Igor Mammedov <imammedo(a)redhat.com&gt; writes: Reproduced: $ qemu-system-x86_64 -nodefaults -S -display none -preconfig -qmp stdio {"QMP": {"version": {"qemu": {"micro": 50, "minor": 0, "major": 4}, "package": "v4.0.0-828-ga7b21f6762"}, "capabilities": ["oob"]}} {"execute": "qmp_capabilities"} {"return": {}} {"execute": "qom-get", "arguments": {"path": "/machine", "property": "device-memory-region-size"}} Segmentation fault (core dumped) First time I started looking at this series, I went "I'll need a reproducer to fully understand what's up, and I don't feel like finding one now; next series, please". Second time, I had to spend a few minutes on the reproducer. Wasn't hard, since you provided a clue. Still: make review easy, include a reproducer whenever you can. This makes qom-get return 0 for the size of memory that doesn't exist, yet. A possible alternative would be setting an error. Opinions?

Add in the command output object's property values right after creation (i.e. state of the object returned by object_new() or equivalent). Follow up patch will add machine property 'numa-mem-supported', which would allow mgmt to introspect which machine types (versions) still support legacy "-numa mem=FOO" CLI option and which don't and require alternative '-numa memdev' option being used. Signed-off-by: Igor Mammedov <imammedo(a)redhat.com&gt; --- qapi/misc.json | 5 ++++- qmp.c | 5 +++++ 2 files changed, 9 insertions(+), 1 deletion(-) diff --git a/qapi/misc.json b/qapi/misc.json index 8b3ca4f..e333285 100644 --- a/qapi/misc.json +++ b/qapi/misc.json @@ -1365,10 +1365,13 @@ # # @description: if specified, the description of the property. # +# @default: initial property value. +# # Since: 1.2 ## { 'struct': 'ObjectPropertyInfo', - 'data': { 'name': 'str', 'type': 'str', '*description': 'str' } } + 'data': { 'name': 'str', 'type': 'str', '*description': 'str', + '*default': 'any' } } ## # @qom-list: diff --git a/qmp.c b/qmp.c index b92d62c..8415541 100644 --- a/qmp.c +++ b/qmp.c @@ -593,6 +593,11 @@ ObjectPropertyInfoList *qmp_qom_list_properties(const char *typename, info->type = g_strdup(prop->type); info->has_description = !!prop->description; info->description = g_strdup(prop->description); + if (obj) { + info->q_default = + object_property_get_qobject(obj, info->name, NULL); + info->has_q_default = !!info->q_default; + } entry = g_malloc0(sizeof(*entry)); entry->value = info; -- 2.7.4

Current QAPI semantics return empty "" string in case string property value hasn't been set (i.e. NULL). Do not show initial value in this case in "qom-list-properties" command output to reduce clutter. Signed-off-by: Igor Mammedov <imammedo(a)redhat.com&gt; --- qmp.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) diff --git a/qmp.c b/qmp.c index 8415541..463c7d4 100644 --- a/qmp.c +++ b/qmp.c @@ -41,6 +41,7 @@ #include "qom/object_interfaces.h" #include "hw/mem/memory-device.h" #include "hw/acpi/acpi_dev_interface.h" +#include "qapi/qmp/qstring.h" NameInfo *qmp_query_name(Error **errp) { @@ -596,7 +597,16 @@ ObjectPropertyInfoList *qmp_qom_list_properties(const char *typename, if (obj) { info->q_default = object_property_get_qobject(obj, info->name, NULL); - info->has_q_default = !!info->q_default; + if (info->q_default) { + if (qobject_type(info->q_default) == QTYPE_QSTRING) { + QString *value = qobject_to(QString, info->q_default); + if (!strcmp(qstring_get_str(value), "")) { + qobject_unref(info->q_default); + info->q_default = NULL; + } + } + info->has_q_default = !!info->q_default; + } } entry = g_malloc0(sizeof(*entry)); -- 2.7.4

'-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(a)redhat.com&gt; --- 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

The parameter allows to configure fake NUMA topology where guest VM simulates NUMA topology but not actually getting a performance benefits from it. The same or better results could be achieved using 'memdev' parameter. In light of that any VM that uses NUMA to get its benefits should use 'memdev'. To allow transition initial RAM to device based model, deprecate 'mem' parameter as its ad-hoc partitioning of initial RAM MemoryRegion can't be translated to memdev based backend transparently to users and in compatible manner (migration wise). That will also allow to clean up a bit our numa code, leaving only 'memdev' impl. in place and several boards that use node_mem to generate FDT/ACPI description from it. Signed-off-by: Igor Mammedov <imammedo(a)redhat.com&gt; --- v3: * mention "numa-mem-supported" machine property in deprecation documentation. --- numa.c | 2 ++ qemu-deprecated.texi | 16 ++++++++++++++++ 2 files changed, 18 insertions(+) diff --git a/numa.c b/numa.c index 3875e1e..2205773 100644 --- a/numa.c +++ b/numa.c @@ -121,6 +121,8 @@ static void parse_numa_node(MachineState *ms, NumaNodeOptions *node, if (node->has_mem) { numa_info[nodenr].node_mem = node->mem; + warn_report("Parameter -numa node,mem is deprecated," + " use -numa node,memdev instead"); } if (node->has_memdev) { Object *o; diff --git a/qemu-deprecated.texi b/qemu-deprecated.texi index 842e71b..995a96c 100644 --- a/qemu-deprecated.texi +++ b/qemu-deprecated.texi @@ -72,6 +72,22 @@ backend settings instead of environment variables. To ease migration to the new format, the ``-audiodev-help'' option can be used to convert the current values of the environment variables to ``-audiodev'' options. +@subsection -numa node,mem=@var{size} (since 4.1) + +The parameter @option{mem} of @option{-numa node} is used to assign a part of +guest RAM to a NUMA node. But when using it, it's impossible to manage specified +size on the host side (like bind it to a host node, setting bind policy, ...), +so guest end-ups with the fake NUMA configuration with suboptiomal performance. +However since 2014 there is an alternative way to assign RAM to a NUMA node +using parameter @option{memdev}, which does the same as @option{mem} and provides +means to actualy manage node RAM on the host side. Use parameter @option{memdev} +with @var{memory-backend-ram} backend as an replacement for parameter @option{mem} +to achieve the same fake NUMA effect or a properly configured +@var{memory-backend-file} backend to actually benefit from NUMA configuration. +In future new machine versions will not accept the option but it will keep +working with old machine types. User can inspect read-only machine property +'numa-mem-supported' to check if specific machine type (not) supports the option. + @section QEMU Machine Protocol (QMP) commands @subsection block-dirty-bitmap-add "autoload" parameter (since 2.12.0) -- 2.7.4