[Qemu-devel] [Patch v1 25/29] qmp: add QMP interface "query-cpu-model-comparison"

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

Let's provide a standardized interface to compare two CPU models.

query-cpu-model-compare takes two models and returns what it knows about
their compability under a certain QEMU machine QEMU has been started with.

If modelA is a subset of modelB or if both are identical, modelA will run
in the same configuration as modelB. If modelA is however a superset of
modelB or if both are incompatible, one can try to create a compatible one
by "baselining" both models (follow up patch).

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                        | 65 +++++++++++++++++++++++++++++++++
 qmp-commands.hx                         |  6 +++
 qmp.c                                   |  7 ++++
 stubs/Makefile.objs                     |  1 +
 stubs/arch-query-cpu-model-comparison.c | 12 ++++++
 6 files changed, 94 insertions(+)
 create mode 100644 stubs/arch-query-cpu-model-comparison.c

diff --git a/include/sysemu/arch_init.h b/include/sysemu/arch_init.h
index 37b2e86..96d47c0 100644
--- a/include/sysemu/arch_init.h
+++ b/include/sysemu/arch_init.h
@@ -38,5 +38,8 @@ CpuDefinitionInfoList *arch_query_cpu_definitions(Error **errp);
 CpuModelExpansionInfo *arch_query_cpu_model_expansion(CpuModelExpansionType type,
                                                       CpuModelInfo *mode,
                                                       Error **errp);
+CpuModelCompareInfo *arch_query_cpu_model_comparison(CpuModelInfo *modela,
+                                                     CpuModelInfo *modelb,
+                                                     Error **errp);
 
 #endif
diff --git a/qapi-schema.json b/qapi-schema.json
index 43f7969..1f8f8ec 100644
--- a/qapi-schema.json
+++ b/qapi-schema.json
@@ -3149,6 +3149,71 @@
             'model': 'CpuModelInfo' },
   'returns': 'CpuModelExpansionInfo' }
 
+##
+# @CpuModelCompareResult:
+#
+# An enumeration of CPU model comparation results.
+#
+# @incompatible: both model definition are incompatible
+#
+# @identical: model A == model B
+#
+# @superset: model A > model B
+#
+# @subset: model A < model B
+#
+# Since: 2.8.0
+##
+{ 'enum': 'CpuModelCompareResult',
+  'data': [ 'incompatible', 'identical', 'superset', 'subset' ] }
+
+##
+# @CpuModelCompareInfo
+#
+# The result of a CPU model comparison.
+#
+# @result: The result of the compare operation.
+# @responsible-properties: List of properties that led to the comparison result
+#                          not being identical.
+#
+# @responsible-properties is a list of QOM property names that led to
+# both CPUs not being detected as identical. For identical models, this
+# list is empty.
+# If a QOM property is read-only, that means there's no known way to make the
+# CPU models identical. If the special property name "type" is included, the
+# models are by definition not identical and cannot be made identical.
+#
+# Since: 2.8.0
+##
+{ 'struct': 'CpuModelCompareInfo',
+  'data': {'result': 'CpuModelCompareResult',
+           'responsible-properties': ['str']
+          }
+}
+
+##
+# @query-cpu-model-comparison:
+#
+# Compares two CPU models, returning how they compare under a specific QEMU
+# machine.
+#
+# Note: This interface should not be used when global properties of CPU classes
+#       are changed (e.g. via "-cpu ...").
+#
+# s390x supports comparing of all CPU models. Other architectures are not
+# supported yet.
+#
+# Returns: a CpuModelBaselineInfo. Returns an error if comparing CPU models is
+#          not supported, if a model cannot be used, if a model contains
+#          an unknown cpu definition name, unknown properties or properties
+#          with wrong types.
+#
+# Since: 2.8.0
+##
+{ 'command': 'query-cpu-model-comparison',
+  'data': { 'modela': 'CpuModelInfo', 'modelb': 'CpuModelInfo' },
+  'returns': 'CpuModelCompareInfo' }
+
 # @AddfdInfo:
 #
 # Information about a file descriptor that was added to an fd set.
diff --git a/qmp-commands.hx b/qmp-commands.hx
index 7ed9528..0af2098 100644
--- a/qmp-commands.hx
+++ b/qmp-commands.hx
@@ -3948,6 +3948,12 @@ EQMP
     },
 
     {
+        .name       = "query-cpu-model-comparison",
+        .args_type  = "modela:q,modelb:q",
+        .mhandler.cmd_new = qmp_marshal_query_cpu_model_comparison,
+    },
+
+    {
         .name       = "query-target",
         .args_type  = "",
         .mhandler.cmd_new = qmp_marshal_query_target,
diff --git a/qmp.c b/qmp.c
index 29fbfb8..f551019 100644
--- a/qmp.c
+++ b/qmp.c
@@ -614,6 +614,13 @@ CpuModelExpansionInfo *qmp_query_cpu_model_expansion(CpuModelExpansionType type,
     return arch_query_cpu_model_expansion(type, model, errp);
 }
 
+CpuModelCompareInfo *qmp_query_cpu_model_comparison(CpuModelInfo *modela,
+                                                    CpuModelInfo *modelb,
+                                                    Error **errp)
+{
+    return arch_query_cpu_model_comparison(modela, modelb, 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 4929842..da768f0 100644
--- a/stubs/Makefile.objs
+++ b/stubs/Makefile.objs
@@ -1,5 +1,6 @@
 stub-obj-y += arch-query-cpu-def.o
 stub-obj-y += arch-query-cpu-model-expansion.o
+stub-obj-y += arch-query-cpu-model-comparison.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-comparison.c b/stubs/arch-query-cpu-model-comparison.c
new file mode 100644
index 0000000..d5486ae
--- /dev/null
+++ b/stubs/arch-query-cpu-model-comparison.c
@@ -0,0 +1,12 @@
+#include "qemu/osdep.h"
+#include "qemu-common.h"
+#include "sysemu/arch_init.h"
+#include "qapi/qmp/qerror.h"
+
+CpuModelCompareInfo *arch_query_cpu_model_comparison(CpuModelInfo *modela,
+                                                     CpuModelInfo *modelb,
+                                                     Error **errp)
+{
+    error_setg(errp, QERR_UNSUPPORTED);
+    return NULL;
+}
-- 
2.6.6