Re: [Qemu-devel] [PATCH v12 2/2] migration: spapr: migrate pending_events of spapr state

[David Gibson]

On Fri, May 19, 2017 at 11:27:50AM -0300, Daniel Henrique Barboza wrote:
> From: Jianjun Duan <address@hidden>
> 
> In racing situations between hotplug events and migration operation,
> a rtas hotplug event could have not yet be delivered to the source
> guest when migration is started. In this case the pending_events of
> spapr state need be transmitted to the target so that the hotplug
> event can be finished on the target.
> 
> All the different fields of the events are encoded as defined by
> PAPR. We can migrate them as a binary stream inside VBUFFER without
> any concerns about data padding or endianess.
> 
> pending_events is put in a subsection in the spapr state VMSD to make
> sure migration across different versions is not broken.
> 
> Signed-off-by: Jianjun Duan <address@hidden>
> Signed-off-by: Daniel Henrique Barboza <address@hidden>
> ---
>  hw/ppc/spapr.c         | 32 ++++++++++++++++++++++++++++++++
>  hw/ppc/spapr_events.c  | 12 ++++++++++++
>  include/hw/ppc/spapr.h |  3 ++-
>  3 files changed, 46 insertions(+), 1 deletion(-)
> 
> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> index 0980d73..5afd328 100644
> --- a/hw/ppc/spapr.c
> +++ b/hw/ppc/spapr.c
> @@ -1444,6 +1444,37 @@ static bool version_before_3(void *opaque, int 
> version_id)
>      return version_id < 3;
>  }
>  
> +static bool spapr_pending_events_needed(void *opaque)
> +{
> +    sPAPRMachineState *spapr = (sPAPRMachineState *)opaque;
> +    return !QTAILQ_EMPTY(&spapr->pending_events);
> +}
> +
> +static const VMStateDescription vmstate_spapr_event_entry = {
> +    .name = "spapr_event_log_entry",
> +    .version_id = 1,
> +    .minimum_version_id = 1,
> +    .fields = (VMStateField[]) {
> +        VMSTATE_INT32(log_type, sPAPREventLogEntry),
> +        VMSTATE_UINT32(data_size, sPAPREventLogEntry),
> +        VMSTATE_VBUFFER_ALLOC_UINT32(data, sPAPREventLogEntry, 0,
> +                                     NULL, data_size),
> +        VMSTATE_END_OF_LIST()
> +    },
> +};
> +
> +static const VMStateDescription vmstate_spapr_pending_events = {
> +    .name = "spapr_pending_events",
> +    .version_id = 1,
> +    .minimum_version_id = 1,
> +    .needed = spapr_pending_events_needed,
> +    .fields = (VMStateField[]) {
> +        VMSTATE_QTAILQ_V(pending_events, sPAPRMachineState, 1,
> +                         vmstate_spapr_event_entry, sPAPREventLogEntry, 
> next),
> +        VMSTATE_END_OF_LIST()
> +    },
> +};
> +
>  static bool spapr_ov5_cas_needed(void *opaque)
>  {
>      sPAPRMachineState *spapr = opaque;
> @@ -1542,6 +1573,7 @@ static const VMStateDescription vmstate_spapr = {
>      .subsections = (const VMStateDescription*[]) {
>          &vmstate_spapr_ov5_cas,
>          &vmstate_spapr_patb_entry,
> +        &vmstate_spapr_pending_events,
>          NULL
>      }
>  };
> diff --git a/hw/ppc/spapr_events.c b/hw/ppc/spapr_events.c
> index 73e2a18..a509c46 100644
> --- a/hw/ppc/spapr_events.c
> +++ b/hw/ppc/spapr_events.c
> @@ -350,6 +350,18 @@ static void rtas_event_log_queue(int log_type, void 
> *data)
>      g_assert(data);
>      entry->log_type = log_type;
>      entry->data = data;
> +
> +    switch (log_type) {
> +    case RTAS_LOG_TYPE_EPOW:
> +        entry->data_size = sizeof(struct epow_log_full);
> +        break;
> +    case RTAS_LOG_TYPE_HOTPLUG:
> +        entry->data_size = sizeof(struct hp_log_full);
> +        break;
> +    default:
> +        g_assert(false);
> +    }

You can do better than this.  The header of the event has an
'extended_length' field which is set (correctly) by the existing
functions creating the events.  You'll need to add the base/common
header size back in, but that's easy.

That's how the guest determines the size of the events once they
arrive, and that's what you should use here as well.

> +
>      QTAILQ_INSERT_TAIL(&spapr->pending_events, entry, next);
>  }
>  
> diff --git a/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h
> index 02239a5..0554e11 100644
> --- a/include/hw/ppc/spapr.h
> +++ b/include/hw/ppc/spapr.h
> @@ -597,8 +597,9 @@ struct sPAPRTCETable {
>  sPAPRTCETable *spapr_tce_find_by_liobn(target_ulong liobn);
>  
>  struct sPAPREventLogEntry {
> -    int log_type;
> +    int32_t log_type;
>      void *data;
> +    uint32_t data_size;
>      QTAILQ_ENTRY(sPAPREventLogEntry) next;
>  };
>  

-- 
David Gibson                    | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au  | minimalist, thank you.  NOT _the_ _other_
                                | _way_ _around_!
http://www.ozlabs.org/~dgibson

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