[Qemu-devel] [PATCH 6/6] spapr: fix migration of ICP objects from/to older QEMU

[Greg Kurz]

Commit 5bc8d26de20c ("spapr: allocate the ICPState object from under
sPAPRCPUCore") moved ICP objects from the machine to CPU cores. This
is an improvement since we no longer allocate ICP objects that will
never be used. But it has the side-effect of breaking migration of
older machine types from older QEMU versions.

This patch introduces a compat flag in the sPAPR machine class so
that all pseries machine up to 2.9 go on with the previous behavior
of pre-allocating ICP objects.

While here, we also ensure that object_property_add_child() errors cause
QEMU to abort for newer machines.

Signed-off-by: Greg Kurz <address@hidden>
---
 hw/ppc/spapr.c          |   36 ++++++++++++++++++++++++++++++++++++
 hw/ppc/spapr_cpu_core.c |   28 ++++++++++++++++++++--------
 include/hw/ppc/spapr.h  |    2 ++
 3 files changed, 58 insertions(+), 8 deletions(-)

diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
index c53989bb10b1..ab3683bcd677 100644
--- a/hw/ppc/spapr.c
+++ b/hw/ppc/spapr.c
@@ -126,6 +126,7 @@ error:
 static void xics_system_init(MachineState *machine, int nr_irqs, Error **errp)
 {
     sPAPRMachineState *spapr = SPAPR_MACHINE(machine);
+    sPAPRMachineClass *smc = SPAPR_MACHINE_GET_CLASS(spapr);
     Error *local_err = NULL;
 
     if (kvm_enabled()) {
@@ -151,6 +152,38 @@ static void xics_system_init(MachineState *machine, int 
nr_irqs, Error **errp)
                                       &local_err);
     }
 
+    if (!spapr->ics) {
+        goto out;
+    }
+
+    if (smc->must_pre_allocate_icps) {
+        int smt = kvmppc_smt_threads();
+        int nr_servers = DIV_ROUND_UP(max_cpus * smt, smp_threads);
+        int i;
+
+        spapr->legacy_icps = g_malloc0(nr_servers * sizeof(ICPState));
+
+        for (i = 0; i < nr_servers; i++) {
+            void* obj = &spapr->legacy_icps[i];
+
+            object_initialize(obj, sizeof(ICPState), spapr->icp_type);
+            object_property_add_child(OBJECT(spapr), "icp[*]", obj,
+                                      &error_abort);
+            object_unref(obj);
+            object_property_add_const_link(obj, "xics", OBJECT(spapr),
+                                           &error_abort);
+            object_property_set_bool(obj, true, "realized", &local_err);
+            if (local_err) {
+                while (i--) {
+                    object_unparent(obj);
+                }
+                g_free(spapr->legacy_icps);
+                break;
+            }
+        }
+    }
+
+out:
     error_propagate(errp, local_err);
 }
 
@@ -3256,8 +3289,11 @@ static void 
spapr_machine_2_9_instance_options(MachineState *machine)
 
 static void spapr_machine_2_9_class_options(MachineClass *mc)
 {
+    sPAPRMachineClass *smc = SPAPR_MACHINE_CLASS(mc);
+
     spapr_machine_2_10_class_options(mc);
     SET_MACHINE_COMPAT(mc, SPAPR_COMPAT_2_9);
+    smc->must_pre_allocate_icps = true;
 }
 
 DEFINE_SPAPR_MACHINE(2_9, "2.9", false);
diff --git a/hw/ppc/spapr_cpu_core.c b/hw/ppc/spapr_cpu_core.c
index 63d160f7e010..5476647efa06 100644
--- a/hw/ppc/spapr_cpu_core.c
+++ b/hw/ppc/spapr_cpu_core.c
@@ -119,6 +119,7 @@ static void spapr_cpu_core_unrealizefn(DeviceState *dev, 
Error **errp)
     size_t size = object_type_get_instance_size(typename);
     CPUCore *cc = CPU_CORE(dev);
     int i;
+    sPAPRMachineState *spapr = SPAPR_MACHINE(qdev_get_machine());
 
     for (i = 0; i < cc->nr_threads; i++) {
         void *obj = sc->threads + i * size;
@@ -127,7 +128,9 @@ static void spapr_cpu_core_unrealizefn(DeviceState *dev, 
Error **errp)
         PowerPCCPU *cpu = POWERPC_CPU(cs);
 
         spapr_cpu_destroy(cpu);
-        object_unparent(cpu->intc);
+        if (!spapr->legacy_icps) {
+            object_unparent(cpu->intc);
+        }
         cpu_remove_sync(cs);
         object_unparent(obj);
     }
@@ -142,12 +145,19 @@ static void spapr_cpu_core_realize_child(Object *child, 
Error **errp)
     PowerPCCPU *cpu = POWERPC_CPU(cs);
     Object *obj;
 
-    obj = object_new(spapr->icp_type);
-    object_property_add_child(OBJECT(cpu), "icp", obj, NULL);
-    object_property_add_const_link(obj, "xics", OBJECT(spapr), &error_abort);
-    object_property_set_bool(obj, true, "realized", &local_err);
-    if (local_err) {
-        goto error;
+    if (spapr->legacy_icps) {
+        int index = cpu->parent_obj.cpu_index;
+
+        obj = OBJECT(&spapr->legacy_icps[index]);
+    } else {
+        obj = object_new(spapr->icp_type);
+        object_property_add_child(OBJECT(cpu), "icp", obj, &error_abort);
+        object_property_add_const_link(obj, "xics", OBJECT(spapr),
+                                       &error_abort);
+        object_property_set_bool(obj, true, "realized", &local_err);
+        if (local_err) {
+            goto error;
+        }
     }
 
     object_property_set_bool(child, true, "realized", &local_err);
@@ -164,7 +174,9 @@ static void spapr_cpu_core_realize_child(Object *child, 
Error **errp)
     return;
 
 error:
-    object_unparent(obj);
+    if (!spapr->legacy_icps) {
+        object_unparent(obj);
+    }
     error_propagate(errp, local_err);
 }
 
diff --git a/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h
index 5802f888c39d..72cd5af2679b 100644
--- a/include/hw/ppc/spapr.h
+++ b/include/hw/ppc/spapr.h
@@ -53,6 +53,7 @@ struct sPAPRMachineClass {
     bool dr_lmb_enabled;       /* enable dynamic-reconfig/hotplug of LMBs */
     bool use_ohci_by_default;  /* use USB-OHCI instead of XHCI */
     const char *tcg_default_cpu; /* which (TCG) CPU to simulate by default */
+    bool must_pre_allocate_icps; /* only for pseries-2.9 and older */
     void (*phb_placement)(sPAPRMachineState *spapr, uint32_t index,
                           uint64_t *buid, hwaddr *pio, 
                           hwaddr *mmio32, hwaddr *mmio64,
@@ -109,6 +110,7 @@ struct sPAPRMachineState {
     MemoryHotplugState hotplug_memory;
 
     const char *icp_type;
+    ICPState *legacy_icps;
 };
 
 #define H_SUCCESS         0