[PATCH v9 07/27] migration: push Error **errp into qemu_loadvm_state()

Arun Menon posted 27 patches 4 months, 1 week ago
Maintainers: Stefan Berger <stefanb@linux.vnet.ibm.com>, Peter Xu <peterx@redhat.com>, Fabiano Rosas <farosas@suse.de>, "Michael S. Tsirkin" <mst@redhat.com>, "Alex Bennée" <alex.bennee@linaro.org>, Akihiko Odaki <odaki@rsg.ci.i.u-tokyo.ac.jp>, Dmitry Osipenko <dmitry.osipenko@collabora.com>, Marcel Apfelbaum <marcel.apfelbaum@gmail.com>, Cornelia Huck <cohuck@redhat.com>, Halil Pasic <pasic@linux.ibm.com>, Eric Farman <farman@linux.ibm.com>, Richard Henderson <richard.henderson@linaro.org>, David Hildenbrand <david@redhat.com>, Ilya Leoshkevich <iii@linux.ibm.com>, Christian Borntraeger <borntraeger@linux.ibm.com>, Matthew Rosato <mjrosato@linux.ibm.com>, Thomas Huth <thuth@redhat.com>, Nicholas Piggin <npiggin@gmail.com>, Harsh Prateek Bora <harshpb@linux.ibm.com>, Paolo Bonzini <pbonzini@redhat.com>, Fam Zheng <fam@euphon.net>, Alex Williamson <alex.williamson@redhat.com>, "Cédric Le Goater" <clg@redhat.com>, Hailiang Zhang <zhanghailiang@xfusion.com>, Steve Sistare <steven.sistare@oracle.com>, "Marc-André Lureau" <marcandre.lureau@redhat.com>
There is a newer version of this series
[PATCH v9 07/27] migration: push Error **errp into qemu_loadvm_state()
Posted by Arun Menon 4 months, 1 week ago
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.

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 |  7 ++++---
 migration/savevm.c    | 31 +++++++++++++++++++------------
 migration/savevm.h    |  2 +-
 3 files changed, 24 insertions(+), 16 deletions(-)

diff --git a/migration/migration.c b/migration/migration.c
index 10c216d25dec01f206eacad2edd24d21f00e614c..bb7d5e1dee52692cbea1d2c8fdca541e6a75bedb 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;
     }
 
@@ -924,7 +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 1bd27efe437d4d911728d776e995490d0a45dcf5..ca166ebd397ad80836ed2f9cb20a92f704fd4ed5 100644
--- a/migration/savevm.c
+++ b/migration/savevm.c
@@ -3149,28 +3149,24 @@ 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, &local_err);
+    ret = qemu_loadvm_state_header(f, errp);
     if (ret) {
-        error_report_err(local_err);
         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;
     }
 
@@ -3181,6 +3177,9 @@ int qemu_loadvm_state(QEMUFile *f)
     cpu_synchronize_all_pre_loadvm();
 
     ret = qemu_loadvm_state_main(f, mis);
+    if (ret < 0) {
+        error_setg(errp, "Load VM state failed: %d", ret);
+    }
     qemu_event_set(&mis->main_thread_load_event);
 
     trace_qemu_loadvm_state_post_main(ret);
@@ -3198,8 +3197,14 @@ 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 VM state: "
+                       "Migration stream has error");
         } else {
             ret = qemu_file_get_error(f);
+            if (ret < 0) {
+                error_setg(errp, "Error while loading vmstate : %d", ret);
+            }
         }
     }
     /*
@@ -3464,6 +3469,7 @@ void qmp_xen_save_devices_state(const char *filename, bool has_live, bool live,
 
 void qmp_xen_load_devices_state(const char *filename, Error **errp)
 {
+    ERRP_GUARD();
     QEMUFile *f;
     QIOChannelFile *ioc;
     int ret;
@@ -3485,10 +3491,10 @@ 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();
 }
@@ -3496,6 +3502,7 @@ void qmp_xen_load_devices_state(const char *filename, Error **errp)
 bool load_snapshot(const char *name, const char *vmstate,
                    bool has_devices, strList *devices, Error **errp)
 {
+    ERRP_GUARD();
     BlockDriverState *bs_vm_state;
     QEMUSnapshotInfo sn;
     QEMUFile *f;
@@ -3559,13 +3566,13 @@ 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 2d5e9c716686f06720325e82fe90c75335ced1de..b80770b7461a60e2ad6ba5e24a7baeae73d90955 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);
 int qemu_load_device_state(QEMUFile *f);

-- 
2.50.1
Re: [PATCH v9 07/27] migration: push Error **errp into qemu_loadvm_state()
Posted by Akihiko Odaki 4 months, 1 week ago
On 2025/08/06 3:25, 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.
> 
> 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 |  7 ++++---
>   migration/savevm.c    | 31 +++++++++++++++++++------------
>   migration/savevm.h    |  2 +-
>   3 files changed, 24 insertions(+), 16 deletions(-)
> 
> diff --git a/migration/migration.c b/migration/migration.c
> index 10c216d25dec01f206eacad2edd24d21f00e614c..bb7d5e1dee52692cbea1d2c8fdca541e6a75bedb 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;
>       }
>   
> @@ -924,7 +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);

There is "error_report_err(s->error)" after this so this can result in 
duplicate error printing.

>   
>       migration_incoming_state_destroy();
>   
> diff --git a/migration/savevm.c b/migration/savevm.c
> index 1bd27efe437d4d911728d776e995490d0a45dcf5..ca166ebd397ad80836ed2f9cb20a92f704fd4ed5 100644
> --- a/migration/savevm.c
> +++ b/migration/savevm.c
> @@ -3149,28 +3149,24 @@ 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, &local_err);
> +    ret = qemu_loadvm_state_header(f, errp);
>       if (ret) {
> -        error_report_err(local_err);
>           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;
>       }
>   
> @@ -3181,6 +3177,9 @@ int qemu_loadvm_state(QEMUFile *f)
>       cpu_synchronize_all_pre_loadvm();
>   
>       ret = qemu_loadvm_state_main(f, mis);
> +    if (ret < 0) {
> +        error_setg(errp, "Load VM state failed: %d", ret);
> +    }
>       qemu_event_set(&mis->main_thread_load_event);
>   
>       trace_qemu_loadvm_state_post_main(ret);
> @@ -3198,8 +3197,14 @@ 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 VM state: "
> +                       "Migration stream has error");
>           } else {
>               ret = qemu_file_get_error(f);
> +            if (ret < 0) {
> +                error_setg(errp, "Error while loading vmstate : %d", ret);
> +            }
>           }
>       }
>       /*
> @@ -3464,6 +3469,7 @@ void qmp_xen_save_devices_state(const char *filename, bool has_live, bool live,
>   
>   void qmp_xen_load_devices_state(const char *filename, Error **errp)
>   {
> +    ERRP_GUARD();
>       QEMUFile *f;
>       QIOChannelFile *ioc;
>       int ret;
> @@ -3485,10 +3491,10 @@ 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();
>   }
> @@ -3496,6 +3502,7 @@ void qmp_xen_load_devices_state(const char *filename, Error **errp)
>   bool load_snapshot(const char *name, const char *vmstate,
>                      bool has_devices, strList *devices, Error **errp)
>   {
> +    ERRP_GUARD();
>       BlockDriverState *bs_vm_state;
>       QEMUSnapshotInfo sn;
>       QEMUFile *f;
> @@ -3559,13 +3566,13 @@ 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 2d5e9c716686f06720325e82fe90c75335ced1de..b80770b7461a60e2ad6ba5e24a7baeae73d90955 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);
>   int qemu_load_device_state(QEMUFile *f);
>
Re: [PATCH v9 07/27] migration: push Error **errp into qemu_loadvm_state()
Posted by Arun Menon 4 months, 1 week ago
Hi Akihiko,

Thanks for the review.

On Wed, Aug 06, 2025 at 02:17:02PM +0900, Akihiko Odaki wrote:
> On 2025/08/06 3:25, 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.
> > 
> > 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 |  7 ++++---
> >   migration/savevm.c    | 31 +++++++++++++++++++------------
> >   migration/savevm.h    |  2 +-
> >   3 files changed, 24 insertions(+), 16 deletions(-)
> > 
> > diff --git a/migration/migration.c b/migration/migration.c
> > index 10c216d25dec01f206eacad2edd24d21f00e614c..bb7d5e1dee52692cbea1d2c8fdca541e6a75bedb 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;
> >       }
> > @@ -924,7 +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);
> 
> There is "error_report_err(s->error)" after this so this can result in
> duplicate error printing.

Yes, we can replace this with error_free(s->error).

> 
> >       migration_incoming_state_destroy();
> > diff --git a/migration/savevm.c b/migration/savevm.c
> > index 1bd27efe437d4d911728d776e995490d0a45dcf5..ca166ebd397ad80836ed2f9cb20a92f704fd4ed5 100644
> > --- a/migration/savevm.c
> > +++ b/migration/savevm.c
> > @@ -3149,28 +3149,24 @@ 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, &local_err);
> > +    ret = qemu_loadvm_state_header(f, errp);
> >       if (ret) {
> > -        error_report_err(local_err);
> >           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;
> >       }
> > @@ -3181,6 +3177,9 @@ int qemu_loadvm_state(QEMUFile *f)
> >       cpu_synchronize_all_pre_loadvm();
> >       ret = qemu_loadvm_state_main(f, mis);
> > +    if (ret < 0) {
> > +        error_setg(errp, "Load VM state failed: %d", ret);
> > +    }
> >       qemu_event_set(&mis->main_thread_load_event);
> >       trace_qemu_loadvm_state_post_main(ret);
> > @@ -3198,8 +3197,14 @@ 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 VM state: "
> > +                       "Migration stream has error");
> >           } else {
> >               ret = qemu_file_get_error(f);
> > +            if (ret < 0) {
> > +                error_setg(errp, "Error while loading vmstate : %d", ret);
> > +            }
> >           }
> >       }
> >       /*
> > @@ -3464,6 +3469,7 @@ void qmp_xen_save_devices_state(const char *filename, bool has_live, bool live,
> >   void qmp_xen_load_devices_state(const char *filename, Error **errp)
> >   {
> > +    ERRP_GUARD();
> >       QEMUFile *f;
> >       QIOChannelFile *ioc;
> >       int ret;
> > @@ -3485,10 +3491,10 @@ 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();
> >   }
> > @@ -3496,6 +3502,7 @@ void qmp_xen_load_devices_state(const char *filename, Error **errp)
> >   bool load_snapshot(const char *name, const char *vmstate,
> >                      bool has_devices, strList *devices, Error **errp)
> >   {
> > +    ERRP_GUARD();
> >       BlockDriverState *bs_vm_state;
> >       QEMUSnapshotInfo sn;
> >       QEMUFile *f;
> > @@ -3559,13 +3566,13 @@ 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 2d5e9c716686f06720325e82fe90c75335ced1de..b80770b7461a60e2ad6ba5e24a7baeae73d90955 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);
> >   int qemu_load_device_state(QEMUFile *f);
> > 
> 
Regards,
Arun Menon
Re: [PATCH v9 07/27] migration: push Error **errp into qemu_loadvm_state()
Posted by Marc-André Lureau 4 months, 1 week ago
On Tue, Aug 5, 2025 at 10:28 PM Arun Menon <armenon@redhat.com> 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.
>
> 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>
>

Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>


> ---
>  migration/migration.c |  7 ++++---
>  migration/savevm.c    | 31 +++++++++++++++++++------------
>  migration/savevm.h    |  2 +-
>  3 files changed, 24 insertions(+), 16 deletions(-)
>
> diff --git a/migration/migration.c b/migration/migration.c
> index
> 10c216d25dec01f206eacad2edd24d21f00e614c..bb7d5e1dee52692cbea1d2c8fdca541e6a75bedb
> 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;
>      }
>
> @@ -924,7 +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
> 1bd27efe437d4d911728d776e995490d0a45dcf5..ca166ebd397ad80836ed2f9cb20a92f704fd4ed5
> 100644
> --- a/migration/savevm.c
> +++ b/migration/savevm.c
> @@ -3149,28 +3149,24 @@ 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, &local_err);
> +    ret = qemu_loadvm_state_header(f, errp);
>      if (ret) {
> -        error_report_err(local_err);
>          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;
>      }
>
> @@ -3181,6 +3177,9 @@ int qemu_loadvm_state(QEMUFile *f)
>      cpu_synchronize_all_pre_loadvm();
>
>      ret = qemu_loadvm_state_main(f, mis);
> +    if (ret < 0) {
> +        error_setg(errp, "Load VM state failed: %d", ret);
> +    }
>      qemu_event_set(&mis->main_thread_load_event);
>
>      trace_qemu_loadvm_state_post_main(ret);
> @@ -3198,8 +3197,14 @@ 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 VM state: "
> +                       "Migration stream has error");
>          } else {
>              ret = qemu_file_get_error(f);
> +            if (ret < 0) {
> +                error_setg(errp, "Error while loading vmstate : %d", ret);
> +            }
>          }
>      }
>      /*
> @@ -3464,6 +3469,7 @@ void qmp_xen_save_devices_state(const char
> *filename, bool has_live, bool live,
>
>  void qmp_xen_load_devices_state(const char *filename, Error **errp)
>  {
> +    ERRP_GUARD();
>      QEMUFile *f;
>      QIOChannelFile *ioc;
>      int ret;
> @@ -3485,10 +3491,10 @@ 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();
>  }
> @@ -3496,6 +3502,7 @@ void qmp_xen_load_devices_state(const char
> *filename, Error **errp)
>  bool load_snapshot(const char *name, const char *vmstate,
>                     bool has_devices, strList *devices, Error **errp)
>  {
> +    ERRP_GUARD();
>      BlockDriverState *bs_vm_state;
>      QEMUSnapshotInfo sn;
>      QEMUFile *f;
> @@ -3559,13 +3566,13 @@ 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
> 2d5e9c716686f06720325e82fe90c75335ced1de..b80770b7461a60e2ad6ba5e24a7baeae73d90955
> 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);
>  int qemu_load_device_state(QEMUFile *f);
>
> --
> 2.50.1
>
>