[Qemu-devel] [QEMU RFC PATCH v2 2/6] Migration: Defined VMStateDescription struct for spapr_drc

[Jianjun Duan]

To manage hotplug/unplug of dynamic resources such as PCI cards,
memory, and CPU on sPAPR guests, a firmware abstraction known as
a Dynamic Resource Connector (DRC) is used to assign a particular
dynamic resource to the guest, and provide an interface for the
guest to manage configuration/removal of the resource associated
with it.

To migrate the hotplugged resources in migration, the
associated DRC state need be migrated. To migrate the DRC state,
we defined the VMStateDescription struct for spapr_drc to enable
the transmission of spapr_drc state in migration.

Not all the elements in the DRC state are migrated. Only those
ones modifiable or needed by guest actions or device add/remove
operation are migrated. From the perspective of device
hotplugging, if we hotplug a device on the source, we need to
"coldplug" it on the target. The states across two hosts for the
same device are not the same. Ideally we want the states be same
after migration so that the device would function as hotplugged
on the target. For example we can unplug it. The minimum DRC
state we need to transfer should cover all the pieces changed by
hotplugging. Out of the elements of the DRC state, isolation_state,
allocation_sate, and configured are involved in the DR state
transition diagram from PAPR+ 2.7, 13.4. configured and signalled
are needed in attaching and detaching devices. indicator_state
provides users with hardware state information. These 6 elements
are migrated.

detach_cb in the DRC state is a function pointer that cannot be
migrated. We set it right after DRC state is migrated so that
a migrated hot-unplug event could finish its work.

Signed-off-by: Jianjun Duan <address@hidden>
---
 hw/ppc/spapr_drc.c         | 61 ++++++++++++++++++++++++++++++++++++++++++++++
 hw/ppc/spapr_pci.c         | 22 +++++++++++++++++
 include/hw/ppc/spapr_drc.h |  9 +++++++
 3 files changed, 92 insertions(+)

diff --git a/hw/ppc/spapr_drc.c b/hw/ppc/spapr_drc.c
index 94c875d..1fb5e23 100644
--- a/hw/ppc/spapr_drc.c
+++ b/hw/ppc/spapr_drc.c
@@ -617,6 +617,65 @@ static void spapr_dr_connector_instance_init(Object *obj)
                         NULL, NULL, NULL, NULL);
 }
 
+static bool spapr_drc_needed(void *opaque)
+{
+    sPAPRDRConnector *drc = (sPAPRDRConnector *)opaque;
+    sPAPRDRConnectorClass *drck = SPAPR_DR_CONNECTOR_GET_CLASS(drc);
+    bool rc = false;
+    sPAPRDREntitySense value;
+
+    drck->entity_sense(drc, &value);
+    /* If no dev is plugged in there is no need to migrate the DRC state */
+    if (value != SPAPR_DR_ENTITY_SENSE_PRESENT) {
+        return false;
+    }
+    /*
+     * If there is dev plugged in, we need to migrate the DRC state when
+     * it is different from cold-plugged state
+     */
+    switch(drc->type) {
+    /* for PCI type */
+    case SPAPR_DR_CONNECTOR_TYPE_PCI:
+        rc = !((drc->isolation_state == SPAPR_DR_ISOLATION_STATE_UNISOLATED) &&
+               (drc->allocation_state == SPAPR_DR_ALLOCATION_STATE_USABLE) &&
+               drc->configured && drc->signalled && !drc->awaiting_release);
+        break;
+    /* for LMB type */
+    case SPAPR_DR_CONNECTOR_TYPE_LMB:
+        rc = !((drc->isolation_state == SPAPR_DR_ISOLATION_STATE_ISOLATED) &&
+               (drc->allocation_state == SPAPR_DR_ALLOCATION_STATE_UNUSABLE) &&
+               drc->configured && drc->signalled && !drc->awaiting_release);
+        break;
+    default:
+        ;
+    }
+
+    return rc;
+}
+
+/* detach_cb needs be set since it is not migrated */
+static void postmigrate_set_detach_cb(sPAPRDRConnector *drc,
+                                      spapr_drc_detach_cb *detach_cb)
+{
+    drc->detach_cb = detach_cb;
+}
+
+static const VMStateDescription vmstate_spapr_drc = {
+    .name = "spapr_drc",
+    .version_id = 1,
+    .minimum_version_id = 1,
+    .needed = spapr_drc_needed,
+    .fields  = (VMStateField []) {
+        VMSTATE_UINT32(isolation_state, sPAPRDRConnector),
+        VMSTATE_UINT32(allocation_state, sPAPRDRConnector),
+        VMSTATE_UINT32(indicator_state, sPAPRDRConnector),
+        VMSTATE_BOOL(configured, sPAPRDRConnector),
+        VMSTATE_BOOL(awaiting_release, sPAPRDRConnector),
+        VMSTATE_BOOL(signalled, sPAPRDRConnector),
+        VMSTATE_END_OF_LIST()
+    }
+};
+
 static void spapr_dr_connector_class_init(ObjectClass *k, void *data)
 {
     DeviceClass *dk = DEVICE_CLASS(k);
@@ -625,6 +684,7 @@ static void spapr_dr_connector_class_init(ObjectClass *k, 
void *data)
     dk->reset = reset;
     dk->realize = realize;
     dk->unrealize = unrealize;
+    dk->vmsd = &vmstate_spapr_drc;
     drck->set_isolation_state = set_isolation_state;
     drck->set_indicator_state = set_indicator_state;
     drck->set_allocation_state = set_allocation_state;
@@ -638,6 +698,7 @@ static void spapr_dr_connector_class_init(ObjectClass *k, 
void *data)
     drck->detach = detach;
     drck->release_pending = release_pending;
     drck->set_signalled = set_signalled;
+    drck->postmigrate_set_detach_cb = postmigrate_set_detach_cb;
     /*
      * Reason: it crashes FIXME find and document the real reason
      */
diff --git a/hw/ppc/spapr_pci.c b/hw/ppc/spapr_pci.c
index f0b9de9..e10774d 100644
--- a/hw/ppc/spapr_pci.c
+++ b/hw/ppc/spapr_pci.c
@@ -1561,11 +1561,33 @@ static void spapr_pci_pre_save(void *opaque)
     }
 }
 
+/*
+ * detach_cb in the DRC state is a function pointer that cannot be
+ * migrated. We set it right after migration so that a migrated
+ * hot-unplug event could finish its work.
+ */
+static void spapr_pci_set_detach_cb(PCIBus *bus, PCIDevice *pdev,
+                                 void *opaque)
+{
+    sPAPRPHBState *sphb = opaque;
+    sPAPRDRConnector *drc = spapr_phb_get_pci_drc(sphb, pdev);
+    sPAPRDRConnectorClass *drck = SPAPR_DR_CONNECTOR_GET_CLASS(drc);
+    drck->postmigrate_set_detach_cb(drc, spapr_phb_remove_pci_device_cb);
+}
+
 static int spapr_pci_post_load(void *opaque, int version_id)
 {
     sPAPRPHBState *sphb = opaque;
     gpointer key, value;
     int i;
+    PCIBus *bus = PCI_HOST_BRIDGE(sphb)->bus;
+    unsigned int bus_no = 0;
+
+    /* Set detach_cb for the drc unconditionally after migration */
+    if (bus) {
+        pci_for_each_device(bus, pci_bus_num(bus), spapr_pci_set_detach_cb,
+                            &bus_no);
+    }
 
     for (i = 0; i < sphb->msi_devs_num; ++i) {
         key = g_memdup(&sphb->msi_devs[i].key,
diff --git a/include/hw/ppc/spapr_drc.h b/include/hw/ppc/spapr_drc.h
index fa21ba0..a68433b 100644
--- a/include/hw/ppc/spapr_drc.h
+++ b/include/hw/ppc/spapr_drc.h
@@ -190,6 +190,15 @@ typedef struct sPAPRDRConnectorClass {
                    void *detach_cb_opaque, Error **errp);
     bool (*release_pending)(sPAPRDRConnector *drc);
     void (*set_signalled)(sPAPRDRConnector *drc);
+
+    /*
+     * QEMU interface for setting detach_cb after migration.
+     * detach_cb in the DRC state is a function pointer that cannot be
+     * migrated. We set it right after migration so that a migrated
+     * hot-unplug event could finish its work.
+     */
+    void (*postmigrate_set_detach_cb)(sPAPRDRConnector *drc,
+                                      spapr_drc_detach_cb *detach_cb);
 } sPAPRDRConnectorClass;
 
 sPAPRDRConnector *spapr_dr_connector_new(Object *owner,
-- 
1.9.1