Re: [PATCH v6 4/9] vfio/migration: Add an Error** argument to vfio_migration_set_state()

[Cédric Le Goater]

On 5/15/24 09:20, Eric Auger wrote:
> Hi Cédric,
>
> On 5/14/24 17:31, Cédric Le Goater wrote:
> > Add an Error** argument to vfio_migration_set_state() and adjust
> > callers, including vfio_save_setup(). The error will be propagated up
> > to qemu_savevm_state_setup() where the save_setup() handler is
> > executed.
> >
> > Modify vfio_vmstate_change_prepare() and vfio_vmstate_change() to
> > store a reported error under the migration stream if a migration is in
> > progress.
> >
> > Signed-off-by: Cédric Le Goater <clg@redhat.com>
> > ---
> >
> >   Changes in v6:
> >
> >   - Commit log improvements (Avihai)
> >   - vfio_migration_set_state() : Dropped the error_setg_errno() change
> >     when setting device in recover state fails (Avihai)
> >   - vfio_migration_state_notifier() : report local error (Avihai)
> >     
> >   Changes in v5:
> >
> >   - Replaced error_setg() by error_setg_errno() in vfio_migration_set_state()
> >   - Rebased on 20c64c8a51a4 ("migration: migration_file_set_error")
> >   
> >   hw/vfio/migration.c | 77 ++++++++++++++++++++++++++++-----------------
> >   1 file changed, 48 insertions(+), 29 deletions(-)
> >
> > diff --git a/hw/vfio/migration.c b/hw/vfio/migration.c
> > index 
> > bf2fd0759ba6e4fb103cc5c1a43edb180a3d0de4..bf11135167ebb162dd41415656bdacfa0e1ca550
> >  100644
> > --- a/hw/vfio/migration.c
> > +++ b/hw/vfio/migration.c
> > @@ -82,7 +82,8 @@ static const char *mig_state_to_str(enum 
> > vfio_device_mig_state state)
> >   
> >   static int vfio_migration_set_state(VFIODevice *vbasedev,
> >                                       enum vfio_device_mig_state new_state,
> > -                                    enum vfio_device_mig_state recover_state)
> > +                                    enum vfio_device_mig_state recover_state,
> > +                                    Error **errp)
> >   {
> >       VFIOMigration *migration = vbasedev->migration;
> >       uint64_t buf[DIV_ROUND_UP(sizeof(struct vfio_device_feature) +
> > @@ -102,18 +103,19 @@ static int vfio_migration_set_state(VFIODevice *vbasedev,
> >           ret = -errno;
> >   
> >           if (recover_state == VFIO_DEVICE_STATE_ERROR) {
> > -            error_report("%s: Failed setting device state to %s, err: %s. "
> > -                         "Recover state is ERROR. Resetting device",
> > -                         vbasedev->name, mig_state_to_str(new_state),
> > -                         strerror(errno));
> > +            error_setg_errno(errp, errno,
> > +                             "%s: Failed setting device state to %s. "
> > +                             "Recover state is ERROR. Resetting device",
> > +                             vbasedev->name, mig_state_to_str(new_state));
> nit: this may be simplified
> with a first unconditional msg saying Failed setting device state to %s.
> Recover state is %s.
> and not duplicating the msg.
>
> In the reset label you can prepend "resetting the device ..."

I agree.

I'd rather do that in a followup patch after ther error_setg_* changes.
Adding to the TODO list.

> >   
> >               goto reset_device;
> >           }
> >   
> > -        error_report(
> > -            "%s: Failed setting device state to %s, err: %s. Setting device in 
> > recover state %s",
> > -                     vbasedev->name, mig_state_to_str(new_state),
> > -                     strerror(errno), mig_state_to_str(recover_state));
> > +        error_setg_errno(errp, errno,
> > +                         "%s: Failed setting device state to %s. "
> > +                         "Setting device in recover state %s",
> > +                         vbasedev->name, mig_state_to_str(new_state),
> > +                         mig_state_to_str(recover_state));>
> >           mig_state->device_state = recover_state;
> >           if (ioctl(vbasedev->fd, VFIO_DEVICE_FEATURE, feature)) {
> in case you fail setting the device in recover state, your simply
> error_report() and do not prepend any other msg in the error handle. Is
> it what you want? 

yes. Otherwise, we loose the previous error message, which I think is more
important to report (first error). The following error_report handles an
error of an error, which can go on stderr.

> In the positive, maybe worth a comment.

OK, to avoid a resend, I will amend the patch with:

         mig_state->device_state = recover_state;
         if (ioctl(vbasedev->fd, VFIO_DEVICE_FEATURE, feature)) {
             ret = -errno;
+            /*
+             * If setting the device in recover state fails, report
+             * the error here and propagate the first error.
+             */
             error_report(
                 "%s: Failed setting device in recover state, err: %s. Resetting 
device",
                          vbasedev->name, strerror(errno));


Thanks,

C.




> > @@ -137,7 +139,7 @@ static int vfio_migration_set_state(VFIODevice *vbasedev,
> >                * This can happen if the device is asynchronously reset and
> >                * terminates a data transfer.
> >                */
> > -            error_report("%s: data_fd out of sync", vbasedev->name);
> > +            error_setg(errp, "%s: data_fd out of sync", vbasedev->name);
> >               close(mig_state->data_fd);
> >   
> >               return -EBADF;
> > @@ -168,10 +170,11 @@ reset_device:
> >    */
> >   static int
> >   vfio_migration_set_state_or_reset(VFIODevice *vbasedev,
> > -                                  enum vfio_device_mig_state new_state)
> > +                                  enum vfio_device_mig_state new_state,
> > +                                  Error **errp)
> >   {
> >       return vfio_migration_set_state(vbasedev, new_state,
> > -                                    VFIO_DEVICE_STATE_ERROR);
> > +                                    VFIO_DEVICE_STATE_ERROR, errp);
> >   }
> >   
> >   static int vfio_load_buffer(QEMUFile *f, VFIODevice *vbasedev,
> > @@ -399,10 +402,8 @@ static int vfio_save_setup(QEMUFile *f, void *opaque, 
> > Error **errp)
> >           switch (migration->device_state) {
> >           case VFIO_DEVICE_STATE_RUNNING:
> >               ret = vfio_migration_set_state(vbasedev, 
> > VFIO_DEVICE_STATE_PRE_COPY,
> > -                                           VFIO_DEVICE_STATE_RUNNING);
> > +                                           VFIO_DEVICE_STATE_RUNNING, errp);
> >               if (ret) {
> > -                error_setg(errp, "%s: Failed to set new PRE_COPY state",
> > -                           vbasedev->name);
> >                   return ret;
> >               }
> >   
> > @@ -435,13 +436,20 @@ static void vfio_save_cleanup(void *opaque)
> >   {
> >       VFIODevice *vbasedev = opaque;
> >       VFIOMigration *migration = vbasedev->migration;
> > +    Error *local_err = NULL;
> > +    int ret;
> >   
> >       /*
> >        * Changing device state from STOP_COPY to STOP can take time. Do it here,
> >        * after migration has completed, so it won't increase downtime.
> >        */
> >       if (migration->device_state == VFIO_DEVICE_STATE_STOP_COPY) {
> > -        vfio_migration_set_state_or_reset(vbasedev, VFIO_DEVICE_STATE_STOP);
> > +        ret = vfio_migration_set_state_or_reset(vbasedev,
> > +                                                VFIO_DEVICE_STATE_STOP,
> > +                                                &local_err);
> > +        if (ret) {
> > +            error_report_err(local_err);
> > +        }
> >       }
> >   
> >       g_free(migration->data_buffer);
> > @@ -549,11 +557,13 @@ static int vfio_save_complete_precopy(QEMUFile *f, void 
> > *opaque)
> >       VFIODevice *vbasedev = opaque;
> >       ssize_t data_size;
> >       int ret;
> > +    Error *local_err = NULL;
> >   
> >       /* We reach here with device state STOP or STOP_COPY only */
> >       ret = vfio_migration_set_state(vbasedev, VFIO_DEVICE_STATE_STOP_COPY,
> > -                                   VFIO_DEVICE_STATE_STOP);
> > +                                   VFIO_DEVICE_STATE_STOP, &local_err);
> >       if (ret) {
> > +        error_report_err(local_err);
> >           return ret;
> >       }
> >   
> > @@ -591,14 +601,9 @@ static void vfio_save_state(QEMUFile *f, void *opaque)
> >   static int vfio_load_setup(QEMUFile *f, void *opaque, Error **errp)
> >   {
> >       VFIODevice *vbasedev = opaque;
> > -    int ret;
> >   
> > -    ret = vfio_migration_set_state(vbasedev, VFIO_DEVICE_STATE_RESUMING,
> > -                                   vbasedev->migration->device_state);
> > -    if (ret) {
> > -        error_setg(errp, "%s: Failed to set RESUMING state", vbasedev->name);
> > -    }
> > -    return ret;
> > +    return vfio_migration_set_state(vbasedev, VFIO_DEVICE_STATE_RESUMING,
> > +                                    vbasedev->migration->device_state, errp);
> >   }
> >   
> >   static int vfio_load_cleanup(void *opaque)
> > @@ -714,19 +719,20 @@ static void vfio_vmstate_change_prepare(void *opaque, 
> > bool running,
> >       VFIODevice *vbasedev = opaque;
> >       VFIOMigration *migration = vbasedev->migration;
> >       enum vfio_device_mig_state new_state;
> > +    Error *local_err = NULL;
> >       int ret;
> >   
> >       new_state = migration->device_state == VFIO_DEVICE_STATE_PRE_COPY ?
> >                       VFIO_DEVICE_STATE_PRE_COPY_P2P :
> >                       VFIO_DEVICE_STATE_RUNNING_P2P;
> >   
> > -    ret = vfio_migration_set_state_or_reset(vbasedev, new_state);
> > +    ret = vfio_migration_set_state_or_reset(vbasedev, new_state, &local_err);
> >       if (ret) {
> >           /*
> >            * Migration should be aborted in this case, but vm_state_notify()
> >            * currently does not support reporting failures.
> >            */
> > -        migration_file_set_error(ret, NULL);
> > +        migration_file_set_error(ret, local_err);
> >       }
> >   
> >       trace_vfio_vmstate_change_prepare(vbasedev->name, running,
> > @@ -738,6 +744,7 @@ static void vfio_vmstate_change(void *opaque, bool running, 
> > RunState state)
> >   {
> >       VFIODevice *vbasedev = opaque;
> >       enum vfio_device_mig_state new_state;
> > +    Error *local_err = NULL;
> >       int ret;
> >   
> >       if (running) {
> > @@ -750,13 +757,13 @@ static void vfio_vmstate_change(void *opaque, bool 
> > running, RunState state)
> >                   VFIO_DEVICE_STATE_STOP;
> >       }
> >   
> > -    ret = vfio_migration_set_state_or_reset(vbasedev, new_state);
> > +    ret = vfio_migration_set_state_or_reset(vbasedev, new_state, &local_err);
> >       if (ret) {
> >           /*
> >            * Migration should be aborted in this case, but vm_state_notify()
> >            * currently does not support reporting failures.
> >            */
> > -        migration_file_set_error(ret, NULL);
> > +        migration_file_set_error(ret, local_err);
> >       }
> >   
> >       trace_vfio_vmstate_change(vbasedev->name, running, RunState_str(state),
> > @@ -769,11 +776,23 @@ static int 
> > vfio_migration_state_notifier(NotifierWithReturn *notifier,
> >       VFIOMigration *migration = container_of(notifier, VFIOMigration,
> >                                               migration_state);
> >       VFIODevice *vbasedev = migration->vbasedev;
> > +    Error *local_err = NULL;
> > +    int ret = 0;
> >   
> >       trace_vfio_migration_state_notifier(vbasedev->name, e->type);
> >   
> >       if (e->type == MIG_EVENT_PRECOPY_FAILED) {
> > -        vfio_migration_set_state_or_reset(vbasedev, VFIO_DEVICE_STATE_RUNNING);
> > +        /*
> > +         * MigrationNotifyFunc may return an error code and an Error
> > +         * object only for MIG_EVENT_PRECOPY_SETUP. Hence, report the
> > +         * error locally and ignore the errp argument.
> > +         */
> > +        ret = vfio_migration_set_state_or_reset(vbasedev,
> > +                                                VFIO_DEVICE_STATE_RUNNING,
> > +                                                &local_err);
> > +        if (ret) {
> > +            error_report_err(local_err);
> > +        }
> >       }
> >       return 0;
> >   }
> Thanks
>
> Eric