Hi Akihiko,
Thanks for the review.
On Fri, Aug 01, 2025 at 04:12:34PM +0900, Akihiko Odaki wrote:
> On 2025/07/31 22:20, 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 <arme...@redhat.com>
> > ---
> > migration/savevm.c | 36 ++++++++++++++++++++----------------
> > 1 file changed, 20 insertions(+), 16 deletions(-)
> >
> > diff --git a/migration/savevm.c b/migration/savevm.c
> > index
> > 736410be867a29efa24d749528c9bc203a3e8131..59751677c1bb7c893b4ba61cbfe1f55ade6ad598
> > 100644
> > --- a/migration/savevm.c
> > +++ b/migration/savevm.c
> > @@ -2690,8 +2690,9 @@ 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)
> > {
> > + ERRP_GUARD();
> > bool trace_downtime = (type == QEMU_VM_SECTION_FULL);
> > uint32_t instance_id, version_id, section_id;
> > int64_t start_ts, end_ts;
> > @@ -2702,8 +2703,8 @@ 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);
> > @@ -2711,8 +2712,7 @@ 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, "Failed to read instance/version ID: %d", ret);
> > return ret;
> > }
> > @@ -2721,17 +2721,17 @@ 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;
> > @@ -2739,7 +2739,7 @@ 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;
> > }
> > @@ -2747,10 +2747,11 @@ 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;
> > }
> > @@ -2761,6 +2762,9 @@ qemu_loadvm_section_start_full(QEMUFile *f, uint8_t
> > type)
> > }
> > if (!check_section_footer(f, se)) {
> > + error_setg(errp, "Reading footer section of instance "
> > + "0x%"PRIx32" of device '%s' for version_id:'%d' failed",
> > + instance_id, idstr, version_id);
> > return -EINVAL;
> > }
> > @@ -3063,7 +3067,7 @@ 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);
>
> The converted error_report() calls are temporarily dismissed. This can be
> fixed by moving "[PATCH v8 19/27] migration: push Error **errp into
> qemu_loadvm_state_main()" and changes for its caller earlier than this.
>
> qemu_loadvm_state_main() can have some code to fill errp until all the
> functions its calls get converted. It will not make the patch bigger thanks
> to the unified error handling path with "goto out" and the removal of code
> changes to replace NULL with errp.
I see your point.
There is a cyclic dependency between few functions.
For example, qemu_loadvm_state_main() calls -> loadvm_process_command()
calls -> loadvm_handle_cmd_packaged()
calls -> qemu_loadvm_state_main()
That is why I passed NULL temporarily and then change that in the subsequent
patches. However, I see that this will cause problems for reviewing and
bisection.
I can introduce a local_err in the caller, and when errp is available, I can
pass that.
That way I will be reporting local_err after it returns. That way the individual
patches will report the error.
>
> > if (ret < 0) {
> > goto out;
> > }
> >
>
Regards,
Arun
