qmp: add QMP interface "query-cpu-model-expansion"

Let's provide a standardized interface to expand CPU models. This interface
can be used by tooling to get details about a specific CPU model in a
certain configuration, e.g. about the "host" model.

To take care of all architectures, two detail levels for an expansion
are introduced. Certain architectures might not support all detail levels.
While "full" will expand and indicate all relevant properties/features
of a CPU model, "static" expands to a static base CPU model, that will
never change between QEMU versions and therefore have the same features
when used under different compatibility machines.

Acked-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Reviewed-by: Eduardo Habkost <ehabkost@redhat.com>
Signed-off-by: David Hildenbrand <dahi@linux.vnet.ibm.com>
Message-Id: <20160905085244.99980-26-dahi@linux.vnet.ibm.com>
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>

include/sysemu/arch_init.h

@@ -35,5 +35,8 @@ int kvm_available(void);
 int xen_available(void);
 
 CpuDefinitionInfoList *arch_query_cpu_definitions(Error **errp);
+CpuModelExpansionInfo *arch_query_cpu_model_expansion(CpuModelExpansionType type,
+                                                      CpuModelInfo *mode,
+                                                      Error **errp);
 
 #endif

qapi-schema.json

@@ -3066,6 +3066,98 @@
 ##
 { 'command': 'query-cpu-definitions', 'returns': ['CpuDefinitionInfo'] }
 
+##
+# @CpuModelInfo:
+#
+# Virtual CPU model.
+#
+# A CPU model consists of the name of a CPU definition, to which
+# delta changes are applied (e.g. features added/removed). Most magic values
+# that an architecture might require should be hidden behind the name.
+# However, if required, architectures can expose relevant properties.
+#
+# @name: the name of the CPU definition the model is based on
+# @props: #optional a dictionary of QOM properties to be applied
+#
+# Since: 2.8.0
+##
+{ 'struct': 'CpuModelInfo',
+  'data': { 'name': 'str',
+            '*props': 'any' } }
+
+##
+# @CpuModelExpansionType
+#
+# An enumeration of CPU model expansion types.
+#
+# @static: Expand to a static CPU model, a combination of a static base
+#          model name and property delta changes. As the static base model will
+#          never change, the expanded CPU model will be the same, independant of
+#          independent of QEMU version, machine type, machine options, and
+#          accelerator options. Therefore, the resulting model can be used by
+#          tooling without having to specify a compatibility machine - e.g. when
+#          displaying the "host" model. static CPU models are migration-safe.
+#
+# @full: Expand all properties. The produced model is not guaranteed to be
+#        migration-safe, but allows tooling to get an insight and work with
+#        model details.
+#
+# Since: 2.8.0
+##
+{ 'enum': 'CpuModelExpansionType',
+  'data': [ 'static', 'full' ] }
+
+
+##
+# @CpuModelExpansionInfo
+#
+# The result of a cpu model expansion.
+#
+# @model: the expanded CpuModelInfo.
+#
+# Since: 2.8.0
+##
+{ 'struct': 'CpuModelExpansionInfo',
+  'data': { 'model': 'CpuModelInfo' } }
+
+
+##
+# @query-cpu-model-expansion:
+#
+# Expands a given CPU model (or a combination of CPU model + additional options)
+# to different granularities, allowing tooling to get an understanding what a
+# specific CPU model looks like in QEMU under a certain configuration.
+#
+# This interface can be used to query the "host" CPU model.
+#
+# The data returned by this command may be affected by:
+#
+# * QEMU version: CPU models may look different depending on the QEMU version.
+#   (Except for CPU models reported as "static" in query-cpu-definitions.)
+# * machine-type: CPU model  may look different depending on the machine-type.
+#   (Except for CPU models reported as "static" in query-cpu-definitions.)
+# * machine options (including accelerator): in some architectures, CPU models
+#   may look different depending on machine and accelerator options. (Except for
+#   CPU models reported as "static" in query-cpu-definitions.)
+# * "-cpu" arguments and global properties: arguments to the -cpu option and
+#   global properties may affect expansion of CPU models. Using
+#   query-cpu-model-expansion while using these is not advised.
+#
+# Some architectures may not support all expansion types.
+#
+# Returns: a CpuModelExpansionInfo. Returns an error if expanding CPU models is
+#          not supported, if the model cannot be expanded, if the model contains
+#          an unknown CPU definition name, unknown properties or properties
+#          with a wrong type. Also returns an error if an expansion type is
+#          not supported.
+#
+# Since: 2.8.0
+##
+{ 'command': 'query-cpu-model-expansion',
+  'data': { 'type': 'CpuModelExpansionType',
+            'model': 'CpuModelInfo' },
+  'returns': 'CpuModelExpansionInfo' }
+
 # @AddfdInfo:
 #
 # Information about a file descriptor that was added to an fd set.

qmp-commands.hx

@@ -3941,6 +3941,12 @@ EQMP
         .mhandler.cmd_new = qmp_marshal_query_cpu_definitions,
     },
 
+    {
+        .name       = "query-cpu-model-expansion",
+        .args_type  = "type:s,model:q",
+        .mhandler.cmd_new = qmp_marshal_query_cpu_model_expansion,
+    },
+
     {
         .name       = "query-target",
         .args_type  = "",

qmp.c

@@ -607,6 +607,13 @@ CpuDefinitionInfoList *qmp_query_cpu_definitions(Error **errp)
     return arch_query_cpu_definitions(errp);
 }
 
+CpuModelExpansionInfo *qmp_query_cpu_model_expansion(CpuModelExpansionType type,
+                                                     CpuModelInfo *model,
+                                                     Error **errp)
+{
+    return arch_query_cpu_model_expansion(type, model, errp);
+}
+
 void qmp_add_client(const char *protocol, const char *fdname,
                     bool has_skipauth, bool skipauth, bool has_tls, bool tls,
                     Error **errp)

stubs/Makefile.objs

@@ -1,4 +1,5 @@
 stub-obj-y += arch-query-cpu-def.o
+stub-obj-y += arch-query-cpu-model-expansion.o
 stub-obj-y += bdrv-next-monitor-owned.o
 stub-obj-y += blk-commit-all.o
 stub-obj-y += blockdev-close-all-bdrv-states.o

stubs/arch-query-cpu-model-expansion.c

@@ -0,0 +1,12 @@
+#include "qemu/osdep.h"
+#include "qemu-common.h"
+#include "sysemu/arch_init.h"
+#include "qapi/qmp/qerror.h"
+
+CpuModelExpansionInfo *arch_query_cpu_model_expansion(CpuModelExpansionType type,
+                                                      CpuModelInfo *mode,
+                                                      Error **errp)
+{
+    error_setg(errp, QERR_UNSUPPORTED);
+    return NULL;
+}