cpus: Define callback for QEMU "nmi" command

This introduces an NMI (Non Maskable Interrupt) interface with
a single nmi_monitor_handler() method. A machine or a device can
implement it. This searches for an QOM object with this interface
and if it is implemented, calls it. The callback implements an action
required to cause debug crash dump on in-kernel debugger invocation.
The callback returns Error**.

This adds a nmi_monitor_handle() helper which walks through
all objects to find the interface. The interface method is called
for all found instances.

This adds support for it in qmp_inject_nmi(). Since no architecture
supports it at the moment, there is no change in behaviour.

This changes inject-nmi command description for HMP and QMP.

Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Reviewed-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

cpus.c

@@ -40,6 +40,7 @@
 #include "qemu/bitmap.h"
 #include "qemu/seqlock.h"
 #include "qapi-event.h"
+#include "hw/nmi.h"
 
 #ifndef _WIN32
 #include "qemu/compatfd.h"
@@ -1551,7 +1552,7 @@ void qmp_inject_nmi(Error **errp)
         }
     }
 #else
-    error_set(errp, QERR_UNSUPPORTED);
+    nmi_monitor_handle(monitor_get_cpu_index(), errp);
 #endif
 }
 

hmp-commands.hx

@@ -832,19 +832,17 @@ The values that can be specified here depend on the machine type, but are
 the same that can be specified in the @code{-boot} command line option.
 ETEXI
 
-#if defined(TARGET_I386) || defined(TARGET_S390X)
     {
         .name       = "nmi",
         .args_type  = "",
         .params     = "",
-        .help       = "inject an NMI on all guest's CPUs",
+        .help       = "inject an NMI",
         .mhandler.cmd = hmp_inject_nmi,
     },
-#endif
 STEXI
 @item nmi @var{cpu}
 @findex nmi
-Inject an NMI (x86) or RESTART (s390x) on the given CPU.
+Inject an NMI on the default CPU (x86/s390) or all CPUs (ppc64).
 
 ETEXI
 

hw/core/Makefile.objs

@@ -4,6 +4,7 @@ common-obj-y += fw-path-provider.o
 # irq.o needed for qdev GPIO handling:
 common-obj-y += irq.o
 common-obj-y += hotplug.o
+common-obj-y += nmi.o
 
 common-obj-$(CONFIG_EMPTY_SLOT) += empty_slot.o
 common-obj-$(CONFIG_XILINX_AXI) += stream.o

hw/core/nmi.c

@@ -0,0 +1,84 @@
+/*
+ *  NMI monitor handler class and helpers.
+ *
+ *  Copyright IBM Corp., 2014
+ *
+ *  Author: Alexey Kardashevskiy <aik@ozlabs.ru>
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2 of the License,
+ *  or (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "hw/nmi.h"
+#include "qapi/qmp/qerror.h"
+
+struct do_nmi_s {
+    int cpu_index;
+    Error *errp;
+    bool handled;
+};
+
+static void nmi_children(Object *o, struct do_nmi_s *ns);
+
+static int do_nmi(Object *o, void *opaque)
+{
+    struct do_nmi_s *ns = opaque;
+    NMIState *n = (NMIState *) object_dynamic_cast(o, TYPE_NMI);
+
+    if (n) {
+        NMIClass *nc = NMI_GET_CLASS(n);
+
+        ns->handled = true;
+        nc->nmi_monitor_handler(n, ns->cpu_index, &ns->errp);
+        if (ns->errp) {
+            return -1;
+        }
+    }
+    nmi_children(o, ns);
+
+    return 0;
+}
+
+static void nmi_children(Object *o, struct do_nmi_s *ns)
+{
+    object_child_foreach(o, do_nmi, ns);
+}
+
+void nmi_monitor_handle(int cpu_index, Error **errp)
+{
+    struct do_nmi_s ns = {
+        .cpu_index = cpu_index,
+        .errp = NULL,
+        .handled = false
+    };
+
+    nmi_children(object_get_root(), &ns);
+    if (ns.handled) {
+        error_propagate(errp, ns.errp);
+    } else {
+        error_set(errp, QERR_UNSUPPORTED);
+    }
+}
+
+static const TypeInfo nmi_info = {
+    .name          = TYPE_NMI,
+    .parent        = TYPE_INTERFACE,
+    .class_size    = sizeof(NMIClass),
+};
+
+static void nmi_register_types(void)
+{
+    type_register_static(&nmi_info);
+}
+
+type_init(nmi_register_types)

include/hw/nmi.h

@@ -0,0 +1,49 @@
+/*
+ *  NMI monitor handler class and helpers definitions.
+ *
+ *  Copyright IBM Corp., 2014
+ *
+ *  Author: Alexey Kardashevskiy <aik@ozlabs.ru>
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2 of the License,
+ *  or (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef NMI_H
+#define NMI_H 1
+
+#include "qemu-common.h"
+#include "qom/object.h"
+
+#define TYPE_NMI "nmi"
+
+#define NMI_CLASS(klass) \
+     OBJECT_CLASS_CHECK(NMIClass, (klass), TYPE_NMI)
+#define NMI_GET_CLASS(obj) \
+    OBJECT_GET_CLASS(NMIClass, (obj), TYPE_NMI)
+#define NMI(obj) \
+     INTERFACE_CHECK(NMI, (obj), TYPE_NMI)
+
+typedef struct NMIState {
+    Object parent_obj;
+} NMIState;
+
+typedef struct NMIClass {
+    InterfaceClass parent_class;
+
+    void (*nmi_monitor_handler)(NMIState *n, int cpu_index, Error **errp);
+} NMIClass;
+
+void nmi_monitor_handle(int cpu_index, Error **errp);
+
+#endif /* NMI_H */

qapi-schema.json

@@ -1186,13 +1186,13 @@
 ##
 # @inject-nmi:
 #
-# Injects an Non-Maskable Interrupt into all guest's VCPUs.
+# Injects a Non-Maskable Interrupt into the default CPU (x86/s390) or all CPUs (ppc64).
 #
 # Returns:  If successful, nothing
 #
 # Since:  0.14.0
 #
-# Notes: Only x86 Virtual Machines support this command.
+# Note: prior to 2.1, this command was only supported for x86 and s390 VMs
 ##
 { 'command': 'inject-nmi' }
 

qmp-commands.hx

@@ -477,7 +477,7 @@ SQMP
 inject-nmi
 ----------
 
-Inject an NMI on guest's CPUs.
+Inject an NMI on the default CPU (x86/s390) or all CPUs (ppc64).
 
 Arguments: None.
 
@@ -487,7 +487,6 @@ Example:
 <- { "return": {} }
 
 Note: inject-nmi fails when the guest doesn't support injecting.
-      Currently, only x86 (NMI) and s390x (RESTART) guests do.
 
 EQMP