[Qemu-devel] [Patch v1 24/29] qmp: add QMP interface "query-cpu-model-expansion"

[David Hildenbrand <dahi@linux.vnet.ibm.com>]

Let's provide a standardized interface to expand CPU models, like the
host model. This interface can be used by tooling to get details about a
specific CPU model, e.g. 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>
Signed-off-by: David Hildenbrand <dahi@linux.vnet.ibm.com>
---
 include/sysemu/arch_init.h             |  3 ++
 qapi-schema.json                       | 86 ++++++++++++++++++++++++++++++++++
 qmp-commands.hx                        |  6 +++
 qmp.c                                  |  7 +++
 stubs/Makefile.objs                    |  1 +
 stubs/arch-query-cpu-model-expansion.c | 12 +++++
 6 files changed, 115 insertions(+)
 create mode 100644 stubs/arch-query-cpu-model-expansion.c

diff --git a/include/sysemu/arch_init.h b/include/sysemu/arch_init.h
index d690dfa..37b2e86 100644
--- a/include/sysemu/arch_init.h
+++ b/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
diff --git a/qapi-schema.json b/qapi-schema.json
index 3f50c1d..43f7969 100644
--- a/qapi-schema.json
+++ b/qapi-schema.json
@@ -3063,6 +3063,92 @@
 ##
 { '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 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
+#          QEMU version or compatibility machines. Therefore, the resulting
+#          model can be used by tooling without having to specify a
+#          compatibility machine - e.g. when displaying the "host" model.
+#          All 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 the given CPU model to different granularities, allowing tooling
+# to get an understanding what a specific CPU model looks like in QEMU
+# under a certain QEMU machine.
+#
+# Expanding CPU models is in general independant of the accelerator, except
+# for models like "host" that explicitly rely on an accelerator and can
+# vary in different configurations. This interface can therefore also be used
+# to query the "host" CPU model.
+#
+# Note: This interface should not be used when global properties of CPU classes
+#       are changed (e.g. via "-cpu ...").
+#
+# s390x supports expanding of all CPU models with all expansion types. Other
+# architectures are not supported yet.
+#
+# 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.
diff --git a/qmp-commands.hx b/qmp-commands.hx
index c8d360a..7ed9528 100644
--- a/qmp-commands.hx
+++ b/qmp-commands.hx
@@ -3942,6 +3942,12 @@ EQMP
     },
 
     {
+        .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  = "",
         .mhandler.cmd_new = qmp_marshal_query_target,
diff --git a/qmp.c b/qmp.c
index b6d531e..29fbfb8 100644
--- a/qmp.c
+++ b/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)
diff --git a/stubs/Makefile.objs b/stubs/Makefile.objs
index 55edd15..4929842 100644
--- a/stubs/Makefile.objs
+++ b/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
diff --git a/stubs/arch-query-cpu-model-expansion.c b/stubs/arch-query-cpu-model-expansion.c
new file mode 100644
index 0000000..ae7cf55
--- /dev/null
+++ b/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;
+}
-- 
2.6.6