Re: [Qemu-devel] [Qemu-ppc] [PATCH v9 6/6] migration: spapr: migrate pending_events of spapr state

[Daniel Henrique Barboza]

On 05/12/2017 03:28 AM, David Gibson wrote:
> On Fri, May 05, 2017 at 05:47:46PM -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 uint8_t binary stream 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>
> This seems like it's probably a good idea, even independent of the
> hotplug migration stuff.  I suspect there are other races where we
> could lose a shutdown event or similar if there's a migration.
Perhaps we can detach this patch (and the ccs_list one) from this
series and evaluate them separately?


Daniel

> > ---
> >   hw/ppc/spapr.c         | 33 +++++++++++++++++++++++++++++++++
> >   hw/ppc/spapr_events.c  | 24 +++++++++++++-----------
> >   include/hw/ppc/spapr.h |  3 ++-
> >   3 files changed, 48 insertions(+), 12 deletions(-)
> >
> > diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> > index bc56249..e924fd4 100644
> > --- a/hw/ppc/spapr.c
> > +++ b/hw/ppc/spapr.c
> > @@ -1498,6 +1498,38 @@ static const VMStateDescription vmstate_spapr_ccs_list = 
> > {
> >       },
> >   };
> >   
> > +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),
> This requires changing the actual type to int32_t in the structure.
>
> > +        VMSTATE_BOOL(exception, sPAPREventLogEntry),
> So, at the moment, AFAICT every event is marked as exception == true,
> so this doesn't actually tell us anything.   If that becomes not the
> case in future, can the exception flag be derived from the log_type or
> information in the even buffer?
>
> > +        VMSTATE_UINT32(data_size, sPAPREventLogEntry),
> > +        VMSTATE_VARRAY_UINT32_ALLOC(data, sPAPREventLogEntry, data_size,
> > +                                    0, vmstate_info_uint8, uint8_t),
> So, data_size duplicates information that's in the event header, which
> is a bit sad.  I suppose I'm ok with that, since setting up the VARRAY
> thing is going to be pretty awkward otherwise.
>
> > +        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;
> > @@ -1598,6 +1630,7 @@ static const VMStateDescription vmstate_spapr = {
> >           &vmstate_spapr_patb_entry,
> >           &vmstate_spapr_pending_dimm_unplugs,
> >           &vmstate_spapr_ccs_list,
> > +        &vmstate_spapr_pending_events,
> >           NULL
> >       }
> >   };
> > diff --git a/hw/ppc/spapr_events.c b/hw/ppc/spapr_events.c
> > index f0b28d8..70c7cfc 100644
> > --- a/hw/ppc/spapr_events.c
> > +++ b/hw/ppc/spapr_events.c
> > @@ -342,7 +342,8 @@ static int rtas_event_log_to_irq(sPAPRMachineState *spapr, 
> > int log_type)
> >       return source->irq;
> >   }
> >   
> > -static void rtas_event_log_queue(int log_type, void *data, bool exception)
> > +static void rtas_event_log_queue(int log_type, void *data, bool exception,
> > +                                 int data_size)
> >   {
> >       sPAPRMachineState *spapr = SPAPR_MACHINE(qdev_get_machine());
> >       sPAPREventLogEntry *entry = g_new(sPAPREventLogEntry, 1);
> > @@ -351,6 +352,7 @@ static void rtas_event_log_queue(int log_type, void *data, 
> > bool exception)
> >       entry->log_type = log_type;
> >       entry->exception = exception;
> >       entry->data = data;
> > +    entry->data_size = data_size;
> I think it would make more sense to derive data_size from the buffer
> header contents here, rather than in all the callers.
>
> >       QTAILQ_INSERT_TAIL(&spapr->pending_events, entry, next);
> >   }
> >   
> > @@ -445,6 +447,7 @@ static void spapr_powerdown_req(Notifier *n, void *opaque)
> >       struct rtas_event_log_v6_mainb *mainb;
> >       struct rtas_event_log_v6_epow *epow;
> >       struct epow_log_full *new_epow;
> > +    uint32_t data_size;
> >   
> >       new_epow = g_malloc0(sizeof(*new_epow));
> >       hdr = &new_epow->hdr;
> > @@ -453,14 +456,13 @@ static void spapr_powerdown_req(Notifier *n, void *opaque)
> >       mainb = &new_epow->mainb;
> >       epow = &new_epow->epow;
> >   
> > +    data_size = sizeof(*new_epow);
> >       hdr->summary = cpu_to_be32(RTAS_LOG_VERSION_6
> >                                  | RTAS_LOG_SEVERITY_EVENT
> >                                  | RTAS_LOG_DISPOSITION_NOT_RECOVERED
> >                                  | RTAS_LOG_OPTIONAL_PART_PRESENT
> >                                  | RTAS_LOG_TYPE_EPOW);
> > -    hdr->extended_length = cpu_to_be32(sizeof(*new_epow)
> > -                                       - sizeof(new_epow->hdr));
> > -
> > +    hdr->extended_length = cpu_to_be32(data_size - sizeof(new_epow->hdr));
> >       spapr_init_v6hdr(v6hdr);
> >       spapr_init_maina(maina, 3 /* Main-A, Main-B and EPOW */);
> >   
> > @@ -479,7 +481,7 @@ static void spapr_powerdown_req(Notifier *n, void *opaque)
> >       epow->event_modifier = RTAS_LOG_V6_EPOW_MODIFIER_NORMAL;
> >       epow->extended_modifier = RTAS_LOG_V6_EPOW_XMODIFIER_PARTITION_SPECIFIC;
> >   
> > -    rtas_event_log_queue(RTAS_LOG_TYPE_EPOW, new_epow, true);
> > +    rtas_event_log_queue(RTAS_LOG_TYPE_EPOW, new_epow, true, data_size);
> >   
> >       qemu_irq_pulse(xics_get_qirq(XICS_FABRIC(spapr),
> >                                    rtas_event_log_to_irq(spapr,
> > @@ -504,6 +506,7 @@ static void spapr_hotplug_req_event(uint8_t hp_id, uint8_t 
> > hp_action,
> >       struct rtas_event_log_v6_maina *maina;
> >       struct rtas_event_log_v6_mainb *mainb;
> >       struct rtas_event_log_v6_hp *hp;
> > +    uint32_t data_size;
> >   
> >       new_hp = g_malloc0(sizeof(struct hp_log_full));
> >       hdr = &new_hp->hdr;
> > @@ -512,14 +515,14 @@ static void spapr_hotplug_req_event(uint8_t hp_id, 
> > uint8_t hp_action,
> >       mainb = &new_hp->mainb;
> >       hp = &new_hp->hp;
> >   
> > +    data_size = sizeof(*new_hp);
> >       hdr->summary = cpu_to_be32(RTAS_LOG_VERSION_6
> >                                  | RTAS_LOG_SEVERITY_EVENT
> >                                  | RTAS_LOG_DISPOSITION_NOT_RECOVERED
> >                                  | RTAS_LOG_OPTIONAL_PART_PRESENT
> >                                  | RTAS_LOG_INITIATOR_HOTPLUG
> >                                  | RTAS_LOG_TYPE_HOTPLUG);
> > -    hdr->extended_length = cpu_to_be32(sizeof(*new_hp)
> > -                                       - sizeof(new_hp->hdr));
> > +    hdr->extended_length = cpu_to_be32(data_size - sizeof(new_hp->hdr));
> >   
> >       spapr_init_v6hdr(v6hdr);
> >       spapr_init_maina(maina, 3 /* Main-A, Main-B, HP */);
> > @@ -572,7 +575,7 @@ static void spapr_hotplug_req_event(uint8_t hp_id, uint8_t 
> > hp_action,
> >               cpu_to_be32(drc_id->count_indexed.index);
> >       }
> >   
> > -    rtas_event_log_queue(RTAS_LOG_TYPE_HOTPLUG, new_hp, true);
> > +    rtas_event_log_queue(RTAS_LOG_TYPE_HOTPLUG, new_hp, true, data_size);
> >   
> >       qemu_irq_pulse(xics_get_qirq(XICS_FABRIC(spapr),
> >                                    rtas_event_log_to_irq(spapr,
> > @@ -671,8 +674,7 @@ static void check_exception(PowerPCCPU *cpu, 
> > sPAPRMachineState *spapr,
> >       if (!event) {
> >           goto out_no_events;
> >       }
> > -
> > -    hdr = event->data;
> > +    hdr = (struct rtas_error_log *)event->data;
> >       event_len = be32_to_cpu(hdr->extended_length) + sizeof(*hdr);
> >   
> >       if (event_len < len) {
> > @@ -728,7 +730,7 @@ static void event_scan(PowerPCCPU *cpu, sPAPRMachineState 
> > *spapr,
> >           goto out_no_events;
> >       }
> >   
> > -    hdr = event->data;
> > +    hdr = (struct rtas_error_log *)event->data;
> >       event_len = be32_to_cpu(hdr->extended_length) + sizeof(*hdr);
> >   
> >       if (event_len < len) {
> > diff --git a/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h
> > index adc9fdb..ddac014 100644
> > --- a/include/hw/ppc/spapr.h
> > +++ b/include/hw/ppc/spapr.h
> > @@ -603,7 +603,8 @@ sPAPRTCETable *spapr_tce_find_by_liobn(target_ulong liobn);
> >   struct sPAPREventLogEntry {
> >       int log_type;
> >       bool exception;
> > -    void *data;
> > +    uint8_t *data;
> I think you can avoid this type change (and the casts it requires) by
> using VBUFFER instead of VARRAY.
>
> > +    uint32_t data_size;
> >       QTAILQ_ENTRY(sPAPREventLogEntry) next;
> >   };
> >