[Qemu-devel] [PULL 5/5] spapr: disintricate core-id from DT semantics

[David Gibson <david@gibson.dropbear.id.au>]

From: Greg Kurz <groug@kaod.org>

The goal of this patch is to have a stable core-id which does not depend
on any DT related semantics, which involve non-obvious computations on
modern PowerPC server cpus.

With this patch, the DT core id is computed on-demand as:

       (core-id / smp_threads) * smt

where smt is the number of threads per core in the host.

This formula should be consolidated in a helper since it is needed in
several places.

Other uses for core-id includes: compute a stable cpu_index (which
allows random order hotplug/unplug without breaking migration) and
NUMA.

Signed-off-by: Greg Kurz <groug@kaod.org>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
---
 hw/ppc/spapr.c          | 10 +++++-----
 hw/ppc/spapr_cpu_core.c | 24 +++++++++++-------------
 2 files changed, 16 insertions(+), 18 deletions(-)

diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
index 9193ac2..fbbd051 100644
--- a/hw/ppc/spapr.c
+++ b/hw/ppc/spapr.c
@@ -1815,10 +1815,11 @@ static void ppc_spapr_init(MachineState *machine)
 
         spapr->cores = g_new0(Object *, spapr_max_cores);
         for (i = 0; i < spapr_max_cores; i++) {
-            int core_dt_id = i * smt;
+            int core_id = i * smp_threads;
             sPAPRDRConnector *drc =
                 spapr_dr_connector_new(OBJECT(spapr),
-                                       SPAPR_DR_CONNECTOR_TYPE_CPU, core_dt_id);
+                                       SPAPR_DR_CONNECTOR_TYPE_CPU,
+                                       (core_id / smp_threads) * smt);
 
             qemu_register_reset(spapr_drc_reset, drc);
 
@@ -1834,7 +1835,7 @@ static void ppc_spapr_init(MachineState *machine)
                 core  = object_new(type);
                 object_property_set_int(core, smp_threads, "nr-threads",
                                         &error_fatal);
-                object_property_set_int(core, core_dt_id, CPU_CORE_PROP_CORE_ID,
+                object_property_set_int(core, core_id, CPU_CORE_PROP_CORE_ID,
                                         &error_fatal);
                 object_property_set_bool(core, true, "realized", &error_fatal);
             }
@@ -2376,7 +2377,6 @@ static HotpluggableCPUList *spapr_query_hotpluggable_cpus(MachineState *machine)
     HotpluggableCPUList *head = NULL;
     sPAPRMachineState *spapr = SPAPR_MACHINE(machine);
     int spapr_max_cores = max_cpus / smp_threads;
-    int smt = kvmppc_smt_threads();
 
     for (i = 0; i < spapr_max_cores; i++) {
         HotpluggableCPUList *list_item = g_new0(typeof(*list_item), 1);
@@ -2386,7 +2386,7 @@ static HotpluggableCPUList *spapr_query_hotpluggable_cpus(MachineState *machine)
         cpu_item->type = spapr_get_cpu_core_type(machine->cpu_model);
         cpu_item->vcpus_count = smp_threads;
         cpu_props->has_core_id = true;
-        cpu_props->core_id = i * smt;
+        cpu_props->core_id = i * smp_threads;
         /* TODO: add 'has_node/node' here to describe
            to which node core belongs */
 
diff --git a/hw/ppc/spapr_cpu_core.c b/hw/ppc/spapr_cpu_core.c
index 4bfc96b..c04aaa4 100644
--- a/hw/ppc/spapr_cpu_core.c
+++ b/hw/ppc/spapr_cpu_core.c
@@ -103,7 +103,6 @@ static void spapr_core_release(DeviceState *dev, void *opaque)
     size_t size = object_type_get_instance_size(typename);
     sPAPRMachineState *spapr = SPAPR_MACHINE(qdev_get_machine());
     CPUCore *cc = CPU_CORE(dev);
-    int smt = kvmppc_smt_threads();
     int i;
 
     for (i = 0; i < cc->nr_threads; i++) {
@@ -117,7 +116,7 @@ static void spapr_core_release(DeviceState *dev, void *opaque)
         object_unparent(obj);
     }
 
-    spapr->cores[cc->core_id / smt] = NULL;
+    spapr->cores[cc->core_id / smp_threads] = NULL;
 
     g_free(sc->threads);
     object_unparent(OBJECT(dev));
@@ -128,18 +127,19 @@ void spapr_core_unplug(HotplugHandler *hotplug_dev, DeviceState *dev,
 {
     sPAPRMachineState *spapr = SPAPR_MACHINE(OBJECT(hotplug_dev));
     CPUCore *cc = CPU_CORE(dev);
+    int smt = kvmppc_smt_threads();
+    int index = cc->core_id / smp_threads;
     sPAPRDRConnector *drc =
-        spapr_dr_connector_by_id(SPAPR_DR_CONNECTOR_TYPE_CPU, cc->core_id);
+        spapr_dr_connector_by_id(SPAPR_DR_CONNECTOR_TYPE_CPU, index * smt);
     sPAPRDRConnectorClass *drck;
     Error *local_err = NULL;
-    int smt = kvmppc_smt_threads();
-    int index = cc->core_id / smt;
     int spapr_max_cores = max_cpus / smp_threads;
     int i;
 
     for (i = spapr_max_cores - 1; i > index; i--) {
         if (spapr->cores[i]) {
-            error_setg(errp, "core-id %d should be removed first", i * smt);
+            error_setg(errp, "core-id %d should be removed first",
+                       i * smp_threads);
             return;
         }
     }
@@ -168,11 +168,10 @@ void spapr_core_plug(HotplugHandler *hotplug_dev, DeviceState *dev,
     Error *local_err = NULL;
     void *fdt = NULL;
     int fdt_offset = 0;
-    int index;
+    int index = cc->core_id / smp_threads;
     int smt = kvmppc_smt_threads();
 
-    drc = spapr_dr_connector_by_id(SPAPR_DR_CONNECTOR_TYPE_CPU, cc->core_id);
-    index = cc->core_id / smt;
+    drc = spapr_dr_connector_by_id(SPAPR_DR_CONNECTOR_TYPE_CPU, index * smt);
     spapr->cores[index] = OBJECT(dev);
 
     if (!smc->dr_cpu_enabled) {
@@ -226,7 +225,6 @@ void spapr_core_pre_plug(HotplugHandler *hotplug_dev, DeviceState *dev,
     sPAPRMachineState *spapr = SPAPR_MACHINE(OBJECT(hotplug_dev));
     int spapr_max_cores = max_cpus / smp_threads;
     int index, i;
-    int smt = kvmppc_smt_threads();
     Error *local_err = NULL;
     CPUCore *cc = CPU_CORE(dev);
     char *base_core_type = spapr_get_cpu_core_type(machine->cpu_model);
@@ -247,12 +245,12 @@ void spapr_core_pre_plug(HotplugHandler *hotplug_dev, DeviceState *dev,
         goto out;
     }
 
-    if (cc->core_id % smt) {
+    if (cc->core_id % smp_threads) {
         error_setg(&local_err, "invalid core id %d\n", cc->core_id);
         goto out;
     }
 
-    index = cc->core_id / smt;
+    index = cc->core_id / smp_threads;
     if (index < 0 || index >= spapr_max_cores) {
         error_setg(&local_err, "core id %d out of range", cc->core_id);
         goto out;
@@ -266,7 +264,7 @@ void spapr_core_pre_plug(HotplugHandler *hotplug_dev, DeviceState *dev,
     for (i = 0; i < index; i++) {
         if (!spapr->cores[i]) {
             error_setg(&local_err, "core-id %d should be added first",
-                       i * smt);
+                       i * smp_threads);
             goto out;
         }
     }
-- 
2.7.4