[Qemu-devel] [PATCH v7 1/4] arm: qmp: add query-gic-capabilities interface

[Peter Xu]

This patch add "query-gic-capabilities" but does not implemnet it. The
command is ARM-only. The command will return a list of GICCapability
struct that describes all GIC versions that current QEMU and system
support.

Libvirt is possibly the first consumer of this new command.

Before this patch, user will successfully configure all kinds of GIC
devices for ARM guests, no matter whether current QEMU/kernel support
it. If the specified GIC version/type is not supported, user will got an
ambiguous "QEMU boot failure" when trying to start the VM. This is not
user-friendly.

With this patch, libvirt should be able to query which type (and which
version) of GIC device that we support. Use this information, libvirt
can warn the user during configuration of guests when specified GIC
device type is not supported. Or better, we can just list those versions
that we support, and filter out those not-supported ones.

For example, if we got the query result:

{"return": [{"emulated": false, "version": 3, "kernel": true},
            {"emulated": true, "version": 2, "kernel": false}]}

Then it means that we support emulated GIC version 2 using:

  qemu-system-aarch64 -M virt,accel=tcg,gic-version=2 ...

or kvm-accelerated GIC version 3 using:

  qemu-system-aarch64 -M virt,accel=kvm,gic-version=3 ...

If we specify other explicit GIC version rather than the above, QEMU
will not be able to boot.

Besides, the community is working on a more generic way to query these
kind of information. However, due to the eagerness of this command, we
decided to first implement this ad-hoc one, then when the generic method
is ready, we can move on to that one smoothly.

Signed-off-by: Peter Xu <address@hidden>
---
 monitor.c                |  8 ++++++++
 qapi-schema.json         | 36 ++++++++++++++++++++++++++++++++++++
 qmp-commands.hx          | 27 +++++++++++++++++++++++++++
 target-arm/Makefile.objs |  2 +-
 target-arm/monitor.c     | 28 ++++++++++++++++++++++++++++
 5 files changed, 100 insertions(+), 1 deletion(-)
 create mode 100644 target-arm/monitor.c

diff --git a/monitor.c b/monitor.c
index 4c02f0f..5f2be8b 100644
--- a/monitor.c
+++ b/monitor.c
@@ -4258,3 +4258,11 @@ void qmp_dump_skeys(const char *filename, Error **errp)
     error_setg(errp, QERR_FEATURE_DISABLED, "dump-skeys");
 }
 #endif
+
+#ifndef TARGET_ARM
+GICCapabilityList *qmp_query_gic_capabilities(Error **errp)
+{
+    error_setg(errp, QERR_FEATURE_DISABLED, "query-gic-capabilities");
+    return NULL;
+}
+#endif
diff --git a/qapi-schema.json b/qapi-schema.json
index 88f9b81..19921d5 100644
--- a/qapi-schema.json
+++ b/qapi-schema.json
@@ -4126,3 +4126,39 @@
 ##
 { 'enum': 'ReplayMode',
   'data': [ 'none', 'record', 'play' ] }
+
+##
+# @GICCapability:
+#
+# The struct describes capability for a specific GIC (Generic
+# Interrupt Controller) version. These bits are not only decided by
+# QEMU/KVM software version, but also decided by the hardware that
+# the program is running upon.
+#
+# @version:  version of GIC to be described. Currently, only 2 and 3
+#            are supported.
+#
+# @emulated: whether current QEMU/hardware supports emulated GIC
+#            device in user space.
+#
+# @kernel:   whether current QEMU/hardware supports hardware
+#            accelerated GIC device in kernel.
+#
+# Since: 2.6
+##
+{ 'struct': 'GICCapability',
+  'data': { 'version': 'int',
+            'emulated': 'bool',
+            'kernel': 'bool' } }
+
+##
+# @query-gic-capabilities:
+#
+# This command is ARM-only. It will return a list of GICCapability
+# objects that describe its capability bits.
+#
+# Returns: a list of GICCapability objects.
+#
+# Since: 2.6
+##
+{ 'command': 'query-gic-capabilities', 'returns': ['GICCapability'] }
diff --git a/qmp-commands.hx b/qmp-commands.hx
index 9e05365..de896a5 100644
--- a/qmp-commands.hx
+++ b/qmp-commands.hx
@@ -4853,3 +4853,30 @@ Example:
                  {"type": 0, "out-pport": 0, "pport": 0, "vlan-id": 3840,
                   "pop-vlan": 1, "id": 251658240}
    ]}
+
+EQMP
+
+#if defined TARGET_ARM
+    {
+        .name       = "query-gic-capabilities",
+        .args_type  = "",
+        .mhandler.cmd_new = qmp_marshal_query_gic_capabilities,
+    },
+#endif
+
+SQMP
+query-gic-capabilities
+---------------
+
+Return a list of GICCapability objects, describing supported GIC
+(Generic Interrupt Controller) versions.
+
+Arguments: None
+
+Example:
+
+-> { "execute": "query-gic-capabilities" }
+<- { "return": [{ "version": 2, "emulated": true, "kernel": false },
+                { "version": 3, "emulated": false, "kernel": true } ] }
+
+EQMP
diff --git a/target-arm/Makefile.objs b/target-arm/Makefile.objs
index a80eb39..334074c 100644
--- a/target-arm/Makefile.objs
+++ b/target-arm/Makefile.objs
@@ -8,4 +8,4 @@ obj-y += translate.o op_helper.o helper.o cpu.o
 obj-y += neon_helper.o iwmmxt_helper.o
 obj-y += gdbstub.o
 obj-$(TARGET_AARCH64) += cpu64.o translate-a64.o helper-a64.o gdbstub64.o
-obj-y += crypto_helper.o
+obj-y += crypto_helper.o monitor.o
diff --git a/target-arm/monitor.c b/target-arm/monitor.c
new file mode 100644
index 0000000..4c9bef3
--- /dev/null
+++ b/target-arm/monitor.c
@@ -0,0 +1,28 @@
+/*
+ * QEMU monitor.c for ARM.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to 
deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING 
FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+#include "qemu/osdep.h"
+#include "qmp-commands.h"
+
+GICCapabilityList *qmp_query_gic_capabilities(Error **errp)
+{
+    return NULL;
+}
-- 
2.4.3