Re: [Qemu-devel] [Qemu-ppc] [PATCH v11 2/2] migration: spapr: migrate pending_events of spapr state

[Daniel Henrique Barboza]

On 05/18/2017 11:32 PM, David Gibson wrote:
On Thu, May 18, 2017 at 05:24:02PM -0300, Daniel Henrique Barboza wrote:
From: Jianjun Duan <du...@linux.vnet.ibm.com>

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 <du...@linux.vnet.ibm.com>
Signed-off-by: Daniel Henrique Barboza <danie...@linux.vnet.ibm.com>
---
  hw/ppc/spapr.c         | 32 ++++++++++++++++++++++++++++++++
  hw/ppc/spapr_events.c  |  1 +
  include/hw/ppc/spapr.h |  3 ++-
  3 files changed, 35 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..96c1605 100644
--- a/hw/ppc/spapr_events.c
+++ b/hw/ppc/spapr_events.c
@@ -350,6 +350,7 @@ static void rtas_event_log_queue(int log_type, void *data)
      g_assert(data);
      entry->log_type = log_type;
      entry->data = data;
+    entry->data_size = sizeof(*data);
This can't be right, since data is a void*.  I'm surprised it even
compiles.  You'll need to actually look into the data buffer here and
extract the size field.
Hehe completely forgot here that I was querying the sizeof void. Good catch.
I think it didn't throw an error because the compiler defaulted the type 
of void
in sizeof() to something else (char perhaps?).

I'll fix it by making a switch with the log_type and setting sizeof with 
the proper
structured used.


Daniel

      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;
  };