Arun Menon <[email protected]> writes:
> Hi Fabiano,
>
> Thanks for the review.
>
> On Fri, Aug 15, 2025 at 12:41:50PM -0300, Fabiano Rosas wrote:
>> Arun Menon <[email protected]> writes:
>>
>> > 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.
>> >
>> > Reviewed-by: Marc-André Lureau <[email protected]>
>> > Signed-off-by: Arun Menon <[email protected]>
>> > ---
>> > hw/display/virtio-gpu.c | 2 +-
>> > hw/pci/pci.c | 3 ++-
>> > hw/s390x/virtio-ccw.c | 2 +-
>> > hw/scsi/spapr_vscsi.c | 2 +-
>> > hw/vfio/pci.c | 3 ++-
>> > hw/virtio/virtio-mmio.c | 3 ++-
>> > hw/virtio/virtio-pci.c | 2 +-
>> > hw/virtio/virtio.c | 4 +--
>> > include/migration/vmstate.h | 2 +-
>> > migration/cpr.c | 5 ++--
>> > migration/savevm.c | 6 +++--
>> > migration/vmstate-types.c | 22 ++++++++++++----
>> > migration/vmstate.c | 61
>> > ++++++++++++++++++++++++++++++-------------
>> > tests/unit/test-vmstate.c | 63
>> > ++++++++++++++++++++++++++++++++++++++-------
>> > ui/vdagent.c | 3 ++-
>> > 15 files changed, 136 insertions(+), 47 deletions(-)
>> >
>> > diff --git a/hw/display/virtio-gpu.c b/hw/display/virtio-gpu.c
>> > index
>> > 0a1a625b0ea6cf26cb0d799171a57ed3d3ab2442..5dc31bc6bfb0272e29a4364ab10de2595a4bedf7
>> > 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,
>> > &error_fatal);
>> >
>> > return 0;
>> > }
>> > diff --git a/hw/pci/pci.c b/hw/pci/pci.c
>> > index
>> > c70b5ceebaf1f2b10768bd030526cbb518da2b8d..6be932d3bb67ff0c4808707db2a7b6378a90e82b
>> > 100644
>> > --- a/hw/pci/pci.c
>> > +++ b/hw/pci/pci.c
>> > @@ -934,7 +934,8 @@ 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,
>> > + &error_fatal);
>> > /* 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..6a9641a03d5d3a38a4de7ceb9deffc0cc303bcff
>> > 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,
>> > &error_fatal);
>> > }
>> >
>> > 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..8c896022d324f51962605288d6d6df1648c83cde
>> > 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,
>> > &error_fatal);
>> > 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
>> > 4fa692c1a32bcfa4e4939e5fcb64f2bf19905b3b..0be54762cdcbdb4780b8228b0bdf7fc6bd74dd57
>> > 100644
>> > --- a/hw/vfio/pci.c
>> > +++ b/hw/vfio/pci.c
>> > @@ -2795,7 +2795,8 @@ 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,
>> > + &error_fatal);
>> > if (ret) {
>> > return ret;
>> > }
>> > diff --git a/hw/virtio/virtio-mmio.c b/hw/virtio/virtio-mmio.c
>> > index
>> > 532c67107ba1d2978a76cf49f9cdc1de1dea3e11..0a688909fc606a3c9fde933667ae8c309ab527d0
>> > 100644
>> > --- a/hw/virtio/virtio-mmio.c
>> > +++ b/hw/virtio/virtio-mmio.c
>> > @@ -34,6 +34,7 @@
>> > #include "qemu/error-report.h"
>> > #include "qemu/log.h"
>> > #include "trace.h"
>> > +#include "qapi/error.h"
>> >
>> > static bool virtio_mmio_ioeventfd_enabled(DeviceState *d)
>> > {
>> > @@ -619,7 +620,7 @@ 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,
>> > &error_fatal);
>> > }
>> >
>> > 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..b04faa1e5c91b5cef40e54ec41d92422d16bfc13
>> > 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,
>> > &error_fatal);
>> > }
>> >
>> > 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
>> > 9a81ad912e013fc254899c4e55cff1f76a6112a4..6bcafb338d1b5becadcacf092ba33a6ae4c3d194
>> > 100644
>> > --- a/hw/virtio/virtio.c
>> > +++ b/hw/virtio/virtio.c
>> > @@ -3327,14 +3327,14 @@ 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,
>> > &error_fatal);
>> > if (ret) {
>> > return ret;
>> > }
>> > }
>> >
>> > /* Subsections */
>> > - ret = vmstate_load_state(f, &vmstate_virtio, vdev, 1);
>> > + ret = vmstate_load_state(f, &vmstate_virtio, vdev, 1, &error_fatal);
>> > 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..bdb24736f44e91ba59b6e622a315597c97e7f64d
>> > 100644
>> > --- a/migration/cpr.c
>> > +++ b/migration/cpr.c
>> > @@ -202,6 +202,7 @@ int cpr_state_save(MigrationChannel *channel, Error
>> > **errp)
>> >
>> > int cpr_state_load(MigrationChannel *channel, Error **errp)
>> > {
>> > + ERRP_GUARD();
>> > int ret;
>> > uint32_t v;
>> > QEMUFile *f;
>> > @@ -233,9 +234,9 @@ 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..cb64f2855d46aaa7c617b3e4079a2c9e566079b2
>> > 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,
>> > + &error_fatal);
>> > }
>> >
>> > 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,
>> > + &error_fatal);
>> >
>> > if (ret) {
>> > return ret;
>> > diff --git a/migration/vmstate-types.c b/migration/vmstate-types.c
>> > index
>> > 741a588b7e18c6d37724b08a0101edc8bc74a0a5..f41670cc853c5b41ccc8def354886a8e5c1451fd
>> > 100644
>> > --- a/migration/vmstate-types.c
>> > +++ b/migration/vmstate-types.c
>> > @@ -19,6 +19,7 @@
>> > #include "qemu/error-report.h"
>> > #include "qemu/queue.h"
>> > #include "trace.h"
>> > +#include "qapi/error.h"
>> >
>> > /* bool */
>> >
>> > @@ -543,13 +544,17 @@ static int get_tmp(QEMUFile *f, void *pv, size_t
>> > size,
>> > const VMStateField *field)
>> > {
>> > int ret;
>> > + Error *local_err = NULL;
>> > const VMStateDescription *vmsd = field->vmsd;
>> > int version_id = field->version_id;
>> > void *tmp = g_malloc(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, &local_err);
>> > + if (ret < 0) {
>> > + warn_report_err(local_err);
>> > + }
>> > g_free(tmp);
>> > return ret;
>> > }
>> > @@ -626,6 +631,7 @@ static int get_qtailq(QEMUFile *f, void *pv, size_t
>> > unused_size,
>> > const VMStateField *field)
>> > {
>> > int ret = 0;
>> > + Error *local_err = NULL;
>> > const VMStateDescription *vmsd = field->vmsd;
>> > /* size of a QTAILQ element */
>> > size_t size = field->size;
>> > @@ -649,8 +655,9 @@ 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, &local_err);
>> > if (ret) {
>> > + warn_report_err(local_err);
>> > return ret;
>> > }
>> > QTAILQ_RAW_INSERT_TAIL(pv, elm, entry_offset);
>> > @@ -772,6 +779,7 @@ static int get_gtree(QEMUFile *f, void *pv, size_t
>> > unused_size,
>> > GTree *tree = *pval;
>> > void *key, *val;
>> > int ret = 0;
>> > + Error *local_err = NULL;
>> >
>> > /* in case of direct key, the key vmsd can be {}, ie. check fields */
>> > if (!direct_key && version_id > key_vmsd->version_id) {
>> > @@ -803,18 +811,20 @@ 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,
>> > &local_err);
>> > if (ret) {
>> > error_report("%s : failed to load %s (%d)",
>> > field->name, key_vmsd->name, ret);
>> > + warn_report_err(local_err);
>> > goto key_error;
>> > }
>> > }
>> > 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,
>> > &local_err);
>> > if (ret) {
>> > error_report("%s : failed to load %s (%d)",
>> > field->name, val_vmsd->name, ret);
>> > + warn_report_err(local_err);
>> > goto val_error;
>> > }
>> > g_tree_insert(tree, key, val);
>> > @@ -872,6 +882,7 @@ static int get_qlist(QEMUFile *f, void *pv, size_t
>> > unused_size,
>> > const VMStateField *field)
>> > {
>> > int ret = 0;
>> > + Error *local_err = NULL;
>> > const VMStateDescription *vmsd = field->vmsd;
>> > /* size of a QLIST element */
>> > size_t size = field->size;
>> > @@ -892,10 +903,11 @@ 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, &local_err);
>> > if (ret) {
>> > error_report("%s: failed to load %s (%d)", field->name,
>> > vmsd->name, ret);
>> > + warn_report_err(local_err);
>> > g_free(elm);
>> > return ret;
>> > }
>> > diff --git a/migration/vmstate.c b/migration/vmstate.c
>> > index
>> > 6108c7fe283a5013ce42ea9987723c489aef26a2..1cd609a1d598995af1e51d1f4d58d68133f1426d
>> > 100644
>> > --- a/migration/vmstate.c
>> > +++ b/migration/vmstate.c
>> > @@ -132,29 +132,34 @@ 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)
>> > {
>> > + ERRP_GUARD();
>> > const VMStateField *field = vmsd->fields;
>> > int ret = 0;
>> >
>> > trace_vmstate_load_state(vmsd->name, version_id);
>> > if (version_id > vmsd->version_id) {
>> > - error_report("%s: incoming version_id %d is too new "
>> > - "for local version_id %d",
>> > - vmsd->name, version_id, vmsd->version_id);
>> > + error_setg(errp, "%s: incoming version_id %d is too new "
>> > + "for local version_id %d",
>> > + vmsd->name, version_id, vmsd->version_id);
>> > trace_vmstate_load_state_end(vmsd->name, "too new", -EINVAL);
>> > return -EINVAL;
>> > }
>> > if (version_id < vmsd->minimum_version_id) {
>> > - error_report("%s: incoming version_id %d is too old "
>> > - "for local minimum version_id %d",
>> > - vmsd->name, version_id, vmsd->minimum_version_id);
>> > + error_setg(errp, "%s: incoming version_id %d is too old "
>> > + "for local minimum version_id %d",
>> > + vmsd->name, version_id, vmsd->minimum_version_id);
>> > trace_vmstate_load_state_end(vmsd->name, "too old", -EINVAL);
>> > return -EINVAL;
>> > }
>> > if (vmsd->pre_load) {
>> > ret = vmsd->pre_load(opaque);
>> > if (ret) {
>> > + error_setg(errp, "VM pre load failed for: '%s', "
>>
>> "VM" pre load is a little ambiguous. Simply "pre load" or "pre load
>> hook" is better.
> Sure, will do this.
>>
>> > + "version_id: %d, minimum version_id: %d, ret: %d",
>> > + vmsd->name, vmsd->version_id,
>> > vmsd->minimum_version_id,
>> > + ret);
>> > return ret;
>> > }
>> > }
>> > @@ -192,13 +197,20 @@ 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);
>> > + if (ret < 0) {
>> > + error_setg(errp,
>> > + "Failed to get info for %s: %d",
>> > + inner_field->name, ret);
>>
>> "get info" is not correct. This is the type-specific getter
>> invocation. Because the migration (for the most part) is a stream, each
>> type provides it's own getter which knows about the size of the field
>> and any particularities such as magic values. So:
>>
>> error_setg(errp, "Failed to load element of type %s for %s: %d",
>> info->name, inner_field->name, ret);
> yes, will change the message. Thanks.
>>
>> > + }
>> > }
>> >
>> > /* If we used a fake temp field.. free it now */
>> > @@ -208,30 +220,42 @@ int vmstate_load_state(QEMUFile *f, const
>> > VMStateDescription *vmsd,
>> >
>> > if (ret >= 0) {
>> > ret = qemu_file_get_error(f);
>> > + if (ret < 0) {
>> > + error_setg(errp, "Failed to load %s state: %d",
>> > + vmsd->name, ret);
>>
>> We could go a little more specific here, it's useful to know whether the
>> error was on the transport side, rather than something logical with the
>> migrated data. I don't really care about the actual string, but one
>> suggestion is "stream error":
>>
>> error_setg(errp, "Failed to load %s state: stream error: %d",
>> vmsd->name, ret);
> yes, will add stream error. Thanks.
>>
>> > + }
>> > }
>> > if (ret < 0) {
>> > qemu_file_set_error(f, ret);
>> > - error_report("Failed to load %s:%s", vmsd->name,
>> > - field->name);
>> > + error_prepend(errp,
>> > + "Failed to load %s:%s version_id: %d: ",
>>
>> Usage of : is inconsistent with below /
> Since we used error_prepend here, we need an extra space after the colon ':'
> That way the next error string looks readable.
Right, that's not what I'm talking about. What's inconsistent is: %s:%s
vs. %s/%s
>>
>> > + vmsd->name, field->name,
>> > vmsd->version_id);
>> > trace_vmstate_load_field_error(field->name, ret);
>> > return ret;
>> > }
>> > }
>> > } else if (field->flags & VMS_MUST_EXIST) {
>> > - error_report("Input validation failed: %s/%s",
>> > - vmsd->name, field->name);
>> > + error_setg(errp, "Input validation failed: %s/%s version_id:
>> > %d",
here^
