret;
     }
 
@@ -2715,17 +2715,17 @@ qemu_loadvm_section_start_full(QEMUFile *f, uint8_t type)
     /* Find savevm section */
     se = find_se(idstr, instance_id);
     if (se == NULL) {
-        error_report("Unknown savevm section or instance '%s' %"PRIu32". "
-                     "Make sure that your current VM setup matches your "
-                     "saved VM setup, including any hotplugged devices",
-                     idstr, instance_id);
+        error_setg(errp, "Unknown savevm section or instance '%s' %"PRIu32". "
+                   "Make sure that your current VM setup matches your "
+                   "saved VM setup, including any hotplugged devices",
+                   idstr, instance_id);
         return -EINVAL;
     }
 
     /* Validate version */
     if (version_id > se->version_id) {
-        error_report("savevm: unsupported version %d for '%s' v%d",
-                     version_id, idstr, se->version_id);
+        error_setg(errp, "savevm: unsupported version %d for '%s' v%d",
+                   version_id, idstr, se->version_id);
         return -EINVAL;
     }
     se->load_version_id = version_id;
@@ -2733,7 +2733,7 @@ qemu_loadvm_section_start_full(QEMUFile *f, uint8_t type)
 
     /* Validate if it is a device's state */
     if (xen_enabled() && se->is_ram) {
-        error_report("loadvm: %s RAM loading not allowed on Xen", idstr);
+        error_setg(errp, "loadvm: %s RAM loading not allowed on Xen", idstr);
         return -EINVAL;
     }
 
@@ -2741,10 +2741,11 @@ qemu_loadvm_section_start_full(QEMUFile *f, uint8_t type)
         start_ts = qemu_clock_get_us(QEMU_CLOCK_REALTIME);
     }
 
-    ret = vmstate_load(f, se, NULL);
+    ret = vmstate_load(f, se, errp);
     if (ret < 0) {
-        error_report("error while loading state for instance 0x%"PRIx32" of"
-                     " device '%s'", instance_id, idstr);
+        error_prepend(errp, "error while loading state for"
+                      " instance 0x%"PRIx32" of"
+                      " device '%s' ", instance_id, idstr);
         return ret;
     }
 
@@ -2755,6 +2756,7 @@ qemu_loadvm_section_start_full(QEMUFile *f, uint8_t type)
     }
 
     if (!check_section_footer(f, se)) {
+        error_setg(errp, "Reading footer section failed");
         return -EINVAL;
     }
 
@@ -3055,7 +3057,7 @@ retry:
         switch (section_type) {
         case QEMU_VM_SECTION_START:
         case QEMU_VM_SECTION_FULL:
-            ret = qemu_loadvm_section_start_full(f, section_type);
+            ret = qemu_loadvm_section_start_full(f, section_type, NULL);
             if (ret < 0) {
                 goto out;
             }

-- 
2.50.0

[PATCH v5 06/23] migration: push Error **errp into qemu_loadvm_section_part_end()

[Arun Menon]

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 qemu_loadvm_section_part_end() must report an error
in errp, in case of failure.

Signed-off-by: Arun Menon <armenon@redhat.com>
---
 migration/savevm.c | 17 +++++++++--------
 1 file changed, 9 insertions(+), 8 deletions(-)

diff --git a/migration/savevm.c b/migration/savevm.c
index 63125971751394b72efc9bcaf7c4364715eef07f..22d73999595384519c755c9416b74ba1263a8bb9 100644
--- a/migration/savevm.c
+++ b/migration/savevm.c
@@ -2764,7 +2764,7 @@ qemu_loadvm_section_start_full(QEMUFile *f, uint8_t type, Error **errp)
 }
 
 static int
-qemu_loadvm_section_part_end(QEMUFile *f, uint8_t type)
+qemu_loadvm_section_part_end(QEMUFile *f, uint8_t type, Error **errp)
 {
     bool trace_downtime = (type == QEMU_VM_SECTION_END);
     int64_t start_ts, end_ts;
@@ -2776,8 +2776,8 @@ qemu_loadvm_section_part_end(QEMUFile *f, uint8_t type)
 
     ret = qemu_file_get_error(f);
     if (ret) {
-        error_report("%s: Failed to read section ID: %d",
-                     __func__, ret);
+        error_setg(errp, "%s: Failed to read section ID: %d",
+                   __func__, ret);
         return ret;
     }
 
@@ -2788,7 +2788,7 @@ qemu_loadvm_section_part_end(QEMUFile *f, uint8_t type)
         }
     }
     if (se == NULL) {
-        error_report("Unknown savevm section %d", section_id);
+        error_setg(errp, "Unknown savevm section %d", section_id);
         return -EINVAL;
     }
 
@@ -2796,10 +2796,10 @@ qemu_loadvm_section_part_end(QEMUFile *f, uint8_t type)
         start_ts = qemu_clock_get_us(QEMU_CLOCK_REALTIME);
     }
 
-    ret = vmstate_load(f, se, NULL);
+    ret = vmstate_load(f, se, errp);
     if (ret < 0) {
-        error_report("error while loading state section id %d(%s)",
-                     section_id, se->idstr);
+        error_prepend(errp, "error while loading state section id %d(%s) ",
+                      section_id, se->idstr);
         return ret;
     }
 
@@ -2810,6 +2810,7 @@ qemu_loadvm_section_part_end(QEMUFile *f, uint8_t type)
     }
 
     if (!check_section_footer(f, se)) {
+        error_setg(errp, "Check section footer error");
         return -EINVAL;
     }
 
@@ -3064,7 +3065,7 @@ retry:
             break;
         case QEMU_VM_SECTION_PART:
         case QEMU_VM_SECTION_END:
-            ret = qemu_loadvm_section_part_end(f, section_type);
+            ret = qemu_loadvm_section_part_end(f, section_type, NULL);
             if (ret < 0) {
                 goto out;
             }

-- 
2.50.0

[PATCH v5 07/23] migration: push Error **errp into loadvm_process_command()

[Arun Menon]

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 loadvm_process_command() must report an error
in errp, in case of failure.

Signed-off-by: Arun Menon <armenon@redhat.com>
---
 migration/savevm.c | 89 ++++++++++++++++++++++++++++++++++++++++--------------
 1 file changed, 67 insertions(+), 22 deletions(-)

diff --git a/migration/savevm.c b/migration/savevm.c
index 22d73999595384519c755c9416b74ba1263a8bb9..98711bb38a4548d4f168459f729f604a78716c25 100644
--- a/migration/savevm.c
+++ b/migration/savevm.c
@@ -2540,12 +2540,13 @@ static int loadvm_postcopy_handle_switchover_start(void)
  * LOADVM_QUIT All good, but exit the loop
  * <0          Error
  */
-static int loadvm_process_command(QEMUFile *f)
+static int loadvm_process_command(QEMUFile *f, Error **errp)
 {
     MigrationIncomingState *mis = migration_incoming_get_current();
     uint16_t cmd;
     uint16_t len;
     uint32_t tmp32;
+    int ret;
 
     cmd = qemu_get_be16(f);
     len = qemu_get_be16(f);
@@ -2556,16 +2557,16 @@ static int loadvm_process_command(QEMUFile *f)
     }
 
     if (cmd >= MIG_CMD_MAX || cmd == MIG_CMD_INVALID) {
-        error_report("MIG_CMD 0x%x unknown (len 0x%x)", cmd, len);
+        error_setg(errp, "MIG_CMD 0x%x unknown (len 0x%x)", cmd, len);
         return -EINVAL;
     }
 
     trace_loadvm_process_command(mig_cmd_args[cmd].name, len);
 
     if (mig_cmd_args[cmd].len != -1 && mig_cmd_args[cmd].len != len) {
-        error_report("%s received with bad length - expecting %zu, got %d",
-                     mig_cmd_args[cmd].name,
-                     (size_t)mig_cmd_args[cmd].len, len);
+        error_setg(errp, "%s received with bad length - expecting %zu, got %d",
+                   mig_cmd_args[cmd].name,
+                   (size_t)mig_cmd_args[cmd].len, len);
         return -ERANGE;
     }
 
@@ -2578,7 +2579,7 @@ static int loadvm_process_command(QEMUFile *f)
         }
         mis->to_src_file = qemu_file_get_return_path(f);
         if (!mis->to_src_file) {
-            error_report("CMD_OPEN_RETURN_PATH failed");
+            error_setg(errp, "CMD_OPEN_RETURN_PATH failed");
             return -1;
         }
 
@@ -2588,11 +2589,10 @@ static int loadvm_process_command(QEMUFile *f)
          * been created.
          */
         if (migrate_switchover_ack() && !mis->switchover_ack_pending_num) {
-            int ret = migrate_send_rp_switchover_ack(mis);
+            ret = migrate_send_rp_switchover_ack(mis);
             if (ret) {
-                error_report(
-                    "Could not send switchover ack RP MSG, err %d (%s)", ret,
-                    strerror(-ret));
+                error_setg(errp, "Could not send switchover ack "
+                           "RP MSG, err %d (%s)", ret, strerror(-ret));
                 return ret;
             }
         }
@@ -2602,39 +2602,84 @@ static int loadvm_process_command(QEMUFile *f)
         tmp32 = qemu_get_be32(f);
         trace_loadvm_process_command_ping(tmp32);
         if (!mis->to_src_file) {
-            error_report("CMD_PING (0x%x) received with no return path",
-                         tmp32);
+            error_setg(errp, "CMD_PING (0x%x) received with no return path",
+                       tmp32);
             return -1;
         }
         migrate_send_rp_pong(mis, tmp32);
         break;
 
     case MIG_CMD_PACKAGED:
-        return loadvm_handle_cmd_packaged(mis);
+        ret = loadvm_handle_cmd_packaged(mis);
+        if (ret < 0) {
+            error_setg(errp, "Failed to load device state command: %d", ret);
+            return -1;
+        }
+        return ret;
 
     case MIG_CMD_POSTCOPY_ADVISE:
-        return loadvm_postcopy_handle_advise(mis, len);
+        ret = loadvm_postcopy_handle_advise(mis, len);
+        if (ret < 0) {
+            error_setg(errp, "Failed to load device state command: %d", ret);
+            return -1;
+        }
+        return ret;
 
     case MIG_CMD_POSTCOPY_LISTEN:
-        return loadvm_postcopy_handle_listen(mis);
+        ret = loadvm_postcopy_handle_listen(mis);
+        if (ret < 0) {
+            error_setg(errp, "Failed to load device state command: %d", ret);
+            return -1;
+        }
+        return ret;
 
     case MIG_CMD_POSTCOPY_RUN:
-        return loadvm_postcopy_handle_run(mis);
+        ret = loadvm_postcopy_handle_run(mis);
+        if (ret < 0) {
+            error_setg(errp, "Failed to load device state command: %d", ret);
+            return -1;
+        }
+        return ret;
 
     case MIG_CMD_POSTCOPY_RAM_DISCARD:
-        return loadvm_postcopy_ram_handle_discard(mis, len);
+        ret = loadvm_postcopy_ram_handle_discard(mis, len);
+        if (ret < 0) {
+            error_setg(errp, "Failed to load device state command: %d", ret);
+            return -1;
+        }
+        return ret;
 
     case MIG_CMD_POSTCOPY_RESUME:
-        return loadvm_postcopy_handle_resume(mis);
+        ret = loadvm_postcopy_handle_resume(mis);
+        if (ret < 0) {
+            error_setg(errp, "Failed to load device state command: %d", ret);
+            return -1;
+        }
+        return ret;
 
     case MIG_CMD_RECV_BITMAP:
-        return loadvm_handle_recv_bitmap(mis, len);
+        ret = loadvm_handle_recv_bitmap(mis, len);
+        if (ret < 0) {
+            error_setg(errp, "Failed to load device state command: %d", ret);
+            return -1;
+        }
+        return ret;
 
     case MIG_CMD_ENABLE_COLO:
-        return loadvm_process_enable_colo(mis);
+        ret = loadvm_process_enable_colo(mis);
+        if (ret < 0) {
+            error_setg(errp, "Failed to load device state command: %d", ret);
+            return -1;
+        }
+        return ret;
 
     case MIG_CMD_SWITCHOVER_START:
-        return loadvm_postcopy_handle_switchover_start();
+        ret = loadvm_postcopy_handle_switchover_start();
+        if (ret < 0) {
+            error_setg(errp, "Failed to load device state command: %d", ret);
+            return -1;
+        }
+        return ret;
     }
 
     return 0;
@@ -3071,7 +3116,7 @@ retry:
             }
             break;
         case QEMU_VM_COMMAND:
-            ret = loadvm_process_command(f);
+            ret = loadvm_process_command(f, NULL);
             trace_qemu_loadvm_state_section_command(ret);
             if ((ret < 0) || (ret == LOADVM_QUIT)) {
                 goto out;

-- 
2.50.0

[PATCH v5 08/23] migration: push Error **errp into loadvm_handle_cmd_packaged()

[Arun Menon]

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 loadvm_handle_cmd_packaged() must report an error
in errp, in case of failure.

Signed-off-by: Arun Menon <armenon@redhat.com>
---
 migration/savevm.c | 18 ++++++++----------
 1 file changed, 8 insertions(+), 10 deletions(-)

diff --git a/migration/savevm.c b/migration/savevm.c
index 98711bb38a4548d4f168459f729f604a78716c25..d1edeaac5f2a5df2f6d94357388be807a938b2ef 100644
--- a/migration/savevm.c
+++ b/migration/savevm.c
@@ -2399,7 +2399,7 @@ static int loadvm_postcopy_handle_resume(MigrationIncomingState *mis)
  * Returns: Negative values on error
  *
  */
-static int loadvm_handle_cmd_packaged(MigrationIncomingState *mis)
+static int loadvm_handle_cmd_packaged(MigrationIncomingState *mis, Error **errp)
 {
     int ret;
     size_t length;
@@ -2409,7 +2409,7 @@ static int loadvm_handle_cmd_packaged(MigrationIncomingState *mis)
     trace_loadvm_handle_cmd_packaged(length);
 
     if (length > MAX_VM_CMD_PACKAGED_SIZE) {
-        error_report("Unreasonably large packaged state: %zu", length);
+        error_setg(errp, "Unreasonably large packaged state: %zu", length);
         return -1;
     }
 
@@ -2420,8 +2420,8 @@ static int loadvm_handle_cmd_packaged(MigrationIncomingState *mis)
                           length);
     if (ret != length) {
         object_unref(OBJECT(bioc));
-        error_report("CMD_PACKAGED: Buffer receive fail ret=%d length=%zu",
-                     ret, length);
+        error_setg(errp, "CMD_PACKAGED: Buffer receive fail ret=%d length=%zu",
+                   ret, length);
         return (ret < 0) ? ret : -EAGAIN;
     }
     bioc->usage += length;
@@ -2451,6 +2451,9 @@ static int loadvm_handle_cmd_packaged(MigrationIncomingState *mis)
     } while (1);
 
     ret = qemu_loadvm_state_main(packf, mis);
+    if (ret < 0) {
+        error_setg(errp, "VM state load failed: %d", ret);
+    }
     trace_loadvm_handle_cmd_packaged_main(ret);
     qemu_fclose(packf);
     object_unref(OBJECT(bioc));
@@ -2610,12 +2613,7 @@ static int loadvm_process_command(QEMUFile *f, Error **errp)
         break;
 
     case MIG_CMD_PACKAGED:
-        ret = loadvm_handle_cmd_packaged(mis);
-        if (ret < 0) {
-            error_setg(errp, "Failed to load device state command: %d", ret);
-            return -1;
-        }
-        return ret;
+        return loadvm_handle_cmd_packaged(mis, errp);
 
     case MIG_CMD_POSTCOPY_ADVISE:
         ret = loadvm_postcopy_handle_advise(mis, len);

-- 
2.50.0

[PATCH v5 09/23] migration: push Error **errp into ram_postcopy_incoming_init()

[Arun Menon]

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 ram_postcopy_incoming_init() must report an error
in errp, in case of failure.

Signed-off-by: Arun Menon <armenon@redhat.com>
---
 migration/postcopy-ram.c | 9 ++++++---
 migration/postcopy-ram.h | 2 +-
 migration/ram.c          | 6 +++---
 migration/ram.h          | 2 +-
 migration/savevm.c       | 2 +-
 5 files changed, 12 insertions(+), 9 deletions(-)

diff --git a/migration/postcopy-ram.c b/migration/postcopy-ram.c
index 45af9a361e8eacaad0fb217a5da2c5004416c1da..05617e5fbcad62226a54fe17d9f7d9a316baf1e4 100644
--- a/migration/postcopy-ram.c
+++ b/migration/postcopy-ram.c
@@ -681,6 +681,7 @@ out:
  */
 static int init_range(RAMBlock *rb, void *opaque)
 {
+    Error **errp = opaque;
     const char *block_name = qemu_ram_get_idstr(rb);
     void *host_addr = qemu_ram_get_host_addr(rb);
     ram_addr_t offset = qemu_ram_get_offset(rb);
@@ -701,6 +702,8 @@ static int init_range(RAMBlock *rb, void *opaque)
      * (Precopy will just overwrite this data, so doesn't need the discard)
      */
     if (ram_discard_range(block_name, 0, length)) {
+        error_setg(errp, "failed to discard RAM block %s len=%zu",
+                   block_name, length);
         return -1;
     }
 
@@ -749,9 +752,9 @@ static int cleanup_range(RAMBlock *rb, void *opaque)
  * postcopy later; must be called prior to any precopy.
  * called from arch_init's similarly named ram_postcopy_incoming_init
  */
-int postcopy_ram_incoming_init(MigrationIncomingState *mis)
+int postcopy_ram_incoming_init(MigrationIncomingState *mis, Error **errp)
 {
-    if (foreach_not_ignored_block(init_range, NULL)) {
+    if (foreach_not_ignored_block(init_range, errp)) {
         return -1;
     }
 
@@ -1703,7 +1706,7 @@ bool postcopy_ram_supported_by_host(MigrationIncomingState *mis, Error **errp)
     return false;
 }
 
-int postcopy_ram_incoming_init(MigrationIncomingState *mis)
+int postcopy_ram_incoming_init(MigrationIncomingState *mis, Error **errp)
 {
     error_report("postcopy_ram_incoming_init: No OS support");
     return -1;
diff --git a/migration/postcopy-ram.h b/migration/postcopy-ram.h
index 3852141d7e37ab18bada4b46c137fef0969d0070..ca19433b246893fa5105bcebffb442c58a9a4f48 100644
--- a/migration/postcopy-ram.h
+++ b/migration/postcopy-ram.h
@@ -30,7 +30,7 @@ int postcopy_ram_incoming_setup(MigrationIncomingState *mis);
  * postcopy later; must be called prior to any precopy.
  * called from ram.c's similarly named ram_postcopy_incoming_init
  */
-int postcopy_ram_incoming_init(MigrationIncomingState *mis);
+int postcopy_ram_incoming_init(MigrationIncomingState *mis, Error **errp);
 
 /*
  * At the end of a migration where postcopy_ram_incoming_init was called.
diff --git a/migration/ram.c b/migration/ram.c
index 7208bc114fb5c366740db380ee6956a91b3871a0..8223183132dc0f558f45fbae3f4f832845730bd3 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -3708,7 +3708,7 @@ static int ram_load_cleanup(void *opaque)
 /**
  * ram_postcopy_incoming_init: allocate postcopy data structures
  *
- * Returns 0 for success and negative if there was one error
+ * Returns 0 for success and -1 if there was one error
  *
  * @mis: current migration incoming state
  *
@@ -3716,9 +3716,9 @@ static int ram_load_cleanup(void *opaque)
  * postcopy-ram. postcopy-ram's similarly names
  * postcopy_ram_incoming_init does the work.
  */
-int ram_postcopy_incoming_init(MigrationIncomingState *mis)
+int ram_postcopy_incoming_init(MigrationIncomingState *mis, Error **errp)
 {
-    return postcopy_ram_incoming_init(mis);
+    return postcopy_ram_incoming_init(mis, errp);
 }
 
 /**
diff --git a/migration/ram.h b/migration/ram.h
index 921c39a2c5c45bc2344be80854c46e4c10c09aeb..275709a99187f9429ccb4111e05281ec268ba0db 100644
--- a/migration/ram.h
+++ b/migration/ram.h
@@ -86,7 +86,7 @@ void ram_postcopy_migrated_memory_release(MigrationState *ms);
 void ram_postcopy_send_discard_bitmap(MigrationState *ms);
 /* For incoming postcopy discard */
 int ram_discard_range(const char *block_name, uint64_t start, size_t length);
-int ram_postcopy_incoming_init(MigrationIncomingState *mis);
+int ram_postcopy_incoming_init(MigrationIncomingState *mis, Error **errp);
 int ram_load_postcopy(QEMUFile *f, int channel);
 
 void ram_handle_zero(void *host, uint64_t size);
diff --git a/migration/savevm.c b/migration/savevm.c
index d1edeaac5f2a5df2f6d94357388be807a938b2ef..8eba151a693b7f2dc58853292c92024288eae81e 100644
--- a/migration/savevm.c
+++ b/migration/savevm.c
@@ -1983,7 +1983,7 @@ static int loadvm_postcopy_handle_advise(MigrationIncomingState *mis,
         return -1;
     }
 
-    if (ram_postcopy_incoming_init(mis)) {
+    if (ram_postcopy_incoming_init(mis, NULL)) {
         return -1;
     }
 

-- 
2.50.0

[PATCH v5 10/23] migration: push Error **errp into loadvm_postcopy_handle_advise()

[Arun Menon]

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 loadvm_postcopy_handle_advise() must report an error
in errp, in case of failure.

Signed-off-by: Arun Menon <armenon@redhat.com>
---
 migration/savevm.c | 39 +++++++++++++++++----------------------
 1 file changed, 17 insertions(+), 22 deletions(-)

diff --git a/migration/savevm.c b/migration/savevm.c
index 8eba151a693b7f2dc58853292c92024288eae81e..608560af35dc76813bf6e9b571df3bd343f0eeab 100644
--- a/migration/savevm.c
+++ b/migration/savevm.c
@@ -1906,39 +1906,39 @@ enum LoadVMExitCodes {
  * quickly.
  */
 static int loadvm_postcopy_handle_advise(MigrationIncomingState *mis,
-                                         uint16_t len)
+                                         uint16_t len, Error **errp)
 {
     PostcopyState ps = postcopy_state_set(POSTCOPY_INCOMING_ADVISE);
     uint64_t remote_pagesize_summary, local_pagesize_summary, remote_tps;
     size_t page_size = qemu_target_page_size();
-    Error *local_err = NULL;
 
     trace_loadvm_postcopy_handle_advise();
     if (ps != POSTCOPY_INCOMING_NONE) {
-        error_report("CMD_POSTCOPY_ADVISE in wrong postcopy state (%d)", ps);
+        error_setg(errp, "CMD_POSTCOPY_ADVISE in wrong postcopy "
+                   "state (%d)", ps);
         return -1;
     }
 
     switch (len) {
     case 0:
         if (migrate_postcopy_ram()) {
-            error_report("RAM postcopy is enabled but have 0 byte advise");
+            error_setg(errp, "RAM postcopy is enabled but have 0 byte advise");
             return -EINVAL;
         }
         return 0;
     case 8 + 8:
         if (!migrate_postcopy_ram()) {
-            error_report("RAM postcopy is disabled but have 16 byte advise");
+            error_setg(errp, "RAM postcopy is disabled but have 16 "
+                       "byte advise");
             return -EINVAL;
         }
         break;
     default:
-        error_report("CMD_POSTCOPY_ADVISE invalid length (%d)", len);
+        error_setg(errp, "CMD_POSTCOPY_ADVISE invalid length (%d)", len);
         return -EINVAL;
     }
 
-    if (!postcopy_ram_supported_by_host(mis, &local_err)) {
-        error_report_err(local_err);
+    if (!postcopy_ram_supported_by_host(mis, errp)) {
         postcopy_state_set(POSTCOPY_INCOMING_NONE);
         return -1;
     }
@@ -1961,9 +1961,9 @@ static int loadvm_postcopy_handle_advise(MigrationIncomingState *mis,
          *      also fails when passed to an older qemu that doesn't
          *      do huge pages.
          */
-        error_report("Postcopy needs matching RAM page sizes (s=%" PRIx64
-                                                             " d=%" PRIx64 ")",
-                     remote_pagesize_summary, local_pagesize_summary);
+        error_setg(errp, "Postcopy needs matching RAM "
+                   "page sizes (s=%" PRIx64 " d=%" PRIx64 ")",
+                   remote_pagesize_summary, local_pagesize_summary);
         return -1;
     }
 
@@ -1973,17 +1973,17 @@ static int loadvm_postcopy_handle_advise(MigrationIncomingState *mis,
          * Again, some differences could be dealt with, but for now keep it
          * simple.
          */
-        error_report("Postcopy needs matching target page sizes (s=%d d=%zd)",
-                     (int)remote_tps, page_size);
+        error_setg(errp, "Postcopy needs matching target "
+                   "page sizes (s=%d d=%zd)", (int)remote_tps, page_size);
         return -1;
     }
 
-    if (postcopy_notify(POSTCOPY_NOTIFY_INBOUND_ADVISE, &local_err)) {
-        error_report_err(local_err);
+    if (postcopy_notify(POSTCOPY_NOTIFY_INBOUND_ADVISE, errp)) {
         return -1;
     }
 
-    if (ram_postcopy_incoming_init(mis, NULL)) {
+    if (ram_postcopy_incoming_init(mis, errp)) {
+        error_prepend(errp, "PostCopy RAM incoming init failed ");
         return -1;
     }
 
@@ -2616,12 +2616,7 @@ static int loadvm_process_command(QEMUFile *f, Error **errp)
         return loadvm_handle_cmd_packaged(mis, errp);
 
     case MIG_CMD_POSTCOPY_ADVISE:
-        ret = loadvm_postcopy_handle_advise(mis, len);
-        if (ret < 0) {
-            error_setg(errp, "Failed to load device state command: %d", ret);
-            return -1;
-        }
-        return ret;
+        return loadvm_postcopy_handle_advise(mis, len, errp);
 
     case MIG_CMD_POSTCOPY_LISTEN:
         ret = loadvm_postcopy_handle_listen(mis);

-- 
2.50.0

[PATCH v5 11/23] migration: push Error **errp into loadvm_postcopy_handle_listen()

[Arun Menon]

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 loadvm_postcopy_handle_listen() must report an error
in errp, in case of failure.

Signed-off-by: Arun Menon <armenon@redhat.com>
---
 migration/savevm.c | 18 +++++++-----------
 1 file changed, 7 insertions(+), 11 deletions(-)

diff --git a/migration/savevm.c b/migration/savevm.c
index 608560af35dc76813bf6e9b571df3bd343f0eeab..a5ecec94482dfd23403d5b24e8e0c82d4cb73cc7 100644
--- a/migration/savevm.c
+++ b/migration/savevm.c
@@ -2173,15 +2173,16 @@ static void *postcopy_ram_listen_thread(void *opaque)
 }
 
 /* After this message we must be able to immediately receive postcopy data */
-static int loadvm_postcopy_handle_listen(MigrationIncomingState *mis)
+static int loadvm_postcopy_handle_listen(MigrationIncomingState *mis,
+                                         Error **errp)
 {
     PostcopyState ps = postcopy_state_set(POSTCOPY_INCOMING_LISTENING);
-    Error *local_err = NULL;
 
     trace_loadvm_postcopy_handle_listen("enter");
 
     if (ps != POSTCOPY_INCOMING_ADVISE && ps != POSTCOPY_INCOMING_DISCARD) {
-        error_report("CMD_POSTCOPY_LISTEN in wrong postcopy state (%d)", ps);
+        error_setg(errp, "CMD_POSTCOPY_LISTEN in wrong postcopy "
+                   "state (%d)", ps);
         return -1;
     }
     if (ps == POSTCOPY_INCOMING_ADVISE) {
@@ -2204,14 +2205,14 @@ static int loadvm_postcopy_handle_listen(MigrationIncomingState *mis)
     if (migrate_postcopy_ram()) {
         if (postcopy_ram_incoming_setup(mis)) {
             postcopy_ram_incoming_cleanup(mis);
+            error_setg(errp, "Failed to setup incoming postcopy RAM blocks");
             return -1;
         }
     }
 
     trace_loadvm_postcopy_handle_listen("after uffd");
 
-    if (postcopy_notify(POSTCOPY_NOTIFY_INBOUND_LISTEN, &local_err)) {
-        error_report_err(local_err);
+    if (postcopy_notify(POSTCOPY_NOTIFY_INBOUND_LISTEN, errp)) {
         return -1;
     }
 
@@ -2619,12 +2620,7 @@ static int loadvm_process_command(QEMUFile *f, Error **errp)
         return loadvm_postcopy_handle_advise(mis, len, errp);
 
     case MIG_CMD_POSTCOPY_LISTEN:
-        ret = loadvm_postcopy_handle_listen(mis);
-        if (ret < 0) {
-            error_setg(errp, "Failed to load device state command: %d", ret);
-            return -1;
-        }
-        return ret;
+        return loadvm_postcopy_handle_listen(mis, errp);
 
     case MIG_CMD_POSTCOPY_RUN:
         ret = loadvm_postcopy_handle_run(mis);

-- 
2.50.0

[PATCH v5 12/23] migration: push Error **errp into loadvm_postcopy_handle_run()

[Arun Menon]

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 loadvm_postcopy_handle_run() must report an error
in errp, in case of failure.

Signed-off-by: Arun Menon <armenon@redhat.com>
---
 migration/savevm.c | 12 ++++--------
 1 file changed, 4 insertions(+), 8 deletions(-)

diff --git a/migration/savevm.c b/migration/savevm.c
index a5ecec94482dfd23403d5b24e8e0c82d4cb73cc7..509b71dc2666617ee3e7b707f46187ee5287d201 100644
--- a/migration/savevm.c
+++ b/migration/savevm.c
@@ -2265,13 +2265,14 @@ static void loadvm_postcopy_handle_run_bh(void *opaque)
 }
 
 /* After all discards we can start running and asking for pages */
-static int loadvm_postcopy_handle_run(MigrationIncomingState *mis)
+static int loadvm_postcopy_handle_run(MigrationIncomingState *mis, Error **errp)
 {
     PostcopyState ps = postcopy_state_get();
 
     trace_loadvm_postcopy_handle_run();
     if (ps != POSTCOPY_INCOMING_LISTENING) {
-        error_report("CMD_POSTCOPY_RUN in wrong postcopy state (%d)", ps);
+        error_setg(errp, "CMD_POSTCOPY_RUN in wrong postcopy "
+                   "state (%d)", ps);
         return -1;
     }
 
@@ -2623,12 +2624,7 @@ static int loadvm_process_command(QEMUFile *f, Error **errp)
         return loadvm_postcopy_handle_listen(mis, errp);
 
     case MIG_CMD_POSTCOPY_RUN:
-        ret = loadvm_postcopy_handle_run(mis);
-        if (ret < 0) {
-            error_setg(errp, "Failed to load device state command: %d", ret);
-            return -1;
-        }
-        return ret;
+        return loadvm_postcopy_handle_run(mis, errp);
 
     case MIG_CMD_POSTCOPY_RAM_DISCARD:
         ret = loadvm_postcopy_ram_handle_discard(mis, len);

-- 
2.50.0

[PATCH v5 13/23] migration: push Error **errp into loadvm_postcopy_ram_handle_discard()

[Arun Menon]

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 loadvm_postcopy_ram_handle_discard() must report an error
in errp, in case of failure.

Signed-off-by: Arun Menon <armenon@redhat.com>
---
 migration/savevm.c | 26 ++++++++++++--------------
 1 file changed, 12 insertions(+), 14 deletions(-)

diff --git a/migration/savevm.c b/migration/savevm.c
index 509b71dc2666617ee3e7b707f46187ee5287d201..6f181c381dc6ecd996a1f8dbc25cceead7ebe014 100644
--- a/migration/savevm.c
+++ b/migration/savevm.c
@@ -1996,7 +1996,7 @@ static int loadvm_postcopy_handle_advise(MigrationIncomingState *mis,
  * There can be 0..many of these messages, each encoding multiple pages.
  */
 static int loadvm_postcopy_ram_handle_discard(MigrationIncomingState *mis,
-                                              uint16_t len)
+                                              uint16_t len, Error **errp)
 {
     int tmp;
     char ramid[256];
@@ -2009,6 +2009,7 @@ static int loadvm_postcopy_ram_handle_discard(MigrationIncomingState *mis,
         /* 1st discard */
         tmp = postcopy_ram_prepare_discard(mis);
         if (tmp) {
+            error_setg(errp, "Failed to prepare for RAM discard: %d", tmp);
             return tmp;
         }
         break;
@@ -2018,8 +2019,8 @@ static int loadvm_postcopy_ram_handle_discard(MigrationIncomingState *mis,
         break;
 
     default:
-        error_report("CMD_POSTCOPY_RAM_DISCARD in wrong postcopy state (%d)",
-                     ps);
+        error_setg(errp, "CMD_POSTCOPY_RAM_DISCARD in wrong "
+                   "postcopy state (%d)", ps);
         return -1;
     }
     /* We're expecting a
@@ -2028,29 +2029,30 @@ static int loadvm_postcopy_ram_handle_discard(MigrationIncomingState *mis,
      *    then at least 1 16 byte chunk
     */
     if (len < (1 + 1 + 1 + 1 + 2 * 8)) {
-        error_report("CMD_POSTCOPY_RAM_DISCARD invalid length (%d)", len);
+        error_setg(errp, "CMD_POSTCOPY_RAM_DISCARD invalid length (%d)", len);
         return -1;
     }
 
     tmp = qemu_get_byte(mis->from_src_file);
     if (tmp != postcopy_ram_discard_version) {
-        error_report("CMD_POSTCOPY_RAM_DISCARD invalid version (%d)", tmp);
+        error_setg(errp, "CMD_POSTCOPY_RAM_DISCARD invalid version (%d)", tmp);
         return -1;
     }
 
     if (!qemu_get_counted_string(mis->from_src_file, ramid)) {
-        error_report("CMD_POSTCOPY_RAM_DISCARD Failed to read RAMBlock ID");
+        error_setg(errp, "CMD_POSTCOPY_RAM_DISCARD Failed to read "
+                   "RAMBlock ID");
         return -1;
     }
     tmp = qemu_get_byte(mis->from_src_file);
     if (tmp != 0) {
-        error_report("CMD_POSTCOPY_RAM_DISCARD missing nil (%d)", tmp);
+        error_setg(errp, "CMD_POSTCOPY_RAM_DISCARD missing nil (%d)", tmp);
         return -1;
     }
 
     len -= 3 + strlen(ramid);
     if (len % 16) {
-        error_report("CMD_POSTCOPY_RAM_DISCARD invalid length (%d)", len);
+        error_setg(errp, "CMD_POSTCOPY_RAM_DISCARD invalid length (%d)", len);
         return -1;
     }
     trace_loadvm_postcopy_ram_handle_discard_header(ramid, len);
@@ -2062,6 +2064,7 @@ static int loadvm_postcopy_ram_handle_discard(MigrationIncomingState *mis,
         len -= 16;
         int ret = ram_discard_range(ramid, start_addr, block_length);
         if (ret) {
+            error_setg(errp, "Failed to discard RAM range %s: %d", ramid, ret);
             return ret;
         }
     }
@@ -2627,12 +2630,7 @@ static int loadvm_process_command(QEMUFile *f, Error **errp)
         return loadvm_postcopy_handle_run(mis, errp);
 
     case MIG_CMD_POSTCOPY_RAM_DISCARD:
-        ret = loadvm_postcopy_ram_handle_discard(mis, len);
-        if (ret < 0) {
-            error_setg(errp, "Failed to load device state command: %d", ret);
-            return -1;
-        }
-        return ret;
+        return loadvm_postcopy_ram_handle_discard(mis, len, errp);
 
     case MIG_CMD_POSTCOPY_RESUME:
         ret = loadvm_postcopy_handle_resume(mis);

-- 
2.50.0

[PATCH v5 14/23] migration: make loadvm_postcopy_handle_resume() void

[Arun Menon]

This is an incremental step in converting vmstate loading
code to report error via Error objects instead of directly
printing it to console/monitor.

Signed-off-by: Arun Menon <armenon@redhat.com>
---
 migration/savevm.c | 14 ++++----------
 1 file changed, 4 insertions(+), 10 deletions(-)

diff --git a/migration/savevm.c b/migration/savevm.c
index 6f181c381dc6ecd996a1f8dbc25cceead7ebe014..20dce4b43a181d2f47b6b22e7a15aa4fc45cac5c 100644
--- a/migration/savevm.c
+++ b/migration/savevm.c
@@ -2333,12 +2333,12 @@ static void migrate_send_rp_req_pages_pending(MigrationIncomingState *mis)
     }
 }
 
-static int loadvm_postcopy_handle_resume(MigrationIncomingState *mis)
+static void loadvm_postcopy_handle_resume(MigrationIncomingState *mis)
 {
     if (mis->state != MIGRATION_STATUS_POSTCOPY_RECOVER) {
         error_report("%s: illegal resume received", __func__);
         /* Don't fail the load, only for this. */
-        return 0;
+        return;
     }
 
     /*
@@ -2390,8 +2390,6 @@ static int loadvm_postcopy_handle_resume(MigrationIncomingState *mis)
         /* Kick the fast ram load thread too */
         qemu_sem_post(&mis->postcopy_pause_sem_fast_load);
     }
-
-    return 0;
 }
 
 /**
@@ -2633,12 +2631,8 @@ static int loadvm_process_command(QEMUFile *f, Error **errp)
         return loadvm_postcopy_ram_handle_discard(mis, len, errp);
 
     case MIG_CMD_POSTCOPY_RESUME:
-        ret = loadvm_postcopy_handle_resume(mis);
-        if (ret < 0) {
-            error_setg(errp, "Failed to load device state command: %d", ret);
-            return -1;
-        }
-        return ret;
+        loadvm_postcopy_handle_resume(mis);
+        return 0;
 
     case MIG_CMD_RECV_BITMAP:
         ret = loadvm_handle_recv_bitmap(mis, len);

-- 
2.50.0

[PATCH v5 15/23] migration: push Error **errp into loadvm_handle_recv_bitmap()

[Arun Menon]

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 loadvm_handle_recv_bitmap() must report an error
in errp, in case of failure.

Signed-off-by: Arun Menon <armenon@redhat.com>
---
 migration/savevm.c | 22 ++++++++++------------
 1 file changed, 10 insertions(+), 12 deletions(-)

diff --git a/migration/savevm.c b/migration/savevm.c
index 20dce4b43a181d2f47b6b22e7a15aa4fc45cac5c..1cbc44a5314043a403d983511066cf137681a18d 100644
--- a/migration/savevm.c
+++ b/migration/savevm.c
@@ -2471,32 +2471,35 @@ static int loadvm_handle_cmd_packaged(MigrationIncomingState *mis, Error **errp)
  * len (1 byte) + ramblock_name (<255 bytes)
  */
 static int loadvm_handle_recv_bitmap(MigrationIncomingState *mis,
-                                     uint16_t len)
+                                     uint16_t len, Error **errp)
 {
     QEMUFile *file = mis->from_src_file;
     RAMBlock *rb;
     char block_name[256];
     size_t cnt;
+    int ret;
 
     cnt = qemu_get_counted_string(file, block_name);
     if (!cnt) {
-        error_report("%s: failed to read block name", __func__);
+        error_setg(errp, "%s: failed to read block name", __func__);
         return -EINVAL;
     }
 
     /* Validate before using the data */
-    if (qemu_file_get_error(file)) {
-        return qemu_file_get_error(file);
+    ret = qemu_file_get_error(file);
+    if (ret < 0) {
+        error_setg(errp, "migration stream has error: %d", ret);
+        return ret;
     }
 
     if (len != cnt + 1) {
-        error_report("%s: invalid payload length (%d)", __func__, len);
+        error_setg(errp, "%s: invalid payload length (%d)", __func__, len);
         return -EINVAL;
     }
 
     rb = qemu_ram_block_by_name(block_name);
     if (!rb) {
-        error_report("%s: block '%s' not found", __func__, block_name);
+        error_setg(errp, "%s: block '%s' not found", __func__, block_name);
         return -EINVAL;
     }
 
@@ -2635,12 +2638,7 @@ static int loadvm_process_command(QEMUFile *f, Error **errp)
         return 0;
 
     case MIG_CMD_RECV_BITMAP:
-        ret = loadvm_handle_recv_bitmap(mis, len);
-        if (ret < 0) {
-            error_setg(errp, "Failed to load device state command: %d", ret);
-            return -1;
-        }
-        return ret;
+        return loadvm_handle_recv_bitmap(mis, len, errp);
 
     case MIG_CMD_ENABLE_COLO:
         ret = loadvm_process_enable_colo(mis);

-- 
2.50.0

[PATCH v5 16/23] migration: push Error **errp into loadvm_process_enable_colo()

[Arun Menon]

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 loadvm_process_enable_colo() must report an error
in errp, in case of failure.

Signed-off-by: Arun Menon <armenon@redhat.com>
---
 include/migration/colo.h |  2 +-
 migration/migration.c    | 12 ++++++------
 migration/ram.c          |  8 ++++----
 migration/ram.h          |  2 +-
 migration/savevm.c       | 25 ++++++++++++-------------
 5 files changed, 24 insertions(+), 25 deletions(-)

diff --git a/include/migration/colo.h b/include/migration/colo.h
index 43222ef5ae6adc3f7d8aa6a48bef79af33d09208..d4fe422e4d335d3bef4f860f56400fcd73287a0e 100644
--- a/include/migration/colo.h
+++ b/include/migration/colo.h
@@ -25,7 +25,7 @@ void migrate_start_colo_process(MigrationState *s);
 bool migration_in_colo_state(void);
 
 /* loadvm */
-int migration_incoming_enable_colo(void);
+int migration_incoming_enable_colo(Error **errp);
 void migration_incoming_disable_colo(void);
 bool migration_incoming_colo_enabled(void);
 bool migration_incoming_in_colo_state(void);
diff --git a/migration/migration.c b/migration/migration.c
index 10c216d25dec01f206eacad2edd24d21f00e614c..326487882c8d41e2f89f99f69df0d9d4d42705e4 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -623,22 +623,22 @@ void migration_incoming_disable_colo(void)
     migration_colo_enabled = false;
 }
 
-int migration_incoming_enable_colo(void)
+int migration_incoming_enable_colo(Error **errp)
 {
 #ifndef CONFIG_REPLICATION
-    error_report("ENABLE_COLO command come in migration stream, but the "
-                 "replication module is not built in");
+    error_setg(errp, "ENABLE_COLO command come in migration stream, but the "
+               "replication module is not built in");
     return -ENOTSUP;
 #endif
 
     if (!migrate_colo()) {
-        error_report("ENABLE_COLO command come in migration stream, but x-colo "
-                     "capability is not set");
+        error_setg(errp, "ENABLE_COLO command come in migration stream"
+                   ", but x-colo capability is not set");
         return -EINVAL;
     }
 
     if (ram_block_discard_disable(true)) {
-        error_report("COLO: cannot disable RAM discard");
+        error_setg(errp, "COLO: cannot disable RAM discard");
         return -EBUSY;
     }
     migration_colo_enabled = true;
diff --git a/migration/ram.c b/migration/ram.c
index 8223183132dc0f558f45fbae3f4f832845730bd3..607c979cc15a3d321e5e3e380ac7613d80d86fc9 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -3576,7 +3576,7 @@ static void colo_init_ram_state(void)
  * memory of the secondary VM, it is need to hold the global lock
  * to call this helper.
  */
-int colo_init_ram_cache(void)
+int colo_init_ram_cache(Error **errp)
 {
     RAMBlock *block;
 
@@ -3585,9 +3585,9 @@ int colo_init_ram_cache(void)
             block->colo_cache = qemu_anon_ram_alloc(block->used_length,
                                                     NULL, false, false);
             if (!block->colo_cache) {
-                error_report("%s: Can't alloc memory for COLO cache of block %s,"
-                             "size 0x" RAM_ADDR_FMT, __func__, block->idstr,
-                             block->used_length);
+                error_setg(errp, "%s: Can't alloc memory for COLO cache of "
+                           "block %s, size 0x" RAM_ADDR_FMT, __func__,
+                           block->idstr, block->used_length);
                 RAMBLOCK_FOREACH_NOT_IGNORED(block) {
                     if (block->colo_cache) {
                         qemu_anon_ram_free(block->colo_cache, block->used_length);
diff --git a/migration/ram.h b/migration/ram.h
index 275709a99187f9429ccb4111e05281ec268ba0db..24cd0bf585762cfa1e86834dc03c6baeea2f0627 100644
--- a/migration/ram.h
+++ b/migration/ram.h
@@ -109,7 +109,7 @@ void ramblock_set_file_bmap_atomic(RAMBlock *block, ram_addr_t offset,
                                    bool set);
 
 /* ram cache */
-int colo_init_ram_cache(void);
+int colo_init_ram_cache(Error **errp);
 void colo_flush_ram_cache(void);
 void colo_release_ram_cache(void);
 void colo_incoming_start_dirty_log(void);
diff --git a/migration/savevm.c b/migration/savevm.c
index 1cbc44a5314043a403d983511066cf137681a18d..755ba7e4504d377a4649da191ad9875d9fd66f69 100644
--- a/migration/savevm.c
+++ b/migration/savevm.c
@@ -2510,15 +2510,19 @@ static int loadvm_handle_recv_bitmap(MigrationIncomingState *mis,
     return 0;
 }
 
-static int loadvm_process_enable_colo(MigrationIncomingState *mis)
+static int loadvm_process_enable_colo(MigrationIncomingState *mis,
+                                      Error **errp)
 {
-    int ret = migration_incoming_enable_colo();
+    int ret;
 
-    if (!ret) {
-        ret = colo_init_ram_cache();
-        if (ret) {
-            migration_incoming_disable_colo();
-        }
+    if (migration_incoming_enable_colo(errp) < 0) {
+        return -1;
+    }
+
+    ret = colo_init_ram_cache(errp);
+    if (ret) {
+        error_prepend(errp, "failed to init colo RAM cache: %d", ret);
+        migration_incoming_disable_colo();
     }
     return ret;
 }
@@ -2641,12 +2645,7 @@ static int loadvm_process_command(QEMUFile *f, Error **errp)
         return loadvm_handle_recv_bitmap(mis, len, errp);
 
     case MIG_CMD_ENABLE_COLO:
-        ret = loadvm_process_enable_colo(mis);
-        if (ret < 0) {
-            error_setg(errp, "Failed to load device state command: %d", ret);
-            return -1;
-        }
-        return ret;
+        return loadvm_process_enable_colo(mis, errp);
 
     case MIG_CMD_SWITCHOVER_START:
         ret = loadvm_postcopy_handle_switchover_start();

-- 
2.50.0

[PATCH v5 17/23] migration: push Error **errp into loadvm_postcopy_handle_switchover_start()

[Arun Menon]

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 loadvm_postcopy_handle_switchover_start() must report
an error in errp, in case of failure.

Signed-off-by: Arun Menon <armenon@redhat.com>
---
 migration/savevm.c | 10 +++-------
 1 file changed, 3 insertions(+), 7 deletions(-)

diff --git a/migration/savevm.c b/migration/savevm.c
index 755ba7e4504d377a4649da191ad9875d9fd66f69..a23c242a5f05f85a8544924c464480810995815e 100644
--- a/migration/savevm.c
+++ b/migration/savevm.c
@@ -2527,7 +2527,7 @@ static int loadvm_process_enable_colo(MigrationIncomingState *mis,
     return ret;
 }
 
-static int loadvm_postcopy_handle_switchover_start(void)
+static int loadvm_postcopy_handle_switchover_start(Error **errp)
 {
     SaveStateEntry *se;
 
@@ -2540,6 +2540,7 @@ static int loadvm_postcopy_handle_switchover_start(void)
 
         ret = se->ops->switchover_start(se->opaque);
         if (ret < 0) {
+            error_setg(errp, "Switchover start failed: %d", ret);
             return ret;
         }
     }
@@ -2648,12 +2649,7 @@ static int loadvm_process_command(QEMUFile *f, Error **errp)
         return loadvm_process_enable_colo(mis, errp);
 
     case MIG_CMD_SWITCHOVER_START:
-        ret = loadvm_postcopy_handle_switchover_start();
-        if (ret < 0) {
-            error_setg(errp, "Failed to load device state command: %d", ret);
-            return -1;
-        }
-        return ret;
+        return loadvm_postcopy_handle_switchover_start(errp);
     }
 
     return 0;

-- 
2.50.0

[PATCH v5 18/23] migration: push Error **errp into qemu_loadvm_state_main()

[Arun Menon]

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 qemu_loadvm_state_main() must report an error
in errp, in case of failure.
loadvm_process_command also sets the errp object explicitly.

Signed-off-by: Arun Menon <armenon@redhat.com>
---
 migration/colo.c   |  5 +++--
 migration/savevm.c | 23 +++++++++++++----------
 migration/savevm.h |  3 ++-
 3 files changed, 18 insertions(+), 13 deletions(-)

diff --git a/migration/colo.c b/migration/colo.c
index e0f713c837f5da25d67afbd02ceb6c54024ca3af..ddc628cab4194b3cb82388c5e878286c820004b2 100644
--- a/migration/colo.c
+++ b/migration/colo.c
@@ -686,11 +686,12 @@ static void colo_incoming_process_checkpoint(MigrationIncomingState *mis,
 
     bql_lock();
     cpu_synchronize_all_states();
-    ret = qemu_loadvm_state_main(mis->from_src_file, mis);
+    ret = qemu_loadvm_state_main(mis->from_src_file, mis, &local_err);
     bql_unlock();
 
     if (ret < 0) {
-        error_setg(errp, "Load VM's live state (ram) error");
+        error_propagate_prepend(errp, local_err,
+                                "Load VM's live state (ram) error");
         return;
     }
 
diff --git a/migration/savevm.c b/migration/savevm.c
index a23c242a5f05f85a8544924c464480810995815e..47c656734248c2b7a6d2001c6ef9b3e83af11bac 100644
--- a/migration/savevm.c
+++ b/migration/savevm.c
@@ -2102,7 +2102,7 @@ static void *postcopy_ram_listen_thread(void *opaque)
     qemu_file_set_blocking(f, true);
 
     /* TODO: sanity check that only postcopiable data will be loaded here */
-    load_res = qemu_loadvm_state_main(f, mis);
+    load_res = qemu_loadvm_state_main(f, mis, NULL);
 
     /*
      * This is tricky, but, mis->from_src_file can change after it
@@ -2453,9 +2453,9 @@ static int loadvm_handle_cmd_packaged(MigrationIncomingState *mis, Error **errp)
         qemu_coroutine_yield();
     } while (1);
 
-    ret = qemu_loadvm_state_main(packf, mis);
+    ret = qemu_loadvm_state_main(packf, mis, errp);
     if (ret < 0) {
-        error_setg(errp, "VM state load failed: %d", ret);
+        error_prepend(errp, "Loading VM state failed: %d ", ret);
     }
     trace_loadvm_handle_cmd_packaged_main(ret);
     qemu_fclose(packf);
@@ -3055,7 +3055,8 @@ static bool postcopy_pause_incoming(MigrationIncomingState *mis)
     return true;
 }
 
-int qemu_loadvm_state_main(QEMUFile *f, MigrationIncomingState *mis)
+int qemu_loadvm_state_main(QEMUFile *f, MigrationIncomingState *mis,
+                           Error **errp)
 {
     uint8_t section_type;
     int ret = 0;
@@ -3066,6 +3067,8 @@ retry:
 
         ret = qemu_file_get_error_obj_any(f, mis->postcopy_qemufile_dst, NULL);
         if (ret) {
+            error_setg(errp, "Failed to load device state section ID : %d",
+                       ret);
             break;
         }
 
@@ -3073,20 +3076,20 @@ retry:
         switch (section_type) {
         case QEMU_VM_SECTION_START:
         case QEMU_VM_SECTION_FULL:
-            ret = qemu_loadvm_section_start_full(f, section_type, NULL);
+            ret = qemu_loadvm_section_start_full(f, section_type, errp);
             if (ret < 0) {
                 goto out;
             }
             break;
         case QEMU_VM_SECTION_PART:
         case QEMU_VM_SECTION_END:
-            ret = qemu_loadvm_section_part_end(f, section_type, NULL);
+            ret = qemu_loadvm_section_part_end(f, section_type, errp);
             if (ret < 0) {
                 goto out;
             }
             break;
         case QEMU_VM_COMMAND:
-            ret = loadvm_process_command(f, NULL);
+            ret = loadvm_process_command(f, errp);
             trace_qemu_loadvm_state_section_command(ret);
             if ((ret < 0) || (ret == LOADVM_QUIT)) {
                 goto out;
@@ -3096,7 +3099,7 @@ retry:
             /* This is the end of migration */
             goto out;
         default:
-            error_report("Unknown savevm section type %d", section_type);
+            error_setg(errp, "Unknown savevm section type %d", section_type);
             ret = -EINVAL;
             goto out;
         }
@@ -3160,7 +3163,7 @@ int qemu_loadvm_state(QEMUFile *f)
 
     cpu_synchronize_all_pre_loadvm();
 
-    ret = qemu_loadvm_state_main(f, mis);
+    ret = qemu_loadvm_state_main(f, mis, NULL);
     qemu_event_set(&mis->main_thread_load_event);
 
     trace_qemu_loadvm_state_post_main(ret);
@@ -3234,7 +3237,7 @@ int qemu_load_device_state(QEMUFile *f)
     int ret;
 
     /* Load QEMU_VM_SECTION_FULL section */
-    ret = qemu_loadvm_state_main(f, mis);
+    ret = qemu_loadvm_state_main(f, mis, NULL);
     if (ret < 0) {
         error_report("Failed to load device state: %d", ret);
         return ret;
diff --git a/migration/savevm.h b/migration/savevm.h
index 2d5e9c716686f06720325e82fe90c75335ced1de..fd7419e6ff90062970ed246b3ea71e6d49a6e372 100644
--- a/migration/savevm.h
+++ b/migration/savevm.h
@@ -66,7 +66,8 @@ int qemu_save_device_state(QEMUFile *f);
 
 int qemu_loadvm_state(QEMUFile *f);
 void qemu_loadvm_state_cleanup(MigrationIncomingState *mis);
-int qemu_loadvm_state_main(QEMUFile *f, MigrationIncomingState *mis);
+int qemu_loadvm_state_main(QEMUFile *f, MigrationIncomingState *mis,
+                           Error **errp);
 int qemu_load_device_state(QEMUFile *f);
 int qemu_loadvm_approve_switchover(void);
 int qemu_savevm_state_complete_precopy_non_iterable(QEMUFile *f,

-- 
2.50.0

[PATCH v5 19/23] migration: push Error **errp into qemu_loadvm_state()

[Arun Menon]

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 qemu_loadvm_state() must report an error
in errp, in case of failure.

Signed-off-by: Arun Menon <armenon@redhat.com>
---
 migration/migration.c |  5 +++--
 migration/savevm.c    | 25 +++++++++++++------------
 migration/savevm.h    |  2 +-
 3 files changed, 17 insertions(+), 15 deletions(-)

diff --git a/migration/migration.c b/migration/migration.c
index 326487882c8d41e2f89f99f69df0d9d4d42705e4..1f0a8bd6ab28ff09bb76919564bdbfbde35c5e42 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -881,7 +881,7 @@ process_incoming_migration_co(void *opaque)
                       MIGRATION_STATUS_ACTIVE);
 
     mis->loadvm_co = qemu_coroutine_self();
-    ret = qemu_loadvm_state(mis->from_src_file);
+    ret = qemu_loadvm_state(mis->from_src_file, &local_err);
     mis->loadvm_co = NULL;
 
     trace_vmstate_downtime_checkpoint("dst-precopy-loadvm-completed");
@@ -908,7 +908,8 @@ process_incoming_migration_co(void *opaque)
     }
 
     if (ret < 0) {
-        error_setg(&local_err, "load of migration failed: %s", strerror(-ret));
+        error_prepend(&local_err, "load of migration failed: %s ",
+                      strerror(-ret));
         goto fail;
     }
 
diff --git a/migration/savevm.c b/migration/savevm.c
index 47c656734248c2b7a6d2001c6ef9b3e83af11bac..ea64603b75ead17bcc21aebfa49ede3991387fb7 100644
--- a/migration/savevm.c
+++ b/migration/savevm.c
@@ -3133,27 +3133,24 @@ out:
     return ret;
 }
 
-int qemu_loadvm_state(QEMUFile *f)
+int qemu_loadvm_state(QEMUFile *f, Error **errp)
 {
     MigrationState *s = migrate_get_current();
     MigrationIncomingState *mis = migration_incoming_get_current();
-    Error *local_err = NULL;
     int ret;
 
-    if (qemu_savevm_state_blocked(&local_err)) {
-        error_report_err(local_err);
+    if (qemu_savevm_state_blocked(errp)) {
         return -EINVAL;
     }
 
     qemu_loadvm_thread_pool_create(mis);
 
-    ret = qemu_loadvm_state_header(f, NULL);
+    ret = qemu_loadvm_state_header(f, errp);
     if (ret) {
         return ret;
     }
 
-    if (qemu_loadvm_state_setup(f, &local_err) != 0) {
-        error_report_err(local_err);
+    if (qemu_loadvm_state_setup(f, errp) != 0) {
         return -EINVAL;
     }
 
@@ -3163,7 +3160,7 @@ int qemu_loadvm_state(QEMUFile *f)
 
     cpu_synchronize_all_pre_loadvm();
 
-    ret = qemu_loadvm_state_main(f, mis, NULL);
+    ret = qemu_loadvm_state_main(f, mis, errp);
     qemu_event_set(&mis->main_thread_load_event);
 
     trace_qemu_loadvm_state_post_main(ret);
@@ -3181,8 +3178,12 @@ int qemu_loadvm_state(QEMUFile *f)
         if (migrate_has_error(migrate_get_current()) ||
             !qemu_loadvm_thread_pool_wait(s, mis)) {
             ret = -EINVAL;
+            error_setg(errp, "Error while loading vmstate : %d", ret);
         } else {
             ret = qemu_file_get_error(f);
+            if (ret < 0) {
+                error_setg(errp, "Error while loading vmstate : %d", ret);
+            }
         }
     }
     /*
@@ -3468,10 +3469,10 @@ void qmp_xen_load_devices_state(const char *filename, Error **errp)
     f = qemu_file_new_input(QIO_CHANNEL(ioc));
     object_unref(OBJECT(ioc));
 
-    ret = qemu_loadvm_state(f);
+    ret = qemu_loadvm_state(f, errp);
     qemu_fclose(f);
     if (ret < 0) {
-        error_setg(errp, "loading Xen device state failed");
+        error_prepend(errp, "loading Xen device state failed ");
     }
     migration_incoming_state_destroy();
 }
@@ -3542,13 +3543,13 @@ bool load_snapshot(const char *name, const char *vmstate,
         ret = -EINVAL;
         goto err_drain;
     }
-    ret = qemu_loadvm_state(f);
+    ret = qemu_loadvm_state(f, errp);
     migration_incoming_state_destroy();
 
     bdrv_drain_all_end();
 
     if (ret < 0) {
-        error_setg(errp, "Error %d while loading VM state", ret);
+        error_prepend(errp, "Error %d while loading VM state ", ret);
         return false;
     }
 
diff --git a/migration/savevm.h b/migration/savevm.h
index fd7419e6ff90062970ed246b3ea71e6d49a6e372..a6df5198f3fe1a39fc0e6ce3e79cf7a5d8e032db 100644
--- a/migration/savevm.h
+++ b/migration/savevm.h
@@ -64,7 +64,7 @@ void qemu_savevm_send_colo_enable(QEMUFile *f);
 void qemu_savevm_live_state(QEMUFile *f);
 int qemu_save_device_state(QEMUFile *f);
 
-int qemu_loadvm_state(QEMUFile *f);
+int qemu_loadvm_state(QEMUFile *f, Error **errp);
 void qemu_loadvm_state_cleanup(MigrationIncomingState *mis);
 int qemu_loadvm_state_main(QEMUFile *f, MigrationIncomingState *mis,
                            Error **errp);

-- 
2.50.0

[PATCH v5 20/23] migration: push Error **errp into qemu_load_device_state()

[Arun Menon]

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 qemu_load_device_state() must report an error
in errp, in case of failure.

Signed-off-by: Arun Menon <armenon@redhat.com>
---
 migration/colo.c   | 5 +++--
 migration/savevm.c | 6 +++---
 migration/savevm.h | 2 +-
 3 files changed, 7 insertions(+), 6 deletions(-)

diff --git a/migration/colo.c b/migration/colo.c
index ddc628cab4194b3cb82388c5e878286c820004b2..7291df0d47d8e308f8b71973c908b5a05ec7f4d7 100644
--- a/migration/colo.c
+++ b/migration/colo.c
@@ -730,9 +730,10 @@ static void colo_incoming_process_checkpoint(MigrationIncomingState *mis,
     bql_lock();
     vmstate_loading = true;
     colo_flush_ram_cache();
-    ret = qemu_load_device_state(fb);
+    ret = qemu_load_device_state(fb, &local_err);
     if (ret < 0) {
-        error_setg(errp, "COLO: load device state failed");
+        error_propagate_prepend(errp, local_err,
+                                "COLO: load device state failed");
         vmstate_loading = false;
         bql_unlock();
         return;
diff --git a/migration/savevm.c b/migration/savevm.c
index ea64603b75ead17bcc21aebfa49ede3991387fb7..0fff65c96344c65191353311e72730cd6e3bfb23 100644
--- a/migration/savevm.c
+++ b/migration/savevm.c
@@ -3232,15 +3232,15 @@ int qemu_loadvm_state(QEMUFile *f, Error **errp)
     return ret;
 }
 
-int qemu_load_device_state(QEMUFile *f)
+int qemu_load_device_state(QEMUFile *f, Error **errp)
 {
     MigrationIncomingState *mis = migration_incoming_get_current();
     int ret;
 
     /* Load QEMU_VM_SECTION_FULL section */
-    ret = qemu_loadvm_state_main(f, mis, NULL);
+    ret = qemu_loadvm_state_main(f, mis, errp);
     if (ret < 0) {
-        error_report("Failed to load device state: %d", ret);
+        error_prepend(errp, "Failed to load device state: %d ", ret);
         return ret;
     }
 
diff --git a/migration/savevm.h b/migration/savevm.h
index a6df5198f3fe1a39fc0e6ce3e79cf7a5d8e032db..c337e3e3d111a7f28a57b90f61e8f70b71803d4e 100644
--- a/migration/savevm.h
+++ b/migration/savevm.h
@@ -68,7 +68,7 @@ int qemu_loadvm_state(QEMUFile *f, Error **errp);
 void qemu_loadvm_state_cleanup(MigrationIncomingState *mis);
 int qemu_loadvm_state_main(QEMUFile *f, MigrationIncomingState *mis,
                            Error **errp);
-int qemu_load_device_state(QEMUFile *f);
+int qemu_load_device_state(QEMUFile *f, Error **errp);
 int qemu_loadvm_approve_switchover(void);
 int qemu_savevm_state_complete_precopy_non_iterable(QEMUFile *f,
         bool in_postcopy);

-- 
2.50.0

[PATCH v5 21/23] migration: Capture error in postcopy_ram_listen_thread()

[Arun Menon]

This is an incremental step in converting vmstate loading
code to report error via Error objects instead of directly
printing it to console/monitor.
postcopy_ram_listen_thread() calls qemu_loadvm_state_main()
to load the vm, and in case of a failure, it should set the error
in the migration object.

When postcopy live migration runs, the device states are loaded by
both the qemu coroutine process_incoming_migration_co() and the
postcopy_ram_listen_thread(). Therefore, it is important that the
coroutine also reports the error in case of failure, with
error_report_err(). Otherwise, the source qemu will not display
any errors before going into the postcopy pause state.

Signed-off-by: Arun Menon <armenon@redhat.com>
---
 migration/migration.c |  2 +-
 migration/savevm.c    | 10 ++++++++--
 2 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/migration/migration.c b/migration/migration.c
index 1f0a8bd6ab28ff09bb76919564bdbfbde35c5e42..efd02d917cfe4d1221907123eadd98932b02e8bc 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -925,7 +925,7 @@ fail:
     migrate_set_state(&mis->state, MIGRATION_STATUS_ACTIVE,
                       MIGRATION_STATUS_FAILED);
     migrate_set_error(s, local_err);
-    error_free(local_err);
+    error_report_err(local_err);
 
     migration_incoming_state_destroy();
 
diff --git a/migration/savevm.c b/migration/savevm.c
index 0fff65c96344c65191353311e72730cd6e3bfb23..4f67eebe5321c175d51e8029e36ceb336c98ad1f 100644
--- a/migration/savevm.c
+++ b/migration/savevm.c
@@ -2086,6 +2086,7 @@ static void *postcopy_ram_listen_thread(void *opaque)
     QEMUFile *f = mis->from_src_file;
     int load_res;
     MigrationState *migr = migrate_get_current();
+    Error *local_err = NULL;
 
     object_ref(OBJECT(migr));
 
@@ -2102,7 +2103,7 @@ static void *postcopy_ram_listen_thread(void *opaque)
     qemu_file_set_blocking(f, true);
 
     /* TODO: sanity check that only postcopiable data will be loaded here */
-    load_res = qemu_loadvm_state_main(f, mis, NULL);
+    load_res = qemu_loadvm_state_main(f, mis, &local_err);
 
     /*
      * This is tricky, but, mis->from_src_file can change after it
@@ -2128,7 +2129,12 @@ static void *postcopy_ram_listen_thread(void *opaque)
                          __func__, load_res);
             load_res = 0; /* prevent further exit() */
         } else {
-            error_report("%s: loadvm failed: %d", __func__, load_res);
+            if (local_err != NULL) {
+                error_prepend(&local_err, "%s: loadvm failed: %d", __func__,
+                              load_res);
+                migrate_set_error(migr, local_err);
+                error_report_err(local_err);
+            }
             migrate_set_state(&mis->state, MIGRATION_STATUS_POSTCOPY_ACTIVE,
                                            MIGRATION_STATUS_FAILED);
         }

-- 
2.50.0

[PATCH v5 22/23] migration: Add error-parameterized function variants in VMSD struct

[Arun Menon]

- We need to have good error reporting in the callbacks in
  VMStateDescription struct. Specifically pre_save, post_save,
  pre_load and post_load callbacks.
- It is not possible to change these functions everywhere in one
  patch, therefore, we introduce a duplicate set of callbacks
  with Error object passed to them.
- So, in this commit, we implement 'errp' variants of these callbacks,
  introducing an explicit Error object parameter.
- This is a functional step towards transitioning the entire codebase
  to the new error-parameterized functions.
- Deliberately called in mutual exclusion from their counterparts,
  to prevent conflicts during the transition.
- New impls should preferentally use 'errp' variants of
  these methods, and existing impls incrementally converted.
  The variants without 'errp' are intended to be removed
  once all usage is converted.

Signed-off-by: Arun Menon <armenon@redhat.com>
---
 include/migration/vmstate.h | 11 +++++++++++
 migration/vmstate.c         | 36 +++++++++++++++++++++++++++++++-----
 2 files changed, 42 insertions(+), 5 deletions(-)

diff --git a/include/migration/vmstate.h b/include/migration/vmstate.h
index 056781b1c21e737583f081594d9f88b32adfd674..53fa72c1bbde399be02c88fc8745fdbb79bfd7c8 100644
--- a/include/migration/vmstate.h
+++ b/include/migration/vmstate.h
@@ -200,15 +200,26 @@ struct VMStateDescription {
      * exclusive. For this reason, also early_setup VMSDs are migrated in a
      * QEMU_VM_SECTION_FULL section, while save_setup() data is migrated in
      * a QEMU_VM_SECTION_START section.
+     *
+     * There are duplicate impls of the post/pre save/load hooks.
+     * New impls should preferentally use 'errp' variants of these
+     * methods and existing impls incrementally converted.
+     * The variants without 'errp' are intended to be removed
+     * once all usage is converted.
      */
+
     bool early_setup;
     int version_id;
     int minimum_version_id;
     MigrationPriority priority;
     int (*pre_load)(void *opaque);
+    int (*pre_load_errp)(void *opaque, Error **errp);
     int (*post_load)(void *opaque, int version_id);
+    int (*post_load_errp)(void *opaque, int version_id, Error **errp);
     int (*pre_save)(void *opaque);
+    int (*pre_save_errp)(void *opaque, Error **errp);
     int (*post_save)(void *opaque);
+    int (*post_save_errp)(void *opaque, Error **errp);
     bool (*needed)(void *opaque);
     bool (*dev_unplug_pending)(void *opaque);
 
diff --git a/migration/vmstate.c b/migration/vmstate.c
index 078a00003023cc248fb16f05017d4c4251fd86df..bff4539cbe526c5a0718678d4e1f32ba9ac57889 100644
--- a/migration/vmstate.c
+++ b/migration/vmstate.c
@@ -152,7 +152,13 @@ int vmstate_load_state(QEMUFile *f, const VMStateDescription *vmsd,
         trace_vmstate_load_state_end(vmsd->name, "too old", -EINVAL);
         return -EINVAL;
     }
-    if (vmsd->pre_load) {
+    if (vmsd->pre_load_errp) {
+        ret = vmsd->pre_load_errp(opaque, errp);
+        if (ret) {
+            error_prepend(errp, "VM pre load failed : %d ", ret);
+            return ret;
+        }
+    } else if (vmsd->pre_load) {
         ret = vmsd->pre_load(opaque);
         if (ret) {
             error_setg(errp, "VM pre load failed : %d", ret);
@@ -238,7 +244,12 @@ int vmstate_load_state(QEMUFile *f, const VMStateDescription *vmsd,
         qemu_file_set_error(f, ret);
         return ret;
     }
-    if (vmsd->post_load) {
+    if (vmsd->post_load_errp) {
+        ret = vmsd->post_load_errp(opaque, version_id, errp);
+        if (ret < 0) {
+            error_prepend(errp, "VM Post load failed : %d ", ret);
+        }
+    } else if (vmsd->post_load) {
         ret = vmsd->post_load(opaque, version_id);
         if (ret < 0) {
             error_setg(errp, "VM Post load failed : %d", ret);
@@ -414,7 +425,14 @@ int vmstate_save_state_v(QEMUFile *f, const VMStateDescription *vmsd,
 
     trace_vmstate_save_state_top(vmsd->name);
 
-    if (vmsd->pre_save) {
+    if (vmsd->pre_save_errp) {
+        ret = vmsd->pre_save_errp(opaque, errp);
+        trace_vmstate_save_state_pre_save_res(vmsd->name, ret);
+        if (ret) {
+            error_prepend(errp, "pre-save failed: %s ", vmsd->name);
+            return ret;
+        }
+    } else if (vmsd->pre_save) {
         ret = vmsd->pre_save(opaque);
         trace_vmstate_save_state_pre_save_res(vmsd->name, ret);
         if (ret) {
@@ -524,7 +542,9 @@ int vmstate_save_state_v(QEMUFile *f, const VMStateDescription *vmsd,
                 if (ret) {
                     error_setg(errp, "Save of field %s/%s failed",
                                 vmsd->name, field->name);
-                    if (vmsd->post_save) {
+                    if (vmsd->post_save_errp) {
+                        vmsd->post_save_errp(opaque, errp);
+                    } else if (vmsd->post_save) {
                         vmsd->post_save(opaque);
                     }
                     return ret;
@@ -552,7 +572,13 @@ int vmstate_save_state_v(QEMUFile *f, const VMStateDescription *vmsd,
 
     ret = vmstate_subsection_save(f, vmsd, opaque, vmdesc, errp);
 
-    if (vmsd->post_save) {
+    if (vmsd->post_save_errp) {
+        int ps_ret = vmsd->post_save_errp(opaque, errp);
+        if (!ret && ps_ret) {
+            ret = ps_ret;
+            error_prepend(errp, "post-save failed: %s ", vmsd->name);
+        }
+    } else if (vmsd->post_save) {
         int ps_ret = vmsd->post_save(opaque);
         if (!ret && ps_ret) {
             ret = ps_ret;

-- 
2.50.0

[PATCH v5 23/23] backends/tpm: Propagate vTPM error on migration failure

[Arun Menon]

- When migration of a VM with encrypted vTPM fails on the
  destination host, (e.g., due to a mismatch in secret values),
  the error message displayed on the source host is generic and unhelpful.
- For example, a typical error looks like this:
  "operation failed: job 'migration out' failed: Sibling indicated error 1.
  operation failed: job 'migration in' failed: load of migration failed:
  Input/output error"
- Such generic errors are logged using error_report(), which prints to
  the console/monitor but does not make the detailed error accessible via
  the QMP query-migrate command.
- This change, along with the set of changes of passing errp Error object
  to the VM state loading functions, help in addressing the issue.
  We use the post_load_errp hook of VMStateDescription to propagate errors
  by setting Error **errp objects in case of failure in the TPM backend.
- It can then be retrieved using QMP command:
  {"execute" : "query-migrate"}

Buglink: https://issues.redhat.com/browse/RHEL-82826

Reviewed-by: Stefan Berger <stefanb@linux.ibm.com>
Signed-off-by: Arun Menon <armenon@redhat.com>
---
 backends/tpm/tpm_emulator.c | 39 ++++++++++++++++++++-------------------
 1 file changed, 20 insertions(+), 19 deletions(-)

diff --git a/backends/tpm/tpm_emulator.c b/backends/tpm/tpm_emulator.c
index 4a234ab2c0b19b2604bf0dd8cb5f4540c72a9438..9bf5927e8e1542cf2e4f2275783d32853d5f1473 100644
--- a/backends/tpm/tpm_emulator.c
+++ b/backends/tpm/tpm_emulator.c
@@ -819,7 +819,8 @@ static int tpm_emulator_get_state_blobs(TPMEmulator *tpm_emu)
 static int tpm_emulator_set_state_blob(TPMEmulator *tpm_emu,
                                        uint32_t type,
                                        TPMSizedBuffer *tsb,
-                                       uint32_t flags)
+                                       uint32_t flags,
+                                       Error **errp)
 {
     ssize_t n;
     ptm_setstate pss;
@@ -838,17 +839,17 @@ static int tpm_emulator_set_state_blob(TPMEmulator *tpm_emu,
     /* write the header only */
     if (tpm_emulator_ctrlcmd(tpm_emu, CMD_SET_STATEBLOB, &pss,
                              offsetof(ptm_setstate, u.req.data), 0, 0) < 0) {
-        error_report("tpm-emulator: could not set state blob type %d : %s",
-                     type, strerror(errno));
+        error_setg(errp, "tpm-emulator: could not set state blob type %d : %s",
+                   type, strerror(errno));
         return -1;
     }
 
     /* now the body */
     n = qemu_chr_fe_write_all(&tpm_emu->ctrl_chr, tsb->buffer, tsb->size);
     if (n != tsb->size) {
-        error_report("tpm-emulator: Writing the stateblob (type %d) "
-                     "failed; could not write %u bytes, but only %zd",
-                     type, tsb->size, n);
+        error_setg(errp, "tpm-emulator: Writing the stateblob (type %d) "
+                   "failed; could not write %u bytes, but only %zd",
+                   type, tsb->size, n);
         return -1;
     }
 
@@ -856,17 +857,17 @@ static int tpm_emulator_set_state_blob(TPMEmulator *tpm_emu,
     n = qemu_chr_fe_read_all(&tpm_emu->ctrl_chr,
                              (uint8_t *)&pss, sizeof(pss.u.resp));
     if (n != sizeof(pss.u.resp)) {
-        error_report("tpm-emulator: Reading response from writing stateblob "
-                     "(type %d) failed; expected %zu bytes, got %zd", type,
-                     sizeof(pss.u.resp), n);
+        error_setg(errp, "tpm-emulator: Reading response from writing "
+                   "stateblob (type %d) failed; expected %zu bytes, "
+                   "got %zd", type, sizeof(pss.u.resp), n);
         return -1;
     }
 
     tpm_result = be32_to_cpu(pss.u.resp.tpm_result);
     if (tpm_result != 0) {
-        error_report("tpm-emulator: Setting the stateblob (type %d) failed "
-                     "with a TPM error 0x%x %s", type, tpm_result,
-                     tpm_emulator_strerror(tpm_result));
+        error_setg(errp, "tpm-emulator: Setting the stateblob (type %d) "
+                   "failed with a TPM error 0x%x %s", type, tpm_result,
+                   tpm_emulator_strerror(tpm_result));
         return -1;
     }
 
@@ -880,7 +881,7 @@ static int tpm_emulator_set_state_blob(TPMEmulator *tpm_emu,
  *
  * Returns a negative errno code in case of error.
  */
-static int tpm_emulator_set_state_blobs(TPMBackend *tb)
+static int tpm_emulator_set_state_blobs(TPMBackend *tb, Error **errp)
 {
     TPMEmulator *tpm_emu = TPM_EMULATOR(tb);
     TPMBlobBuffers *state_blobs = &tpm_emu->state_blobs;
@@ -894,13 +895,13 @@ static int tpm_emulator_set_state_blobs(TPMBackend *tb)
 
     if (tpm_emulator_set_state_blob(tpm_emu, PTM_BLOB_TYPE_PERMANENT,
                                     &state_blobs->permanent,
-                                    state_blobs->permanent_flags) < 0 ||
+                                    state_blobs->permanent_flags, errp) < 0 ||
         tpm_emulator_set_state_blob(tpm_emu, PTM_BLOB_TYPE_VOLATILE,
                                     &state_blobs->volatil,
-                                    state_blobs->volatil_flags) < 0 ||
+                                    state_blobs->volatil_flags, errp) < 0 ||
         tpm_emulator_set_state_blob(tpm_emu, PTM_BLOB_TYPE_SAVESTATE,
                                     &state_blobs->savestate,
-                                    state_blobs->savestate_flags) < 0) {
+                                    state_blobs->savestate_flags, errp) < 0) {
         return -EIO;
     }
 
@@ -948,12 +949,12 @@ static void tpm_emulator_vm_state_change(void *opaque, bool running,
  *
  * Returns negative errno codes in case of error.
  */
-static int tpm_emulator_post_load(void *opaque, int version_id)
+static int tpm_emulator_post_load(void *opaque, int version_id, Error **errp)
 {
     TPMBackend *tb = opaque;
     int ret;
 
-    ret = tpm_emulator_set_state_blobs(tb);
+    ret = tpm_emulator_set_state_blobs(tb, errp);
     if (ret < 0) {
         return ret;
     }
@@ -969,7 +970,7 @@ static const VMStateDescription vmstate_tpm_emulator = {
     .name = "tpm-emulator",
     .version_id = 0,
     .pre_save = tpm_emulator_pre_save,
-    .post_load = tpm_emulator_post_load,
+    .post_load_errp = tpm_emulator_post_load,
     .fields = (const VMStateField[]) {
         VMSTATE_UINT32(state_blobs.permanent_flags, TPMEmulator),
         VMSTATE_UINT32(state_blobs.permanent.size, TPMEmulator),

-- 
2.50.0

Re: [PATCH v5 16/23] migration: push Error **errp into loadvm_process_enable_colo()

[Akihiko Odaki]

On 2025/07/17 9:37, 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 loadvm_process_enable_colo() must report an error
> in errp, in case of failure.
> 
> Signed-off-by: Arun Menon <armenon@redhat.com>
> ---
>   include/migration/colo.h |  2 +-
>   migration/migration.c    | 12 ++++++------
>   migration/ram.c          |  8 ++++----
>   migration/ram.h          |  2 +-
>   migration/savevm.c       | 25 ++++++++++++-------------
>   5 files changed, 24 insertions(+), 25 deletions(-)
> 
> diff --git a/include/migration/colo.h b/include/migration/colo.h
> index 43222ef5ae6adc3f7d8aa6a48bef79af33d09208..d4fe422e4d335d3bef4f860f56400fcd73287a0e 100644
> --- a/include/migration/colo.h
> +++ b/include/migration/colo.h
> @@ -25,7 +25,7 @@ void migrate_start_colo_process(MigrationState *s);
>   bool migration_in_colo_state(void);
>   
>   /* loadvm */
> -int migration_incoming_enable_colo(void);
> +int migration_incoming_enable_colo(Error **errp);
>   void migration_incoming_disable_colo(void);
>   bool migration_incoming_colo_enabled(void);
>   bool migration_incoming_in_colo_state(void);
> diff --git a/migration/migration.c b/migration/migration.c
> index 10c216d25dec01f206eacad2edd24d21f00e614c..326487882c8d41e2f89f99f69df0d9d4d42705e4 100644
> --- a/migration/migration.c
> +++ b/migration/migration.c
> @@ -623,22 +623,22 @@ void migration_incoming_disable_colo(void)
>       migration_colo_enabled = false;
>   }
>   
> -int migration_incoming_enable_colo(void)
> +int migration_incoming_enable_colo(Error **errp)
>   {
>   #ifndef CONFIG_REPLICATION
> -    error_report("ENABLE_COLO command come in migration stream, but the "
> -                 "replication module is not built in");
> +    error_setg(errp, "ENABLE_COLO command come in migration stream, but the "
> +               "replication module is not built in");
>       return -ENOTSUP;
>   #endif
>   
>       if (!migrate_colo()) {
> -        error_report("ENABLE_COLO command come in migration stream, but x-colo "
> -                     "capability is not set");
> +        error_setg(errp, "ENABLE_COLO command come in migration stream"
> +                   ", but x-colo capability is not set");
>           return -EINVAL;
>       }
>   
>       if (ram_block_discard_disable(true)) {
> -        error_report("COLO: cannot disable RAM discard");
> +        error_setg(errp, "COLO: cannot disable RAM discard");
>           return -EBUSY;
>       }
>       migration_colo_enabled = true;
> diff --git a/migration/ram.c b/migration/ram.c
> index 8223183132dc0f558f45fbae3f4f832845730bd3..607c979cc15a3d321e5e3e380ac7613d80d86fc9 100644
> --- a/migration/ram.c
> +++ b/migration/ram.c
> @@ -3576,7 +3576,7 @@ static void colo_init_ram_state(void)
>    * memory of the secondary VM, it is need to hold the global lock
>    * to call this helper.
>    */
> -int colo_init_ram_cache(void)
> +int colo_init_ram_cache(Error **errp)
>   {
>       RAMBlock *block;
>   
> @@ -3585,9 +3585,9 @@ int colo_init_ram_cache(void)
>               block->colo_cache = qemu_anon_ram_alloc(block->used_length,
>                                                       NULL, false, false);
>               if (!block->colo_cache) {
> -                error_report("%s: Can't alloc memory for COLO cache of block %s,"
> -                             "size 0x" RAM_ADDR_FMT, __func__, block->idstr,
> -                             block->used_length);
> +                error_setg(errp, "%s: Can't alloc memory for COLO cache of "
> +                           "block %s, size 0x" RAM_ADDR_FMT, __func__,
> +                           block->idstr, block->used_length);
>                   RAMBLOCK_FOREACH_NOT_IGNORED(block) {
>                       if (block->colo_cache) {
>                           qemu_anon_ram_free(block->colo_cache, block->used_length);
> diff --git a/migration/ram.h b/migration/ram.h
> index 275709a99187f9429ccb4111e05281ec268ba0db..24cd0bf585762cfa1e86834dc03c6baeea2f0627 100644
> --- a/migration/ram.h
> +++ b/migration/ram.h
> @@ -109,7 +109,7 @@ void ramblock_set_file_bmap_atomic(RAMBlock *block, ram_addr_t offset,
>                                      bool set);
>   
>   /* ram cache */
> -int colo_init_ram_cache(void);
> +int colo_init_ram_cache(Error **errp);
>   void colo_flush_ram_cache(void);
>   void colo_release_ram_cache(void);
>   void colo_incoming_start_dirty_log(void);
> diff --git a/migration/savevm.c b/migration/savevm.c
> index 1cbc44a5314043a403d983511066cf137681a18d..755ba7e4504d377a4649da191ad9875d9fd66f69 100644
> --- a/migration/savevm.c
> +++ b/migration/savevm.c
> @@ -2510,15 +2510,19 @@ static int loadvm_handle_recv_bitmap(MigrationIncomingState *mis,
>       return 0;
>   }
>   
> -static int loadvm_process_enable_colo(MigrationIncomingState *mis)
> +static int loadvm_process_enable_colo(MigrationIncomingState *mis,
> +                                      Error **errp)
>   {
> -    int ret = migration_incoming_enable_colo();
> +    int ret;
>   
> -    if (!ret) {
> -        ret = colo_init_ram_cache();
> -        if (ret) {
> -            migration_incoming_disable_colo();
> -        }
> +    if (migration_incoming_enable_colo(errp) < 0) {
> +        return -1;

Returning -1 here while colo_init_ram_cache() returns -errno results in 
an inconsistent semantics of this function's return value.

Ideally, I think this function (and other similar functions) should stop 
returning -errno and instead return a bool value to prevent callers to 
make any assumption based on the return value other than 
success/failure. But that could be done later; let it return -errno 
until then.

Re: [PATCH v5 09/23] migration: push Error **errp into ram_postcopy_incoming_init()

[Akihiko Odaki]

On 2025/07/17 9:37, 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 ram_postcopy_incoming_init() must report an error
> in errp, in case of failure.
> 
> Signed-off-by: Arun Menon <armenon@redhat.com>
> ---
>   migration/postcopy-ram.c | 9 ++++++---
>   migration/postcopy-ram.h | 2 +-
>   migration/ram.c          | 6 +++---
>   migration/ram.h          | 2 +-
>   migration/savevm.c       | 2 +-
>   5 files changed, 12 insertions(+), 9 deletions(-)
> 
> diff --git a/migration/postcopy-ram.c b/migration/postcopy-ram.c
> index 45af9a361e8eacaad0fb217a5da2c5004416c1da..05617e5fbcad62226a54fe17d9f7d9a316baf1e4 100644
> --- a/migration/postcopy-ram.c
> +++ b/migration/postcopy-ram.c
> @@ -681,6 +681,7 @@ out:
>    */
>   static int init_range(RAMBlock *rb, void *opaque)
>   {
> +    Error **errp = opaque;
>       const char *block_name = qemu_ram_get_idstr(rb);
>       void *host_addr = qemu_ram_get_host_addr(rb);
>       ram_addr_t offset = qemu_ram_get_offset(rb);
> @@ -701,6 +702,8 @@ static int init_range(RAMBlock *rb, void *opaque)
>        * (Precopy will just overwrite this data, so doesn't need the discard)
>        */
>       if (ram_discard_range(block_name, 0, length)) {
> +        error_setg(errp, "failed to discard RAM block %s len=%zu",
> +                   block_name, length);
>           return -1;
>       }
>   
> @@ -749,9 +752,9 @@ static int cleanup_range(RAMBlock *rb, void *opaque)
>    * postcopy later; must be called prior to any precopy.
>    * called from arch_init's similarly named ram_postcopy_incoming_init
>    */
> -int postcopy_ram_incoming_init(MigrationIncomingState *mis)
> +int postcopy_ram_incoming_init(MigrationIncomingState *mis, Error **errp)
>   {
> -    if (foreach_not_ignored_block(init_range, NULL)) {
> +    if (foreach_not_ignored_block(init_range, errp)) {
>           return -1;
>       }
>   
> @@ -1703,7 +1706,7 @@ bool postcopy_ram_supported_by_host(MigrationIncomingState *mis, Error **errp)
>       return false;
>   }
>   
> -int postcopy_ram_incoming_init(MigrationIncomingState *mis)
> +int postcopy_ram_incoming_init(MigrationIncomingState *mis, Error **errp)
>   {
>       error_report("postcopy_ram_incoming_init: No OS support");
>       return -1;
> diff --git a/migration/postcopy-ram.h b/migration/postcopy-ram.h
> index 3852141d7e37ab18bada4b46c137fef0969d0070..ca19433b246893fa5105bcebffb442c58a9a4f48 100644
> --- a/migration/postcopy-ram.h
> +++ b/migration/postcopy-ram.h
> @@ -30,7 +30,7 @@ int postcopy_ram_incoming_setup(MigrationIncomingState *mis);
>    * postcopy later; must be called prior to any precopy.
>    * called from ram.c's similarly named ram_postcopy_incoming_init
>    */
> -int postcopy_ram_incoming_init(MigrationIncomingState *mis);
> +int postcopy_ram_incoming_init(MigrationIncomingState *mis, Error **errp);
>   
>   /*
>    * At the end of a migration where postcopy_ram_incoming_init was called.
> diff --git a/migration/ram.c b/migration/ram.c
> index 7208bc114fb5c366740db380ee6956a91b3871a0..8223183132dc0f558f45fbae3f4f832845730bd3 100644
> --- a/migration/ram.c
> +++ b/migration/ram.c
> @@ -3708,7 +3708,7 @@ static int ram_load_cleanup(void *opaque)
>   /**
>    * ram_postcopy_incoming_init: allocate postcopy data structures
>    *
> - * Returns 0 for success and negative if there was one error
> + * Returns 0 for success and -1 if there was one error

This is true but not relevant in this patch's goal.

Besides, I'm not in favor of letting callers make an assumption on 
integer return values (i.e., let callers assume a particular integer 
value in the error conditions). It is subtle to make a mistake to return 
-errno while the documentation says it returns -1.

I think a proper way to avoid bugs due to return values here is to 
change the type to bool, which ensures there are two possible values; 
that is a nice improvement but something that can be done later.

>    *
>    * @mis: current migration incoming state
>    *
> @@ -3716,9 +3716,9 @@ static int ram_load_cleanup(void *opaque)
>    * postcopy-ram. postcopy-ram's similarly names
>    * postcopy_ram_incoming_init does the work.
>    */
> -int ram_postcopy_incoming_init(MigrationIncomingState *mis)
> +int ram_postcopy_incoming_init(MigrationIncomingState *mis, Error **errp)
>   {
> -    return postcopy_ram_incoming_init(mis);
> +    return postcopy_ram_incoming_init(mis, errp);
>   }
>   
>   /**
> diff --git a/migration/ram.h b/migration/ram.h
> index 921c39a2c5c45bc2344be80854c46e4c10c09aeb..275709a99187f9429ccb4111e05281ec268ba0db 100644
> --- a/migration/ram.h
> +++ b/migration/ram.h
> @@ -86,7 +86,7 @@ void ram_postcopy_migrated_memory_release(MigrationState *ms);
>   void ram_postcopy_send_discard_bitmap(MigrationState *ms);
>   /* For incoming postcopy discard */
>   int ram_discard_range(const char *block_name, uint64_t start, size_t length);
> -int ram_postcopy_incoming_init(MigrationIncomingState *mis);
> +int ram_postcopy_incoming_init(MigrationIncomingState *mis, Error **errp);
>   int ram_load_postcopy(QEMUFile *f, int channel);
>   
>   void ram_handle_zero(void *host, uint64_t size);
> diff --git a/migration/savevm.c b/migration/savevm.c
> index d1edeaac5f2a5df2f6d94357388be807a938b2ef..8eba151a693b7f2dc58853292c92024288eae81e 100644
> --- a/migration/savevm.c
> +++ b/migration/savevm.c
> @@ -1983,7 +1983,7 @@ static int loadvm_postcopy_handle_advise(MigrationIncomingState *mis,
>           return -1;
>       }
>   
> -    if (ram_postcopy_incoming_init(mis)) {
> +    if (ram_postcopy_incoming_init(mis, NULL)) {
>           return -1;
>       }
>   
> 

Re: [PATCH v5 09/23] migration: push Error **errp into ram_postcopy_incoming_init()

[Arun Menon]

Hi Akihiko,

Thanks for the review.

On Thu, Jul 17, 2025 at 12:34:21PM +0900, Akihiko Odaki wrote:
> On 2025/07/17 9:37, 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 ram_postcopy_incoming_init() must report an error
> > in errp, in case of failure.
> > 
> > Signed-off-by: Arun Menon <armenon@redhat.com>
> > ---
> >   migration/postcopy-ram.c | 9 ++++++---
> >   migration/postcopy-ram.h | 2 +-
> >   migration/ram.c          | 6 +++---
> >   migration/ram.h          | 2 +-
> >   migration/savevm.c       | 2 +-
> >   5 files changed, 12 insertions(+), 9 deletions(-)
> > 
> > diff --git a/migration/postcopy-ram.c b/migration/postcopy-ram.c
> > index 45af9a361e8eacaad0fb217a5da2c5004416c1da..05617e5fbcad62226a54fe17d9f7d9a316baf1e4 100644
> > --- a/migration/postcopy-ram.c
> > +++ b/migration/postcopy-ram.c
> > @@ -681,6 +681,7 @@ out:
> >    */
> >   static int init_range(RAMBlock *rb, void *opaque)
> >   {
> > +    Error **errp = opaque;
> >       const char *block_name = qemu_ram_get_idstr(rb);
> >       void *host_addr = qemu_ram_get_host_addr(rb);
> >       ram_addr_t offset = qemu_ram_get_offset(rb);
> > @@ -701,6 +702,8 @@ static int init_range(RAMBlock *rb, void *opaque)
> >        * (Precopy will just overwrite this data, so doesn't need the discard)
> >        */
> >       if (ram_discard_range(block_name, 0, length)) {
> > +        error_setg(errp, "failed to discard RAM block %s len=%zu",
> > +                   block_name, length);
> >           return -1;
> >       }
> > @@ -749,9 +752,9 @@ static int cleanup_range(RAMBlock *rb, void *opaque)
> >    * postcopy later; must be called prior to any precopy.
> >    * called from arch_init's similarly named ram_postcopy_incoming_init
> >    */
> > -int postcopy_ram_incoming_init(MigrationIncomingState *mis)
> > +int postcopy_ram_incoming_init(MigrationIncomingState *mis, Error **errp)
> >   {
> > -    if (foreach_not_ignored_block(init_range, NULL)) {
> > +    if (foreach_not_ignored_block(init_range, errp)) {
> >           return -1;
> >       }
> > @@ -1703,7 +1706,7 @@ bool postcopy_ram_supported_by_host(MigrationIncomingState *mis, Error **errp)
> >       return false;
> >   }
> > -int postcopy_ram_incoming_init(MigrationIncomingState *mis)
> > +int postcopy_ram_incoming_init(MigrationIncomingState *mis, Error **errp)
> >   {
> >       error_report("postcopy_ram_incoming_init: No OS support");
> >       return -1;
> > diff --git a/migration/postcopy-ram.h b/migration/postcopy-ram.h
> > index 3852141d7e37ab18bada4b46c137fef0969d0070..ca19433b246893fa5105bcebffb442c58a9a4f48 100644
> > --- a/migration/postcopy-ram.h
> > +++ b/migration/postcopy-ram.h
> > @@ -30,7 +30,7 @@ int postcopy_ram_incoming_setup(MigrationIncomingState *mis);
> >    * postcopy later; must be called prior to any precopy.
> >    * called from ram.c's similarly named ram_postcopy_incoming_init
> >    */
> > -int postcopy_ram_incoming_init(MigrationIncomingState *mis);
> > +int postcopy_ram_incoming_init(MigrationIncomingState *mis, Error **errp);
> >   /*
> >    * At the end of a migration where postcopy_ram_incoming_init was called.
> > diff --git a/migration/ram.c b/migration/ram.c
> > index 7208bc114fb5c366740db380ee6956a91b3871a0..8223183132dc0f558f45fbae3f4f832845730bd3 100644
> > --- a/migration/ram.c
> > +++ b/migration/ram.c
> > @@ -3708,7 +3708,7 @@ static int ram_load_cleanup(void *opaque)
> >   /**
> >    * ram_postcopy_incoming_init: allocate postcopy data structures
> >    *
> > - * Returns 0 for success and negative if there was one error
> > + * Returns 0 for success and -1 if there was one error
> 
> This is true but not relevant in this patch's goal.
> 
> Besides, I'm not in favor of letting callers make an assumption on integer
> return values (i.e., let callers assume a particular integer value in the
> error conditions). It is subtle to make a mistake to return -errno while the
> documentation says it returns -1.
> 
> I think a proper way to avoid bugs due to return values here is to change
> the type to bool, which ensures there are two possible values; that is a
> nice improvement but something that can be done later.

I agree, I shall remove the unnecessary documentation change as it is not in
the scope.

> 
> >    *
> >    * @mis: current migration incoming state
> >    *
> > @@ -3716,9 +3716,9 @@ static int ram_load_cleanup(void *opaque)
> >    * postcopy-ram. postcopy-ram's similarly names
> >    * postcopy_ram_incoming_init does the work.
> >    */
> > -int ram_postcopy_incoming_init(MigrationIncomingState *mis)
> > +int ram_postcopy_incoming_init(MigrationIncomingState *mis, Error **errp)
> >   {
> > -    return postcopy_ram_incoming_init(mis);
> > +    return postcopy_ram_incoming_init(mis, errp);
> >   }
> >   /**
> > diff --git a/migration/ram.h b/migration/ram.h
> > index 921c39a2c5c45bc2344be80854c46e4c10c09aeb..275709a99187f9429ccb4111e05281ec268ba0db 100644
> > --- a/migration/ram.h
> > +++ b/migration/ram.h
> > @@ -86,7 +86,7 @@ void ram_postcopy_migrated_memory_release(MigrationState *ms);
> >   void ram_postcopy_send_discard_bitmap(MigrationState *ms);
> >   /* For incoming postcopy discard */
> >   int ram_discard_range(const char *block_name, uint64_t start, size_t length);
> > -int ram_postcopy_incoming_init(MigrationIncomingState *mis);
> > +int ram_postcopy_incoming_init(MigrationIncomingState *mis, Error **errp);
> >   int ram_load_postcopy(QEMUFile *f, int channel);
> >   void ram_handle_zero(void *host, uint64_t size);
> > diff --git a/migration/savevm.c b/migration/savevm.c
> > index d1edeaac5f2a5df2f6d94357388be807a938b2ef..8eba151a693b7f2dc58853292c92024288eae81e 100644
> > --- a/migration/savevm.c
> > +++ b/migration/savevm.c
> > @@ -1983,7 +1983,7 @@ static int loadvm_postcopy_handle_advise(MigrationIncomingState *mis,
> >           return -1;
> >       }
> > -    if (ram_postcopy_incoming_init(mis)) {
> > +    if (ram_postcopy_incoming_init(mis, NULL)) {
> >           return -1;
> >       }
> > 
> 

Regards,
Arun

Re: [PATCH v5 16/23] migration: push Error **errp into loadvm_process_enable_colo()

[Arun Menon]

On Thu, Jul 17, 2025 at 12:26:16PM +0900, Akihiko Odaki wrote:
> On 2025/07/17 9:37, 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 loadvm_process_enable_colo() must report an error
> > in errp, in case of failure.
> > 
> > Signed-off-by: Arun Menon <armenon@redhat.com>
> > ---
> >   include/migration/colo.h |  2 +-
> >   migration/migration.c    | 12 ++++++------
> >   migration/ram.c          |  8 ++++----
> >   migration/ram.h          |  2 +-
> >   migration/savevm.c       | 25 ++++++++++++-------------
> >   5 files changed, 24 insertions(+), 25 deletions(-)
> > 
> > diff --git a/include/migration/colo.h b/include/migration/colo.h
> > index 43222ef5ae6adc3f7d8aa6a48bef79af33d09208..d4fe422e4d335d3bef4f860f56400fcd73287a0e 100644
> > --- a/include/migration/colo.h
> > +++ b/include/migration/colo.h
> > @@ -25,7 +25,7 @@ void migrate_start_colo_process(MigrationState *s);
> >   bool migration_in_colo_state(void);
> >   /* loadvm */
> > -int migration_incoming_enable_colo(void);
> > +int migration_incoming_enable_colo(Error **errp);
> >   void migration_incoming_disable_colo(void);
> >   bool migration_incoming_colo_enabled(void);
> >   bool migration_incoming_in_colo_state(void);
> > diff --git a/migration/migration.c b/migration/migration.c
> > index 10c216d25dec01f206eacad2edd24d21f00e614c..326487882c8d41e2f89f99f69df0d9d4d42705e4 100644
> > --- a/migration/migration.c
> > +++ b/migration/migration.c
> > @@ -623,22 +623,22 @@ void migration_incoming_disable_colo(void)
> >       migration_colo_enabled = false;
> >   }
> > -int migration_incoming_enable_colo(void)
> > +int migration_incoming_enable_colo(Error **errp)
> >   {
> >   #ifndef CONFIG_REPLICATION
> > -    error_report("ENABLE_COLO command come in migration stream, but the "
> > -                 "replication module is not built in");
> > +    error_setg(errp, "ENABLE_COLO command come in migration stream, but the "
> > +               "replication module is not built in");
> >       return -ENOTSUP;
> >   #endif
> >       if (!migrate_colo()) {
> > -        error_report("ENABLE_COLO command come in migration stream, but x-colo "
> > -                     "capability is not set");
> > +        error_setg(errp, "ENABLE_COLO command come in migration stream"
> > +                   ", but x-colo capability is not set");
> >           return -EINVAL;
> >       }
> >       if (ram_block_discard_disable(true)) {
> > -        error_report("COLO: cannot disable RAM discard");
> > +        error_setg(errp, "COLO: cannot disable RAM discard");
> >           return -EBUSY;
> >       }
> >       migration_colo_enabled = true;
> > diff --git a/migration/ram.c b/migration/ram.c
> > index 8223183132dc0f558f45fbae3f4f832845730bd3..607c979cc15a3d321e5e3e380ac7613d80d86fc9 100644
> > --- a/migration/ram.c
> > +++ b/migration/ram.c
> > @@ -3576,7 +3576,7 @@ static void colo_init_ram_state(void)
> >    * memory of the secondary VM, it is need to hold the global lock
> >    * to call this helper.
> >    */
> > -int colo_init_ram_cache(void)
> > +int colo_init_ram_cache(Error **errp)
> >   {
> >       RAMBlock *block;
> > @@ -3585,9 +3585,9 @@ int colo_init_ram_cache(void)
> >               block->colo_cache = qemu_anon_ram_alloc(block->used_length,
> >                                                       NULL, false, false);
> >               if (!block->colo_cache) {
> > -                error_report("%s: Can't alloc memory for COLO cache of block %s,"
> > -                             "size 0x" RAM_ADDR_FMT, __func__, block->idstr,
> > -                             block->used_length);
> > +                error_setg(errp, "%s: Can't alloc memory for COLO cache of "
> > +                           "block %s, size 0x" RAM_ADDR_FMT, __func__,
> > +                           block->idstr, block->used_length);
> >                   RAMBLOCK_FOREACH_NOT_IGNORED(block) {
> >                       if (block->colo_cache) {
> >                           qemu_anon_ram_free(block->colo_cache, block->used_length);
> > diff --git a/migration/ram.h b/migration/ram.h
> > index 275709a99187f9429ccb4111e05281ec268ba0db..24cd0bf585762cfa1e86834dc03c6baeea2f0627 100644
> > --- a/migration/ram.h
> > +++ b/migration/ram.h
> > @@ -109,7 +109,7 @@ void ramblock_set_file_bmap_atomic(RAMBlock *block, ram_addr_t offset,
> >                                      bool set);
> >   /* ram cache */
> > -int colo_init_ram_cache(void);
> > +int colo_init_ram_cache(Error **errp);
> >   void colo_flush_ram_cache(void);
> >   void colo_release_ram_cache(void);
> >   void colo_incoming_start_dirty_log(void);
> > diff --git a/migration/savevm.c b/migration/savevm.c
> > index 1cbc44a5314043a403d983511066cf137681a18d..755ba7e4504d377a4649da191ad9875d9fd66f69 100644
> > --- a/migration/savevm.c
> > +++ b/migration/savevm.c
> > @@ -2510,15 +2510,19 @@ static int loadvm_handle_recv_bitmap(MigrationIncomingState *mis,
> >       return 0;
> >   }
> > -static int loadvm_process_enable_colo(MigrationIncomingState *mis)
> > +static int loadvm_process_enable_colo(MigrationIncomingState *mis,
> > +                                      Error **errp)
> >   {
> > -    int ret = migration_incoming_enable_colo();
> > +    int ret;
> > -    if (!ret) {
> > -        ret = colo_init_ram_cache();
> > -        if (ret) {
> > -            migration_incoming_disable_colo();
> > -        }
> > +    if (migration_incoming_enable_colo(errp) < 0) {
> > +        return -1;
> 
> Returning -1 here while colo_init_ram_cache() returns -errno results in an
> inconsistent semantics of this function's return value.

If I understand correctly, you mean, if migration_incoming_enable_colo() fails, it should 
return the errno instead of -1. Will do.
Thanks

> 
> Ideally, I think this function (and other similar functions) should stop
> returning -errno and instead return a bool value to prevent callers to make
> any assumption based on the return value other than success/failure. But
> that could be done later; let it return -errno until then.
> 
yes

Re: [PATCH v5 01/23] migration: push Error **errp into vmstate_subsection_load()

[Daniel P. Berrangé]

On Thu, Jul 17, 2025 at 06:07:24AM +0530, 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_subsection_load() must report an error
> in errp, in case of failure.
> 
> Signed-off-by: Arun Menon <armenon@redhat.com>
> ---
>  migration/vmstate.c | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
> 
> diff --git a/migration/vmstate.c b/migration/vmstate.c
> index 5feaa3244d259874f03048326b2497e7db32e47c..526668a020562f303d2ddf030b1c8466659b67be 100644
> --- a/migration/vmstate.c
> +++ b/migration/vmstate.c
> @@ -25,7 +25,7 @@ static int vmstate_subsection_save(QEMUFile *f, const VMStateDescription *vmsd,
>                                     void *opaque, JSONWriter *vmdesc,
>                                     Error **errp);
>  static int vmstate_subsection_load(QEMUFile *f, const VMStateDescription *vmsd,
> -                                   void *opaque);
> +                                   void *opaque, Error **errp);
>  
>  /* Whether this field should exist for either save or load the VM? */
>  static bool
> @@ -225,7 +225,7 @@ int vmstate_load_state(QEMUFile *f, const VMStateDescription *vmsd,
>          field++;
>      }
>      assert(field->flags == VMS_END);
> -    ret = vmstate_subsection_load(f, vmsd, opaque);
> +    ret = vmstate_subsection_load(f, vmsd, opaque, NULL);
>      if (ret != 0) {
>          qemu_file_set_error(f, ret);
>          return ret;
> @@ -566,7 +566,7 @@ vmstate_get_subsection(const VMStateDescription * const *sub,
>  }
>  
>  static int vmstate_subsection_load(QEMUFile *f, const VMStateDescription *vmsd,
> -                                   void *opaque)
> +                                   void *opaque, Error **errp)
>  {
>      trace_vmstate_subsection_load(vmsd->name);
>  
> @@ -598,6 +598,7 @@ static int vmstate_subsection_load(QEMUFile *f, const VMStateDescription *vmsd,
>          sub_vmsd = vmstate_get_subsection(vmsd->subsections, idstr);
>          if (sub_vmsd == NULL) {
>              trace_vmstate_subsection_load_bad(vmsd->name, idstr, "(lookup)");
> +            error_setg(errp, "VM subsection does not exist");

Lets include the contextual details

           error_setg(errp, "VM subsection '%s' in '%s' does not exist", idstr, vmsd->name);

>              return -ENOENT;
>          }
>          qemu_file_skip(f, 1); /* subsection */
> @@ -608,6 +609,7 @@ static int vmstate_subsection_load(QEMUFile *f, const VMStateDescription *vmsd,
>          ret = vmstate_load_state(f, sub_vmsd, opaque, version_id);
>          if (ret) {
>              trace_vmstate_subsection_load_bad(vmsd->name, idstr, "(child)");
> +            error_setg(errp, "Loading VM subsection failed : %d", ret);

           error_setg(errp, "Loading VM subsection '%s' in '%s' failed : %d", idstr, vmsd->name, ret);

>              return ret;
>          }
>      }

In general this method puzzles me. There are four places where we call
trace_vmstate_subsection_load_bad() whose name indicates it is for an
error condition.

The first two places, however, then 'return 0' to the caller indicating
success, which looks inconsistent with the trace point. Assuming that
is correct though, then your patch is also correct in only adding error
reports to these two places.



With regards,
Daniel
-- 
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Re: [PATCH v5 02/23] migration: push Error **errp into vmstate_load_state()

[Daniel P. Berrangé]

On Thu, Jul 17, 2025 at 06:07:25AM +0530, 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 <armenon@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         | 43 +++++++++++++++++++++++++++----------------
>  tests/unit/test-vmstate.c   | 18 +++++++++---------
>  ui/vdagent.c                |  2 +-
>  15 files changed, 58 insertions(+), 45 deletions(-)
> 

> diff --git a/migration/vmstate.c b/migration/vmstate.c
> index 526668a020562f303d2ddf030b1c8466659b67be..078a00003023cc248fb16f05017d4c4251fd86df 100644
> --- a/migration/vmstate.c
> +++ b/migration/vmstate.c
> @@ -132,29 +132,30 @@ 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 : %d", ret);

Suggest including

  vmsd->name, version_id, vmsd->minimum_version_id

as those are all relevant context which may aid in diagnosing
this error.

>              return ret;
>          }
>      }
> @@ -192,10 +193,12 @@ 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);

This should have the "error_setg" call, so...

> @@ -211,27 +214,35 @@ 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);
> +                    if (errp != NULL) {
> +                        error_prepend(errp, "Failed to load %s:%s ", vmsd->name,
> +                                      field->name);
> +                    } else {
> +                        error_setg(errp, "Failed to load %s:%s", vmsd->name,
> +                                   field->name);
> +                    }

...this should exclusively do error_prepend.

Also include the 'version_id' here as an bit of extra context.

>                      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",
> +                       vmsd->name, field->name);


Inlucde the version_id too

>              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 : %d", ret);
> +        }

Suggest including

  vmsd->name, version_id, vmsd->minimum_version_id


>      }
>      trace_vmstate_load_state_end(vmsd->name, "end", ret);
>      return ret;



With regards,
Daniel
-- 
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Re: [PATCH v5 03/23] migration: push Error **errp into qemu_loadvm_state_header()

[Daniel P. Berrangé]

On Thu, Jul 17, 2025 at 06:07:26AM +0530, 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 qemu_loadvm_state_header() must report an error
> in errp, in case of failure.
> 
> Signed-off-by: Arun Menon <armenon@redhat.com>
> ---
>  migration/savevm.c | 25 ++++++++++++++++---------
>  1 file changed, 16 insertions(+), 9 deletions(-)
> 
> diff --git a/migration/savevm.c b/migration/savevm.c
> index ab947620f724874f325fb9fb59bef50b7c16fb51..3ccbc724eb808db09b77088a858ecc7f06b21155 100644
> --- a/migration/savevm.c
> +++ b/migration/savevm.c
> @@ -2814,35 +2814,42 @@ qemu_loadvm_section_part_end(QEMUFile *f, uint8_t type)
>      return 0;
>  }
>  
> -static int qemu_loadvm_state_header(QEMUFile *f)
> +static int qemu_loadvm_state_header(QEMUFile *f, Error **errp)
>  {
>      unsigned int v;
>      int ret;
>  
>      v = qemu_get_be32(f);
>      if (v != QEMU_VM_FILE_MAGIC) {
> -        error_report("Not a migration stream");
> +        error_setg(errp, "Not a migration stream, "
> +                   "magic: %x != %x", v, QEMU_VM_FILE_MAGIC);
>          return -EINVAL;
>      }
>  
>      v = qemu_get_be32(f);
>      if (v == QEMU_VM_FILE_VERSION_COMPAT) {
> -        error_report("SaveVM v2 format is obsolete and don't work anymore");
> +        error_setg(errp, "SaveVM v2 format is obsolete and don't "
> +                   "work anymore, file version %x != %x",

This is a pre-existing issue, but can be fix the tail end of the
message to say

   "SaveVM v2 format is obsolete and no longer supported, file version %x != %x"



With regards,
Daniel
-- 
|: https://berrange.com      -o-    https://www.flickr.com/photos/dberrange :|
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Re: [PATCH v5 04/23] migration: push Error **errp into vmstate_load()

[Daniel P. Berrangé]

On Thu, Jul 17, 2025 at 06:07:27AM +0530, 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() must report an error
> in errp, in case of failure.
> 
> Signed-off-by: Arun Menon <armenon@redhat.com>
> ---
>  migration/savevm.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/migration/savevm.c b/migration/savevm.c
> index 3ccbc724eb808db09b77088a858ecc7f06b21155..1c1a46e4a01f812b559c451d278916426aa1cf40 100644
> --- a/migration/savevm.c
> +++ b/migration/savevm.c
> @@ -963,14 +963,14 @@ void vmstate_unregister(VMStateIf *obj, const VMStateDescription *vmsd,
>      }
>  }
>  
> -static int vmstate_load(QEMUFile *f, SaveStateEntry *se)
> +static int vmstate_load(QEMUFile *f, SaveStateEntry *se, Error **errp)
>  {
>      trace_vmstate_load(se->idstr, se->vmsd ? se->vmsd->name : "(old)");
>      if (!se->vmsd) {         /* Old style */
>          return se->ops->load_state(f, se->opaque, se->load_version_id);

This method can return a failure code, so we need error_setg() here
surely ? (and later augment/replace 'load_state' with a variant that
has an "errp" parameter)

>      }
>      return vmstate_load_state(f, se->vmsd, se->opaque, se->load_version_id,
> -                              NULL);
> +                              errp);
>  }
>  

With regards,
Daniel
-- 
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Re: [PATCH v5 05/23] migration: push Error **errp into qemu_loadvm_section_start_full()

[Daniel P. Berrangé]

On Thu, Jul 17, 2025 at 06:07:28AM +0530, 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 qemu_loadvm_section_start_full() must report an error
> in errp, in case of failure.
> 
> Signed-off-by: Arun Menon <armenon@redhat.com>
> ---
>  migration/savevm.c | 34 ++++++++++++++++++----------------
>  1 file changed, 18 insertions(+), 16 deletions(-)
> 
> diff --git a/migration/savevm.c b/migration/savevm.c
> index 1c1a46e4a01f812b559c451d278916426aa1cf40..63125971751394b72efc9bcaf7c4364715eef07f 100644
> --- a/migration/savevm.c
> +++ b/migration/savevm.c
> @@ -2684,7 +2684,7 @@ static bool check_section_footer(QEMUFile *f, SaveStateEntry *se)

> @@ -2705,8 +2705,8 @@ qemu_loadvm_section_start_full(QEMUFile *f, uint8_t type)
>  
>      ret = qemu_file_get_error(f);
>      if (ret) {
> -        error_report("%s: Failed to read instance/version ID: %d",
> -                     __func__, ret);
> +        error_setg(errp, "%s: Failed to read instance/version ID: %d",
> +                   __func__, ret);

If we're going to use "__func__" in error messages, it should be done
universally, not as a one-off. IMHO, it is almost always not desirable
though, as error messages ought to be expressive enough to not need
the C function name included.  IOW, just drop __func__, it is fine
without it here.

> @@ -2755,6 +2756,7 @@ qemu_loadvm_section_start_full(QEMUFile *f, uint8_t type)
>      }
>  
>      if (!check_section_footer(f, se)) {
> +        error_setg(errp, "Reading footer section failed");

Since we have them from earlier, can you include things like
idstr, instance_id, version_id as context.


With regards,
Daniel
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Re: [PATCH v5 06/23] migration: push Error **errp into qemu_loadvm_section_part_end()

[Daniel P. Berrangé]

On Thu, Jul 17, 2025 at 06:07:29AM +0530, 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 qemu_loadvm_section_part_end() must report an error
> in errp, in case of failure.
> 
> Signed-off-by: Arun Menon <armenon@redhat.com>
> ---
>  migration/savevm.c | 17 +++++++++--------
>  1 file changed, 9 insertions(+), 8 deletions(-)
> 
> diff --git a/migration/savevm.c b/migration/savevm.c
> index 63125971751394b72efc9bcaf7c4364715eef07f..22d73999595384519c755c9416b74ba1263a8bb9 100644
> --- a/migration/savevm.c
> +++ b/migration/savevm.c
> @@ -2764,7 +2764,7 @@ qemu_loadvm_section_start_full(QEMUFile *f, uint8_t type, Error **errp)
>  }
>  
>  static int
> -qemu_loadvm_section_part_end(QEMUFile *f, uint8_t type)
> +qemu_loadvm_section_part_end(QEMUFile *f, uint8_t type, Error **errp)
>  {
>      bool trace_downtime = (type == QEMU_VM_SECTION_END);
>      int64_t start_ts, end_ts;
> @@ -2776,8 +2776,8 @@ qemu_loadvm_section_part_end(QEMUFile *f, uint8_t type)
>  
>      ret = qemu_file_get_error(f);
>      if (ret) {
> -        error_report("%s: Failed to read section ID: %d",
> -                     __func__, ret);
> +        error_setg(errp, "%s: Failed to read section ID: %d",
> +                   __func__, ret);

Same note about dropping __func__

> @@ -2810,6 +2810,7 @@ qemu_loadvm_section_part_end(QEMUFile *f, uint8_t type)
>      }
>  
>      if (!check_section_footer(f, se)) {
> +        error_setg(errp, "Check section footer error");

Include "section_id" as that's the only context we have available.

>          return -EINVAL;
>      }
>  

With regards,
Daniel
-- 
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Re: [PATCH v5 07/23] migration: push Error **errp into loadvm_process_command()

[Daniel P. Berrangé]

On Thu, Jul 17, 2025 at 06:07:30AM +0530, 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 loadvm_process_command() must report an error
> in errp, in case of failure.
> 
> Signed-off-by: Arun Menon <armenon@redhat.com>
> ---
>  migration/savevm.c | 89 ++++++++++++++++++++++++++++++++++++++++--------------
>  1 file changed, 67 insertions(+), 22 deletions(-)
> 
> diff --git a/migration/savevm.c b/migration/savevm.c
> index 22d73999595384519c755c9416b74ba1263a8bb9..98711bb38a4548d4f168459f729f604a78716c25 100644
> --- a/migration/savevm.c
> +++ b/migration/savevm.c
> @@ -2540,12 +2540,13 @@ static int loadvm_postcopy_handle_switchover_start(void)
>   * LOADVM_QUIT All good, but exit the loop
>   * <0          Error
>   */
> -static int loadvm_process_command(QEMUFile *f)
> +static int loadvm_process_command(QEMUFile *f, Error **errp)
>  {
>      MigrationIncomingState *mis = migration_incoming_get_current();
>      uint16_t cmd;
>      uint16_t len;
>      uint32_t tmp32;
> +    int ret;
>  
>      cmd = qemu_get_be16(f);
>      len = qemu_get_be16(f);
> @@ -2556,16 +2557,16 @@ static int loadvm_process_command(QEMUFile *f)
>      }
>  
>      if (cmd >= MIG_CMD_MAX || cmd == MIG_CMD_INVALID) {
> -        error_report("MIG_CMD 0x%x unknown (len 0x%x)", cmd, len);
> +        error_setg(errp, "MIG_CMD 0x%x unknown (len 0x%x)", cmd, len);
>          return -EINVAL;
>      }
>  


> @@ -2578,7 +2579,7 @@ static int loadvm_process_command(QEMUFile *f)
>          }
>          mis->to_src_file = qemu_file_get_return_path(f);
>          if (!mis->to_src_file) {
> -            error_report("CMD_OPEN_RETURN_PATH failed");
> +            error_setg(errp, "CMD_OPEN_RETURN_PATH failed");

This is a wierd one, according to the docs qemu_file_get_return_path
can return NULL, but according to the impl it will always succeed.

Suggest creating an earlier patch that fixes the docs and removes
the check for failure here, not least because this existing error
message provides no useful information, and none will be available
since it can't fail.


>      case MIG_CMD_PACKAGED:
> -        return loadvm_handle_cmd_packaged(mis);
> +        ret = loadvm_handle_cmd_packaged(mis);
> +        if (ret < 0) {
> +            error_setg(errp, "Failed to load device state command: %d", ret);
> +            return -1;
> +        }
> +        return ret;
>  
>      case MIG_CMD_POSTCOPY_ADVISE:
> -        return loadvm_postcopy_handle_advise(mis, len);
> +        ret = loadvm_postcopy_handle_advise(mis, len);
> +        if (ret < 0) {
> +            error_setg(errp, "Failed to load device state command: %d", ret);
> +            return -1;
> +        }
> +        return ret;
>  
>      case MIG_CMD_POSTCOPY_LISTEN:
> -        return loadvm_postcopy_handle_listen(mis);
> +        ret = loadvm_postcopy_handle_listen(mis);
> +        if (ret < 0) {
> +            error_setg(errp, "Failed to load device state command: %d", ret);
> +            return -1;
> +        }
> +        return ret;
>  
>      case MIG_CMD_POSTCOPY_RUN:
> -        return loadvm_postcopy_handle_run(mis);
> +        ret = loadvm_postcopy_handle_run(mis);
> +        if (ret < 0) {
> +            error_setg(errp, "Failed to load device state command: %d", ret);
> +            return -1;
> +        }
> +        return ret;
>  
>      case MIG_CMD_POSTCOPY_RAM_DISCARD:
> -        return loadvm_postcopy_ram_handle_discard(mis, len);
> +        ret = loadvm_postcopy_ram_handle_discard(mis, len);
> +        if (ret < 0) {
> +            error_setg(errp, "Failed to load device state command: %d", ret);
> +            return -1;
> +        }
> +        return ret;
>  
>      case MIG_CMD_POSTCOPY_RESUME:
> -        return loadvm_postcopy_handle_resume(mis);
> +        ret = loadvm_postcopy_handle_resume(mis);
> +        if (ret < 0) {
> +            error_setg(errp, "Failed to load device state command: %d", ret);
> +            return -1;
> +        }
> +        return ret;
>  
>      case MIG_CMD_RECV_BITMAP:
> -        return loadvm_handle_recv_bitmap(mis, len);
> +        ret = loadvm_handle_recv_bitmap(mis, len);
> +        if (ret < 0) {
> +            error_setg(errp, "Failed to load device state command: %d", ret);
> +            return -1;
> +        }
> +        return ret;
>  
>      case MIG_CMD_ENABLE_COLO:
> -        return loadvm_process_enable_colo(mis);
> +        ret = loadvm_process_enable_colo(mis);
> +        if (ret < 0) {
> +            error_setg(errp, "Failed to load device state command: %d", ret);
> +            return -1;
> +        }
> +        return ret;
>  
>      case MIG_CMD_SWITCHOVER_START:
> -        return loadvm_postcopy_handle_switchover_start();
> +        ret = loadvm_postcopy_handle_switchover_start();
> +        if (ret < 0) {
> +            error_setg(errp, "Failed to load device state command: %d", ret);
> +            return -1;
> +        }
> +        return ret;
>      }

Can you ensure that each of these have unique error message strings,
as if they ever appear, it will be important to distinguish which of
these nine commands actually failed.


With regards,
Daniel
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Re: [PATCH v5 08/23] migration: push Error **errp into loadvm_handle_cmd_packaged()

[Daniel P. Berrangé]

On Thu, Jul 17, 2025 at 06:07:31AM +0530, 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 loadvm_handle_cmd_packaged() must report an error
> in errp, in case of failure.
> 
> Signed-off-by: Arun Menon <armenon@redhat.com>
> ---
>  migration/savevm.c | 18 ++++++++----------
>  1 file changed, 8 insertions(+), 10 deletions(-)

Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>


With regards,
Daniel
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Re: [PATCH v5 09/23] migration: push Error **errp into ram_postcopy_incoming_init()

[Daniel P. Berrangé]

On Thu, Jul 17, 2025 at 12:34:21PM +0900, Akihiko Odaki wrote:
> On 2025/07/17 9:37, 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 ram_postcopy_incoming_init() must report an error
> > in errp, in case of failure.
> > 
> > Signed-off-by: Arun Menon <armenon@redhat.com>
> > ---
> >   migration/postcopy-ram.c | 9 ++++++---
> >   migration/postcopy-ram.h | 2 +-
> >   migration/ram.c          | 6 +++---
> >   migration/ram.h          | 2 +-
> >   migration/savevm.c       | 2 +-
> >   5 files changed, 12 insertions(+), 9 deletions(-)
> > 
> > diff --git a/migration/postcopy-ram.c b/migration/postcopy-ram.c
> > index 45af9a361e8eacaad0fb217a5da2c5004416c1da..05617e5fbcad62226a54fe17d9f7d9a316baf1e4 100644
> > --- a/migration/postcopy-ram.c
> > +++ b/migration/postcopy-ram.c
> > @@ -681,6 +681,7 @@ out:
> >    */
> >   static int init_range(RAMBlock *rb, void *opaque)
> >   {
> > +    Error **errp = opaque;
> >       const char *block_name = qemu_ram_get_idstr(rb);
> >       void *host_addr = qemu_ram_get_host_addr(rb);
> >       ram_addr_t offset = qemu_ram_get_offset(rb);
> > @@ -701,6 +702,8 @@ static int init_range(RAMBlock *rb, void *opaque)
> >        * (Precopy will just overwrite this data, so doesn't need the discard)
> >        */
> >       if (ram_discard_range(block_name, 0, length)) {
> > +        error_setg(errp, "failed to discard RAM block %s len=%zu",
> > +                   block_name, length);
> >           return -1;
> >       }
> > @@ -749,9 +752,9 @@ static int cleanup_range(RAMBlock *rb, void *opaque)
> >    * postcopy later; must be called prior to any precopy.
> >    * called from arch_init's similarly named ram_postcopy_incoming_init
> >    */
> > -int postcopy_ram_incoming_init(MigrationIncomingState *mis)
> > +int postcopy_ram_incoming_init(MigrationIncomingState *mis, Error **errp)
> >   {
> > -    if (foreach_not_ignored_block(init_range, NULL)) {
> > +    if (foreach_not_ignored_block(init_range, errp)) {
> >           return -1;
> >       }
> > @@ -1703,7 +1706,7 @@ bool postcopy_ram_supported_by_host(MigrationIncomingState *mis, Error **errp)
> >       return false;
> >   }
> > -int postcopy_ram_incoming_init(MigrationIncomingState *mis)
> > +int postcopy_ram_incoming_init(MigrationIncomingState *mis, Error **errp)
> >   {
> >       error_report("postcopy_ram_incoming_init: No OS support");
> >       return -1;
> > diff --git a/migration/postcopy-ram.h b/migration/postcopy-ram.h
> > index 3852141d7e37ab18bada4b46c137fef0969d0070..ca19433b246893fa5105bcebffb442c58a9a4f48 100644
> > --- a/migration/postcopy-ram.h
> > +++ b/migration/postcopy-ram.h
> > @@ -30,7 +30,7 @@ int postcopy_ram_incoming_setup(MigrationIncomingState *mis);
> >    * postcopy later; must be called prior to any precopy.
> >    * called from ram.c's similarly named ram_postcopy_incoming_init
> >    */
> > -int postcopy_ram_incoming_init(MigrationIncomingState *mis);
> > +int postcopy_ram_incoming_init(MigrationIncomingState *mis, Error **errp);
> >   /*
> >    * At the end of a migration where postcopy_ram_incoming_init was called.
> > diff --git a/migration/ram.c b/migration/ram.c
> > index 7208bc114fb5c366740db380ee6956a91b3871a0..8223183132dc0f558f45fbae3f4f832845730bd3 100644
> > --- a/migration/ram.c
> > +++ b/migration/ram.c
> > @@ -3708,7 +3708,7 @@ static int ram_load_cleanup(void *opaque)
> >   /**
> >    * ram_postcopy_incoming_init: allocate postcopy data structures
> >    *
> > - * Returns 0 for success and negative if there was one error
> > + * Returns 0 for success and -1 if there was one error
> 
> This is true but not relevant in this patch's goal.
> 
> Besides, I'm not in favor of letting callers make an assumption on integer
> return values (i.e., let callers assume a particular integer value in the
> error conditions). It is subtle to make a mistake to return -errno while the
> documentation says it returns -1.

In general I would consider it bad practice to have an method
with "Error **errp" that also returns an errno. 95% of the time
the errno is just there as further info on the error scenario,
which "errp" obsoletes. Only in the rare cases where the caller
needs to take functional action based on errno values, is it
appropriate to contine returning '-errno'.

IOW, I'd consider this appropriate for the patch as is.

> I think a proper way to avoid bugs due to return values here is to change
> the type to bool, which ensures there are two possible values; that is a
> nice improvement but something that can be done later.

That doesn't guarantee avoidance of bugs, as bool values can be
assigned to & compared against integers.


> > diff --git a/migration/savevm.c b/migration/savevm.c
> > index d1edeaac5f2a5df2f6d94357388be807a938b2ef..8eba151a693b7f2dc58853292c92024288eae81e 100644
> > --- a/migration/savevm.c
> > +++ b/migration/savevm.c
> > @@ -1983,7 +1983,7 @@ static int loadvm_postcopy_handle_advise(MigrationIncomingState *mis,
> >           return -1;
> >       }
> > -    if (ram_postcopy_incoming_init(mis)) {
> > +    if (ram_postcopy_incoming_init(mis, NULL)) {
> >           return -1;
> >       }

This is a definite anti-pattern though as it treats positive return
values as errors, contrary to the documented API  for both the old
and new code.

So change this to "< 0" while we're here.


With regards,
Daniel
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Re: [PATCH v5 10/23] migration: push Error **errp into loadvm_postcopy_handle_advise()

[Daniel P. Berrangé]

On Thu, Jul 17, 2025 at 06:07:33AM +0530, 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 loadvm_postcopy_handle_advise() must report an error
> in errp, in case of failure.
> 
> Signed-off-by: Arun Menon <armenon@redhat.com>
> ---
>  migration/savevm.c | 39 +++++++++++++++++----------------------
>  1 file changed, 17 insertions(+), 22 deletions(-)

Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>


With regards,
Daniel
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Re: [PATCH v5 11/23] migration: push Error **errp into loadvm_postcopy_handle_listen()

[Daniel P. Berrangé]

On Thu, Jul 17, 2025 at 06:07:34AM +0530, 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 loadvm_postcopy_handle_listen() must report an error
> in errp, in case of failure.
> 
> Signed-off-by: Arun Menon <armenon@redhat.com>
> ---
>  migration/savevm.c | 18 +++++++-----------
>  1 file changed, 7 insertions(+), 11 deletions(-)

Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>


With regards,
Daniel
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Re: [PATCH v5 12/23] migration: push Error **errp into loadvm_postcopy_handle_run()

[Daniel P. Berrangé]

On Thu, Jul 17, 2025 at 06:07:35AM +0530, 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 loadvm_postcopy_handle_run() must report an error
> in errp, in case of failure.
> 
> Signed-off-by: Arun Menon <armenon@redhat.com>
> ---
>  migration/savevm.c | 12 ++++--------
>  1 file changed, 4 insertions(+), 8 deletions(-)


Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>


With regards,
Daniel
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Re: [PATCH v5 14/23] migration: make loadvm_postcopy_handle_resume() void

[Daniel P. Berrangé]

On Thu, Jul 17, 2025 at 06:07:37AM +0530, 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.
> 
> Signed-off-by: Arun Menon <armenon@redhat.com>
> ---
>  migration/savevm.c | 14 ++++----------
>  1 file changed, 4 insertions(+), 10 deletions(-)

> diff --git a/migration/savevm.c b/migration/savevm.c
> index 6f181c381dc6ecd996a1f8dbc25cceead7ebe014..20dce4b43a181d2f47b6b22e7a15aa4fc45cac5c 100644
> --- a/migration/savevm.c
> +++ b/migration/savevm.c
> @@ -2333,12 +2333,12 @@ static void migrate_send_rp_req_pages_pending(MigrationIncomingState *mis)
>      }
>  }
>  
> -static int loadvm_postcopy_handle_resume(MigrationIncomingState *mis)
> +static void loadvm_postcopy_handle_resume(MigrationIncomingState *mis)
>  {
>      if (mis->state != MIGRATION_STATUS_POSTCOPY_RECOVER) {
>          error_report("%s: illegal resume received", __func__);

Pre-existing mistake, but can you change this to 'warn_report' given that
we're not treating it as an error.


Aside from that

Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>


With regards,
Daniel
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Re: [PATCH v5 07/23] migration: push Error **errp into loadvm_process_command()

[Daniel P. Berrangé]

On Thu, Jul 17, 2025 at 05:54:41PM +0100, Daniel P. Berrangé wrote:
> On Thu, Jul 17, 2025 at 06:07:30AM +0530, 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 loadvm_process_command() must report an error
> > in errp, in case of failure.
> > 
> > Signed-off-by: Arun Menon <armenon@redhat.com>
> > ---
> >  migration/savevm.c | 89 ++++++++++++++++++++++++++++++++++++++++--------------
> >  1 file changed, 67 insertions(+), 22 deletions(-)
> > 
> > diff --git a/migration/savevm.c b/migration/savevm.c
> > index 22d73999595384519c755c9416b74ba1263a8bb9..98711bb38a4548d4f168459f729f604a78716c25 100644
> > --- a/migration/savevm.c
> > +++ b/migration/savevm.c

> >      case MIG_CMD_PACKAGED:
> > -        return loadvm_handle_cmd_packaged(mis);
> > +        ret = loadvm_handle_cmd_packaged(mis);
> > +        if (ret < 0) {
> > +            error_setg(errp, "Failed to load device state command: %d", ret);
> > +            return -1;
> > +        }
> > +        return ret;
> >  
> >      case MIG_CMD_POSTCOPY_ADVISE:
> > -        return loadvm_postcopy_handle_advise(mis, len);
> > +        ret = loadvm_postcopy_handle_advise(mis, len);
> > +        if (ret < 0) {
> > +            error_setg(errp, "Failed to load device state command: %d", ret);
> > +            return -1;
> > +        }
> > +        return ret;
> >  
> >      case MIG_CMD_POSTCOPY_LISTEN:
> > -        return loadvm_postcopy_handle_listen(mis);
> > +        ret = loadvm_postcopy_handle_listen(mis);
> > +        if (ret < 0) {
> > +            error_setg(errp, "Failed to load device state command: %d", ret);
> > +            return -1;
> > +        }
> > +        return ret;
> >  
> >      case MIG_CMD_POSTCOPY_RUN:
> > -        return loadvm_postcopy_handle_run(mis);
> > +        ret = loadvm_postcopy_handle_run(mis);
> > +        if (ret < 0) {
> > +            error_setg(errp, "Failed to load device state command: %d", ret);
> > +            return -1;
> > +        }
> > +        return ret;
> >  
> >      case MIG_CMD_POSTCOPY_RAM_DISCARD:
> > -        return loadvm_postcopy_ram_handle_discard(mis, len);
> > +        ret = loadvm_postcopy_ram_handle_discard(mis, len);
> > +        if (ret < 0) {
> > +            error_setg(errp, "Failed to load device state command: %d", ret);
> > +            return -1;
> > +        }
> > +        return ret;
> >  
> >      case MIG_CMD_POSTCOPY_RESUME:
> > -        return loadvm_postcopy_handle_resume(mis);
> > +        ret = loadvm_postcopy_handle_resume(mis);
> > +        if (ret < 0) {
> > +            error_setg(errp, "Failed to load device state command: %d", ret);
> > +            return -1;
> > +        }
> > +        return ret;
> >  
> >      case MIG_CMD_RECV_BITMAP:
> > -        return loadvm_handle_recv_bitmap(mis, len);
> > +        ret = loadvm_handle_recv_bitmap(mis, len);
> > +        if (ret < 0) {
> > +            error_setg(errp, "Failed to load device state command: %d", ret);
> > +            return -1;
> > +        }
> > +        return ret;
> >  
> >      case MIG_CMD_ENABLE_COLO:
> > -        return loadvm_process_enable_colo(mis);
> > +        ret = loadvm_process_enable_colo(mis);
> > +        if (ret < 0) {
> > +            error_setg(errp, "Failed to load device state command: %d", ret);
> > +            return -1;
> > +        }
> > +        return ret;
> >  
> >      case MIG_CMD_SWITCHOVER_START:
> > -        return loadvm_postcopy_handle_switchover_start();
> > +        ret = loadvm_postcopy_handle_switchover_start();
> > +        if (ret < 0) {
> > +            error_setg(errp, "Failed to load device state command: %d", ret);
> > +            return -1;
> > +        }
> > +        return ret;
> >      }
> 
> Can you ensure that each of these have unique error message strings,
> as if they ever appear, it will be important to distinguish which of
> these nine commands actually failed.

Ignore this comment. I see you eliminate all these generic error messages
in following patches, so this is only ever a transient issue half way
through the patch series.


With regards,
Daniel
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Re: [PATCH v5 15/23] migration: push Error **errp into loadvm_handle_recv_bitmap()

[Daniel P. Berrangé]

On Thu, Jul 17, 2025 at 06:07:38AM +0530, 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 loadvm_handle_recv_bitmap() must report an error
> in errp, in case of failure.
> 
> Signed-off-by: Arun Menon <armenon@redhat.com>
> ---
>  migration/savevm.c | 22 ++++++++++------------
>  1 file changed, 10 insertions(+), 12 deletions(-)

Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>

> 
> diff --git a/migration/savevm.c b/migration/savevm.c
> index 20dce4b43a181d2f47b6b22e7a15aa4fc45cac5c..1cbc44a5314043a403d983511066cf137681a18d 100644
> --- a/migration/savevm.c
> +++ b/migration/savevm.c
> @@ -2471,32 +2471,35 @@ static int loadvm_handle_cmd_packaged(MigrationIncomingState *mis, Error **errp)
>   * len (1 byte) + ramblock_name (<255 bytes)
>   */
>  static int loadvm_handle_recv_bitmap(MigrationIncomingState *mis,
> -                                     uint16_t len)
> +                                     uint16_t len, Error **errp)
>  {
>      QEMUFile *file = mis->from_src_file;
>      RAMBlock *rb;
>      char block_name[256];
>      size_t cnt;
> +    int ret;
>  
>      cnt = qemu_get_counted_string(file, block_name);
>      if (!cnt) {
> -        error_report("%s: failed to read block name", __func__);
> +        error_setg(errp, "%s: failed to read block name", __func__);
>          return -EINVAL;
>      }
>  
>      /* Validate before using the data */
> -    if (qemu_file_get_error(file)) {
> -        return qemu_file_get_error(file);
> +    ret = qemu_file_get_error(file);
> +    if (ret < 0) {
> +        error_setg(errp, "migration stream has error: %d", ret);
> +        return ret;
>      }
>  
>      if (len != cnt + 1) {
> -        error_report("%s: invalid payload length (%d)", __func__, len);
> +        error_setg(errp, "%s: invalid payload length (%d)", __func__, len);
>          return -EINVAL;
>      }
>  
>      rb = qemu_ram_block_by_name(block_name);
>      if (!rb) {
> -        error_report("%s: block '%s' not found", __func__, block_name);
> +        error_setg(errp, "%s: block '%s' not found", __func__, block_name);
>          return -EINVAL;
>      }

(Pre-existing) redundant use of __func__ that can be removed.

Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>


With regards,
Daniel
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Re: [PATCH v5 17/23] migration: push Error **errp into loadvm_postcopy_handle_switchover_start()

[Daniel P. Berrangé]

On Thu, Jul 17, 2025 at 06:07:40AM +0530, 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 loadvm_postcopy_handle_switchover_start() must report
> an error in errp, in case of failure.
> 
> Signed-off-by: Arun Menon <armenon@redhat.com>
> ---
>  migration/savevm.c | 10 +++-------
>  1 file changed, 3 insertions(+), 7 deletions(-)

Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>


With regards,
Daniel
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Re: [PATCH v5 18/23] migration: push Error **errp into qemu_loadvm_state_main()

[Daniel P. Berrangé]

On Thu, Jul 17, 2025 at 06:07:41AM +0530, 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 qemu_loadvm_state_main() must report an error
> in errp, in case of failure.
> loadvm_process_command also sets the errp object explicitly.
> 
> Signed-off-by: Arun Menon <armenon@redhat.com>
> ---
>  migration/colo.c   |  5 +++--
>  migration/savevm.c | 23 +++++++++++++----------
>  migration/savevm.h |  3 ++-
>  3 files changed, 18 insertions(+), 13 deletions(-)

Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>


> 
> diff --git a/migration/colo.c b/migration/colo.c
> index e0f713c837f5da25d67afbd02ceb6c54024ca3af..ddc628cab4194b3cb82388c5e878286c820004b2 100644
> --- a/migration/colo.c
> +++ b/migration/colo.c
> @@ -686,11 +686,12 @@ static void colo_incoming_process_checkpoint(MigrationIncomingState *mis,
>  
>      bql_lock();
>      cpu_synchronize_all_states();
> -    ret = qemu_loadvm_state_main(mis->from_src_file, mis);
> +    ret = qemu_loadvm_state_main(mis->from_src_file, mis, &local_err);

Although earlier code in this method is using "&local_err", that
it because those methods are "void" return, so checking 'local_err'
is needed to detect failure.

In this case, however, you use 'ret' to detect failure so passing
"errp" to this method directly is the correct pattern....

>      bql_unlock();
>  
>      if (ret < 0) {
> -        error_setg(errp, "Load VM's live state (ram) error");
> +        error_propagate_prepend(errp, local_err,
> +                                "Load VM's live state (ram) error");

..and just error_prepend here.


> @@ -3055,7 +3055,8 @@ static bool postcopy_pause_incoming(MigrationIncomingState *mis)
>      return true;
>  }
>  
> -int qemu_loadvm_state_main(QEMUFile *f, MigrationIncomingState *mis)
> +int qemu_loadvm_state_main(QEMUFile *f, MigrationIncomingState *mis,
> +                           Error **errp)
>  {
>      uint8_t section_type;
>      int ret = 0;
> @@ -3066,6 +3067,8 @@ retry:
>  
>          ret = qemu_file_get_error_obj_any(f, mis->postcopy_qemufile_dst, NULL);
>          if (ret) {
> +            error_setg(errp, "Failed to load device state section ID : %d",
> +                       ret);

Pass "errp" to qemu_file_get_error_obj_any() instead of NULL, to get the
real pre-existing error message.


With regards,
Daniel
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Re: [PATCH v5 19/23] migration: push Error **errp into qemu_loadvm_state()

[Daniel P. Berrangé]

On Thu, Jul 17, 2025 at 06:07:42AM +0530, 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 qemu_loadvm_state() must report an error
> in errp, in case of failure.
> 
> Signed-off-by: Arun Menon <armenon@redhat.com>
> ---
>  migration/migration.c |  5 +++--
>  migration/savevm.c    | 25 +++++++++++++------------
>  migration/savevm.h    |  2 +-
>  3 files changed, 17 insertions(+), 15 deletions(-)


> @@ -3181,8 +3178,12 @@ int qemu_loadvm_state(QEMUFile *f)
>          if (migrate_has_error(migrate_get_current()) ||
>              !qemu_loadvm_thread_pool_wait(s, mis)) {
>              ret = -EINVAL;
> +            error_setg(errp, "Error while loading vmstate : %d", ret);
>          } else {
>              ret = qemu_file_get_error(f);
> +            if (ret < 0) {
> +                error_setg(errp, "Error while loading vmstate : %d", ret);
> +            }

Replace qemu_file_get_error with qemu_file_get_error_obj(..., errp)
so we propagate the real error message.


With regards,
Daniel
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Re: [PATCH v5 20/23] migration: push Error **errp into qemu_load_device_state()

[Daniel P. Berrangé]

On Thu, Jul 17, 2025 at 06:07:43AM +0530, 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 qemu_load_device_state() must report an error
> in errp, in case of failure.
> 
> Signed-off-by: Arun Menon <armenon@redhat.com>
> ---
>  migration/colo.c   | 5 +++--
>  migration/savevm.c | 6 +++---
>  migration/savevm.h | 2 +-
>  3 files changed, 7 insertions(+), 6 deletions(-)
> 
> diff --git a/migration/colo.c b/migration/colo.c
> index ddc628cab4194b3cb82388c5e878286c820004b2..7291df0d47d8e308f8b71973c908b5a05ec7f4d7 100644
> --- a/migration/colo.c
> +++ b/migration/colo.c
> @@ -730,9 +730,10 @@ static void colo_incoming_process_checkpoint(MigrationIncomingState *mis,
>      bql_lock();
>      vmstate_loading = true;
>      colo_flush_ram_cache();
> -    ret = qemu_load_device_state(fb);
> +    ret = qemu_load_device_state(fb, &local_err);

Just use 'errp' here

>      if (ret < 0) {
> -        error_setg(errp, "COLO: load device state failed");
> +        error_propagate_prepend(errp, local_err,
> +                                "COLO: load device state failed");
>          vmstate_loading = false;
>          bql_unlock();
>          return;

With regards,
Daniel
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Re: [PATCH v5 21/23] migration: Capture error in postcopy_ram_listen_thread()

[Daniel P. Berrangé]

On Thu, Jul 17, 2025 at 06:07:44AM +0530, 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.
> postcopy_ram_listen_thread() calls qemu_loadvm_state_main()
> to load the vm, and in case of a failure, it should set the error
> in the migration object.
> 
> When postcopy live migration runs, the device states are loaded by
> both the qemu coroutine process_incoming_migration_co() and the
> postcopy_ram_listen_thread(). Therefore, it is important that the
> coroutine also reports the error in case of failure, with
> error_report_err(). Otherwise, the source qemu will not display
> any errors before going into the postcopy pause state.
> 
> Signed-off-by: Arun Menon <armenon@redhat.com>
> ---
>  migration/migration.c |  2 +-
>  migration/savevm.c    | 10 ++++++++--
>  2 files changed, 9 insertions(+), 3 deletions(-)
> 


> diff --git a/migration/savevm.c b/migration/savevm.c
> index 0fff65c96344c65191353311e72730cd6e3bfb23..4f67eebe5321c175d51e8029e36ceb336c98ad1f 100644
> --- a/migration/savevm.c
> +++ b/migration/savevm.c
> @@ -2086,6 +2086,7 @@ static void *postcopy_ram_listen_thread(void *opaque)
>      QEMUFile *f = mis->from_src_file;
>      int load_res;
>      MigrationState *migr = migrate_get_current();
> +    Error *local_err = NULL;
>  
>      object_ref(OBJECT(migr));
>  
> @@ -2102,7 +2103,7 @@ static void *postcopy_ram_listen_thread(void *opaque)
>      qemu_file_set_blocking(f, true);
>  
>      /* TODO: sanity check that only postcopiable data will be loaded here */
> -    load_res = qemu_loadvm_state_main(f, mis, NULL);
> +    load_res = qemu_loadvm_state_main(f, mis, &local_err);
>  
>      /*
>       * This is tricky, but, mis->from_src_file can change after it
> @@ -2128,7 +2129,12 @@ static void *postcopy_ram_listen_thread(void *opaque)
>                           __func__, load_res);
>              load_res = 0; /* prevent further exit() */
>          } else {
> -            error_report("%s: loadvm failed: %d", __func__, load_res);
> +            if (local_err != NULL) {
> +                error_prepend(&local_err, "%s: loadvm failed: %d", __func__,
> +                              load_res);

IMHO __func__ is redundant if you change the message
to be 'loadvm failed during postcopy' like the earlier part
fo the "if { " does.

> +                migrate_set_error(migr, local_err);
> +                error_report_err(local_err);
> +            }
>              migrate_set_state(&mis->state, MIGRATION_STATUS_POSTCOPY_ACTIVE,
>                                             MIGRATION_STATUS_FAILED);

With regards,
Daniel
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Re: [PATCH v5 22/23] migration: Add error-parameterized function variants in VMSD struct

[Daniel P. Berrangé]

On Thu, Jul 17, 2025 at 06:07:45AM +0530, Arun Menon wrote:
> - We need to have good error reporting in the callbacks in
>   VMStateDescription struct. Specifically pre_save, post_save,
>   pre_load and post_load callbacks.
> - It is not possible to change these functions everywhere in one
>   patch, therefore, we introduce a duplicate set of callbacks
>   with Error object passed to them.
> - So, in this commit, we implement 'errp' variants of these callbacks,
>   introducing an explicit Error object parameter.
> - This is a functional step towards transitioning the entire codebase
>   to the new error-parameterized functions.
> - Deliberately called in mutual exclusion from their counterparts,
>   to prevent conflicts during the transition.
> - New impls should preferentally use 'errp' variants of
>   these methods, and existing impls incrementally converted.
>   The variants without 'errp' are intended to be removed
>   once all usage is converted.
> 
> Signed-off-by: Arun Menon <armenon@redhat.com>
> ---
>  include/migration/vmstate.h | 11 +++++++++++
>  migration/vmstate.c         | 36 +++++++++++++++++++++++++++++++-----
>  2 files changed, 42 insertions(+), 5 deletions(-)


> @@ -524,7 +542,9 @@ int vmstate_save_state_v(QEMUFile *f, const VMStateDescription *vmsd,
>                  if (ret) {
>                      error_setg(errp, "Save of field %s/%s failed",
>                                  vmsd->name, field->name);
> -                    if (vmsd->post_save) {
> +                    if (vmsd->post_save_errp) {
> +                        vmsd->post_save_errp(opaque, errp);

We are already in an error path here, and we set 'errp' just a few lines
above. If post_save_errp tries to set it too, then we're doomed.

You'll need to pass an &Local_err in here, and then append it to the
current error.

> +                    } else if (vmsd->post_save) {
>                          vmsd->post_save(opaque);
>                      }
>                      return ret;
> @@ -552,7 +572,13 @@ int vmstate_save_state_v(QEMUFile *f, const VMStateDescription *vmsd,
>  
>      ret = vmstate_subsection_save(f, vmsd, opaque, vmdesc, errp);


Potentially set 'errp'



> -    if (vmsd->post_save) {
> +    if (vmsd->post_save_errp) {
> +        int ps_ret = vmsd->post_save_errp(opaque, errp);

so must not be passing 'errp' here.

> +        if (!ret && ps_ret) {
> +            ret = ps_ret;
> +            error_prepend(errp, "post-save failed: %s ", vmsd->name);
> +        }


> +    } else if (vmsd->post_save) {
>          int ps_ret = vmsd->post_save(opaque);
>          if (!ret && ps_ret) {
>              ret = ps_ret;
> 
> -- 
> 2.50.0
> 
> 

With regards,
Daniel
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Re: [PATCH v5 23/23] backends/tpm: Propagate vTPM error on migration failure

[Daniel P. Berrangé]

On Thu, Jul 17, 2025 at 06:07:46AM +0530, Arun Menon wrote:
> - When migration of a VM with encrypted vTPM fails on the
>   destination host, (e.g., due to a mismatch in secret values),
>   the error message displayed on the source host is generic and unhelpful.
> - For example, a typical error looks like this:
>   "operation failed: job 'migration out' failed: Sibling indicated error 1.
>   operation failed: job 'migration in' failed: load of migration failed:
>   Input/output error"
> - Such generic errors are logged using error_report(), which prints to
>   the console/monitor but does not make the detailed error accessible via
>   the QMP query-migrate command.
> - This change, along with the set of changes of passing errp Error object
>   to the VM state loading functions, help in addressing the issue.
>   We use the post_load_errp hook of VMStateDescription to propagate errors
>   by setting Error **errp objects in case of failure in the TPM backend.
> - It can then be retrieved using QMP command:
>   {"execute" : "query-migrate"}
> 
> Buglink: https://issues.redhat.com/browse/RHEL-82826
> 
> Reviewed-by: Stefan Berger <stefanb@linux.ibm.com>
> Signed-off-by: Arun Menon <armenon@redhat.com>
> ---
>  backends/tpm/tpm_emulator.c | 39 ++++++++++++++++++++-------------------
>  1 file changed, 20 insertions(+), 19 deletions(-)

Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>


With regards,
Daniel
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Re: [PATCH v5 09/23] migration: push Error **errp into ram_postcopy_incoming_init()

[Akihiko Odaki]

On 2025/07/18 2:02, Daniel P. Berrangé wrote:
> On Thu, Jul 17, 2025 at 12:34:21PM +0900, Akihiko Odaki wrote:
>> On 2025/07/17 9:37, 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 ram_postcopy_incoming_init() must report an error
>>> in errp, in case of failure.
>>>
>>> Signed-off-by: Arun Menon <armenon@redhat.com>
>>> ---
>>>    migration/postcopy-ram.c | 9 ++++++---
>>>    migration/postcopy-ram.h | 2 +-
>>>    migration/ram.c          | 6 +++---
>>>    migration/ram.h          | 2 +-
>>>    migration/savevm.c       | 2 +-
>>>    5 files changed, 12 insertions(+), 9 deletions(-)
>>>
>>> diff --git a/migration/postcopy-ram.c b/migration/postcopy-ram.c
>>> index 45af9a361e8eacaad0fb217a5da2c5004416c1da..05617e5fbcad62226a54fe17d9f7d9a316baf1e4 100644
>>> --- a/migration/postcopy-ram.c
>>> +++ b/migration/postcopy-ram.c
>>> @@ -681,6 +681,7 @@ out:
>>>     */
>>>    static int init_range(RAMBlock *rb, void *opaque)
>>>    {
>>> +    Error **errp = opaque;
>>>        const char *block_name = qemu_ram_get_idstr(rb);
>>>        void *host_addr = qemu_ram_get_host_addr(rb);
>>>        ram_addr_t offset = qemu_ram_get_offset(rb);
>>> @@ -701,6 +702,8 @@ static int init_range(RAMBlock *rb, void *opaque)
>>>         * (Precopy will just overwrite this data, so doesn't need the discard)
>>>         */
>>>        if (ram_discard_range(block_name, 0, length)) {
>>> +        error_setg(errp, "failed to discard RAM block %s len=%zu",
>>> +                   block_name, length);
>>>            return -1;
>>>        }
>>> @@ -749,9 +752,9 @@ static int cleanup_range(RAMBlock *rb, void *opaque)
>>>     * postcopy later; must be called prior to any precopy.
>>>     * called from arch_init's similarly named ram_postcopy_incoming_init
>>>     */
>>> -int postcopy_ram_incoming_init(MigrationIncomingState *mis)
>>> +int postcopy_ram_incoming_init(MigrationIncomingState *mis, Error **errp)
>>>    {
>>> -    if (foreach_not_ignored_block(init_range, NULL)) {
>>> +    if (foreach_not_ignored_block(init_range, errp)) {
>>>            return -1;
>>>        }
>>> @@ -1703,7 +1706,7 @@ bool postcopy_ram_supported_by_host(MigrationIncomingState *mis, Error **errp)
>>>        return false;
>>>    }
>>> -int postcopy_ram_incoming_init(MigrationIncomingState *mis)
>>> +int postcopy_ram_incoming_init(MigrationIncomingState *mis, Error **errp)
>>>    {
>>>        error_report("postcopy_ram_incoming_init: No OS support");
>>>        return -1;
>>> diff --git a/migration/postcopy-ram.h b/migration/postcopy-ram.h
>>> index 3852141d7e37ab18bada4b46c137fef0969d0070..ca19433b246893fa5105bcebffb442c58a9a4f48 100644
>>> --- a/migration/postcopy-ram.h
>>> +++ b/migration/postcopy-ram.h
>>> @@ -30,7 +30,7 @@ int postcopy_ram_incoming_setup(MigrationIncomingState *mis);
>>>     * postcopy later; must be called prior to any precopy.
>>>     * called from ram.c's similarly named ram_postcopy_incoming_init
>>>     */
>>> -int postcopy_ram_incoming_init(MigrationIncomingState *mis);
>>> +int postcopy_ram_incoming_init(MigrationIncomingState *mis, Error **errp);
>>>    /*
>>>     * At the end of a migration where postcopy_ram_incoming_init was called.
>>> diff --git a/migration/ram.c b/migration/ram.c
>>> index 7208bc114fb5c366740db380ee6956a91b3871a0..8223183132dc0f558f45fbae3f4f832845730bd3 100644
>>> --- a/migration/ram.c
>>> +++ b/migration/ram.c
>>> @@ -3708,7 +3708,7 @@ static int ram_load_cleanup(void *opaque)
>>>    /**
>>>     * ram_postcopy_incoming_init: allocate postcopy data structures
>>>     *
>>> - * Returns 0 for success and negative if there was one error
>>> + * Returns 0 for success and -1 if there was one error
>>
>> This is true but not relevant in this patch's goal.
>>
>> Besides, I'm not in favor of letting callers make an assumption on integer
>> return values (i.e., let callers assume a particular integer value in the
>> error conditions). It is subtle to make a mistake to return -errno while the
>> documentation says it returns -1.
> 
> In general I would consider it bad practice to have an method
> with "Error **errp" that also returns an errno. 95% of the time
> the errno is just there as further info on the error scenario,
> which "errp" obsoletes. Only in the rare cases where the caller
> needs to take functional action based on errno values, is it
> appropriate to contine returning '-errno'.> > IOW, I'd consider this appropriate for the patch as is.> >> I think 
a proper way to avoid bugs due to return values here is to change
>> the type to bool, which ensures there are two possible values; that is a
>> nice improvement but something that can be done later.
> 
> That doesn't guarantee avoidance of bugs, as bool values can be
> assigned to & compared against integers.

Returning -errno with "Error **errp" is indeed a bad practice, but 
someone may write a return statement with -errno by mistake as long as 
the type is int. For callers, it is a good defensive coding practice to 
assume any negative value indicates an error as it will dismiss the 
difference of -1 or -errno, and it is what the existing documentation 
implicitly suggests.

On the other hand, a function can never have a bug to return -errno if 
its return value type is bool.

Regards,
Akihiko Odaki

Re: [PATCH v5 02/23] migration: push Error **errp into vmstate_load_state()

[Arun Menon]

Hi Daniel,

Thank you so much for the review.

On Thu, Jul 17, 2025 at 05:32:14PM +0100, Daniel P. Berrangé wrote:
> On Thu, Jul 17, 2025 at 06:07:25AM +0530, 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 <armenon@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         | 43 +++++++++++++++++++++++++++----------------
> >  tests/unit/test-vmstate.c   | 18 +++++++++---------
> >  ui/vdagent.c                |  2 +-
> >  15 files changed, 58 insertions(+), 45 deletions(-)
> > 
> 
> > diff --git a/migration/vmstate.c b/migration/vmstate.c
> > index 526668a020562f303d2ddf030b1c8466659b67be..078a00003023cc248fb16f05017d4c4251fd86df 100644
> > --- a/migration/vmstate.c
> > +++ b/migration/vmstate.c
> > @@ -132,29 +132,30 @@ 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 : %d", ret);
> 
> Suggest including
> 
>   vmsd->name, version_id, vmsd->minimum_version_id
> 
> as those are all relevant context which may aid in diagnosing
> this error.
> 
> >              return ret;
> >          }
> >      }
> > @@ -192,10 +193,12 @@ 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);
> 
> This should have the "error_setg" call, so...

About this. I saw few 'get' functions that does not have error_setg() call,
for example vhost_user_net_load_state() or get_fpscr() function calls.
I was not sure, therefore I covered both the cases.
Now I think they do satisfy the if/else if clauses.
Please correct me if I am wrong.

> 
> > @@ -211,27 +214,35 @@ 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);
> > +                    if (errp != NULL) {
> > +                        error_prepend(errp, "Failed to load %s:%s ", vmsd->name,
> > +                                      field->name);
> > +                    } else {
> > +                        error_setg(errp, "Failed to load %s:%s", vmsd->name,
> > +                                   field->name);
> > +                    }
> 
> ...this should exclusively do error_prepend.
> 
> Also include the 'version_id' here as an bit of extra context.
Yes.
> 
> >                      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",
> > +                       vmsd->name, field->name);
> 
> 
> Inlucde the version_id too
Yes.
> 
> >              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 : %d", ret);
> > +        }
> 
> Suggest including
> 
>   vmsd->name, version_id, vmsd->minimum_version_id

Agreed.
> 
> 
> >      }
> >      trace_vmstate_load_state_end(vmsd->name, "end", ret);
> >      return ret;
> 
> 
> 
> With regards,
> Daniel
> -- 
> |: https://berrange.com      -o-    https://www.flickr.com/photos/dberrange :|
> |: https://libvirt.org         -o-            https://fstop138.berrange.com :|
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> 
Regards,
Arun