[PATCH 1/6] accel: Introduce 'query-accels' QMP command

["Philippe Mathieu-Daudé" <philmd@redhat.com>]

Introduce the 'query-accels' QMP command which returns a list
of built-in accelerators names.

- Accelerator is an QAPI enum of all existing accelerators,

- AcceleratorInfo is a QAPI structure providing accelerator
  specific information. Currently the common structure base
  provides the name of the accelerator, while the specific
  part is empty, but each accelerator can expand it.

- 'query-accels' QMP command returns a list of @AcceleratorInfo

For example on a KVM-only build we get:

    { "execute": "query-accels" }
    {
        "return": [
            {
                "type": "qtest"
            },
            {
                "type": "kvm"
            }
        ]
    }

Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
---
 qapi/machine.json | 55 +++++++++++++++++++++++++++++++++++++++++++++++
 accel/accel-qmp.c | 47 ++++++++++++++++++++++++++++++++++++++++
 accel/meson.build |  2 +-
 3 files changed, 103 insertions(+), 1 deletion(-)
 create mode 100644 accel/accel-qmp.c

diff --git a/qapi/machine.json b/qapi/machine.json
index 330189efe3d..ffbf28e5d50 100644
--- a/qapi/machine.json
+++ b/qapi/machine.json
@@ -1471,3 +1471,58 @@
 ##
 { 'event': 'MEM_UNPLUG_ERROR',
   'data': { 'device': 'str', 'msg': 'str' } }
+
+##
+# @Accelerator:
+#
+# An enumeration of accelerator names.
+#
+# Since: 6.0
+##
+{ 'enum': 'Accelerator',
+  'data': [ { 'name': 'qtest' },
+            { 'name': 'tcg' },
+            { 'name': 'kvm' },
+            { 'name': 'hax' },
+            { 'name': 'hvf' },
+            { 'name': 'whpx' },
+            { 'name': 'xen' } ] }
+
+##
+# @AcceleratorInfo:
+#
+# Accelerator information.
+#
+# @name: The accelerator name.
+#
+# Since: 6.0
+##
+{ 'union': 'AcceleratorInfo',
+  'base': {'name': 'Accelerator'},
+  'discriminator': 'name',
+  'data': { } }
+
+##
+# @query-accels:
+#
+# Get a list of AcceleratorInfo for all built-in accelerators.
+#
+# Returns: a list of @AcceleratorInfo describing each accelerator.
+#
+# Since: 6.0
+#
+# Example:
+#
+# -> { "execute": "query-accels" }
+# <- { "return": [
+#        {
+#            "type": "qtest"
+#        },
+#        {
+#            "type": "kvm"
+#        }
+#    ] }
+#
+##
+{ 'command': 'query-accels',
+  'returns': ['AcceleratorInfo'] }
diff --git a/accel/accel-qmp.c b/accel/accel-qmp.c
new file mode 100644
index 00000000000..f16e49b8956
--- /dev/null
+++ b/accel/accel-qmp.c
@@ -0,0 +1,47 @@
+/*
+ * QEMU accelerators, QMP commands
+ *
+ * Copyright (c) 2021 Red Hat Inc.
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+
+#include "qemu/osdep.h"
+#include "qapi/qapi-commands-machine.h"
+
+static const Accelerator accel_list[] = {
+    ACCELERATOR_QTEST,
+#ifdef CONFIG_TCG
+    ACCELERATOR_TCG,
+#endif
+#ifdef CONFIG_KVM
+    ACCELERATOR_KVM,
+#endif
+#ifdef CONFIG_HAX
+    ACCELERATOR_HAX,
+#endif
+#ifdef CONFIG_HVF
+    ACCELERATOR_HVF,
+#endif
+#ifdef CONFIG_WHPX
+    ACCELERATOR_WHPX,
+#endif
+#ifdef CONFIG_XEN_BACKEND
+    ACCELERATOR_XEN,
+#endif
+};
+
+AcceleratorInfoList *qmp_query_accels(Error **errp)
+{
+    AcceleratorInfoList *list = NULL, **tail = &list;
+
+    for (unsigned i = 0; i < ARRAY_SIZE(accel_list); i++) {
+        AcceleratorInfo *info = g_new0(AcceleratorInfo, 1);
+
+        info->name = accel_list[i];
+
+        QAPI_LIST_APPEND(tail, info);
+    }
+
+    return list;
+}
diff --git a/accel/meson.build b/accel/meson.build
index b44ba30c864..7a48f6d568d 100644
--- a/accel/meson.build
+++ b/accel/meson.build
@@ -1,4 +1,4 @@
-specific_ss.add(files('accel-common.c'))
+specific_ss.add(files('accel-common.c', 'accel-qmp.c'))
 softmmu_ss.add(files('accel-softmmu.c'))
 user_ss.add(files('accel-user.c'))
 
-- 
2.26.2