[Qemu-devel] [PATCH v3 4/6] numa: introduce "numa-mem-supported" machine property

[Igor Mammedov <imammedo@redhat.com>]

'-numa mem' option has a number of issues and mgmt often defaults
to it. Unfortunately it's no possible to replace it with an alternative
'-numa memdev' without breaking migration compatibility. What's possible
though is to deprecate it, keeping option working with old machine types.
Once deprecation period expires, QEMU will disable '-numa mem' option,
usage on new machine types and when the last machine type that supported
it is removed we would be able to remove '-numa mem' with associated code.

In order to help mgmt to find out if being deprecated CLI option
'-numa mem=SZ' is still supported by particular machine type, expose
this information via "numa-mem-supported" machine property.

Users can use "qom-list-properties" QMP command to list machine type
properties including initial proprety values (when probing for supported
machine types with '-machine none') or at runtime at preconfig time
before numa mapping is configured and decide if they should used legacy
'-numa mem' or alternative '-numa memdev' option.

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
---
 include/hw/boards.h |  1 +
 hw/arm/virt.c       |  1 +
 hw/core/machine.c   | 12 ++++++++++++
 hw/i386/pc.c        |  1 +
 hw/ppc/spapr.c      |  1 +
 5 files changed, 16 insertions(+)

diff --git a/include/hw/boards.h b/include/hw/boards.h
index 6f7916f..9e347cf 100644
--- a/include/hw/boards.h
+++ b/include/hw/boards.h
@@ -210,6 +210,7 @@ struct MachineClass {
     bool ignore_boot_device_suffixes;
     bool smbus_no_migration_support;
     bool nvdimm_supported;
+    bool numa_mem_supported;
 
     HotplugHandler *(*get_hotplug_handler)(MachineState *machine,
                                            DeviceState *dev);
diff --git a/hw/arm/virt.c b/hw/arm/virt.c
index 5331ab7..2e86c78 100644
--- a/hw/arm/virt.c
+++ b/hw/arm/virt.c
@@ -1943,6 +1943,7 @@ static void virt_machine_class_init(ObjectClass *oc, void *data)
     assert(!mc->get_hotplug_handler);
     mc->get_hotplug_handler = virt_machine_get_hotplug_handler;
     hc->plug = virt_machine_device_plug_cb;
+    mc->numa_mem_supported = true;
 }
 
 static void virt_instance_init(Object *obj)
diff --git a/hw/core/machine.c b/hw/core/machine.c
index 5d046a4..8bc53ba 100644
--- a/hw/core/machine.c
+++ b/hw/core/machine.c
@@ -506,6 +506,13 @@ static char *machine_get_nvdimm_persistence(Object *obj, Error **errp)
     return g_strdup(ms->nvdimms_state->persistence_string);
 }
 
+static bool machine_get_numa_mem_supported(Object *obj, Error **errp)
+{
+    MachineClass *mc = MACHINE_GET_CLASS(obj);
+
+    return mc->numa_mem_supported;
+}
+
 static void machine_set_nvdimm_persistence(Object *obj, const char *value,
                                            Error **errp)
 {
@@ -810,6 +817,11 @@ static void machine_class_init(ObjectClass *oc, void *data)
         &error_abort);
     object_class_property_set_description(oc, "memory-encryption",
         "Set memory encryption object to use", &error_abort);
+
+    object_class_property_add_bool(oc, "numa-mem-supported",
+        machine_get_numa_mem_supported, NULL, &error_abort);
+    object_class_property_set_description(oc, "numa-mem-supported",
+        "Shows if legacy '-numa mem=SIZE option is supported", &error_abort);
 }
 
 static void machine_class_base_init(ObjectClass *oc, void *data)
diff --git a/hw/i386/pc.c b/hw/i386/pc.c
index de91e90..bec0055 100644
--- a/hw/i386/pc.c
+++ b/hw/i386/pc.c
@@ -2756,6 +2756,7 @@ static void pc_machine_class_init(ObjectClass *oc, void *data)
     nc->nmi_monitor_handler = x86_nmi;
     mc->default_cpu_type = TARGET_DEFAULT_CPU_TYPE;
     mc->nvdimm_supported = true;
+    mc->numa_mem_supported = true;
 
     object_class_property_add(oc, PC_MACHINE_DEVMEM_REGION_SIZE, "int",
         pc_machine_get_device_memory_region_size, NULL,
diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
index 2ef3ce4..265ecfb 100644
--- a/hw/ppc/spapr.c
+++ b/hw/ppc/spapr.c
@@ -4336,6 +4336,7 @@ static void spapr_machine_class_init(ObjectClass *oc, void *data)
      * in which LMBs are represented and hot-added
      */
     mc->numa_mem_align_shift = 28;
+    mc->numa_mem_supported = true;
 
     smc->default_caps.caps[SPAPR_CAP_HTM] = SPAPR_CAP_OFF;
     smc->default_caps.caps[SPAPR_CAP_VSX] = SPAPR_CAP_ON;
-- 
2.7.4