s390: wire up nmi command to raise a RESTART interrupt on S390

There is the 'nmi' command that is used to trigger a guest dump via kdump feature on x86.
s390 uses RESTART interrupt to trigger kdump.
So, this patch provides a mean to use 'nmi' command on s390 to raise RESTART interrupt.

The CPU to receive the RESTART interrupt is the "default" one.

There is an infrastructure to select the "default" CPU using 'cpu' command.
The 'info cpus' command can be used to see which one is the "default".

In order to wire up the RESTART to 'nmi' command we had to:
1. implement the kvm_s390_cpu_restart function by exporting the existing code
2. implement s390_cpu_restart function as kvm-aware wrapper
3. modify the qmp_inject_nmi function to enable (for s390) the scan for
   "default" CPU and call s390_cpu_restart for it;
3. fix some messages.

Signed-off-by: Eugene (jno) Dvurechenski <jno@linux.vnet.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Acked-by: Alexander Graf <agraf@suse.de>

cpus.c

@@ -1401,6 +1401,20 @@ void qmp_inject_nmi(Error **errp)
             apic_deliver_nmi(env->apic_state);
         }
     }
+#elif defined(TARGET_S390X)
+    CPUState *cs;
+    S390CPU *cpu;
+
+    for (cs = first_cpu; cs != NULL; cs = cs->next_cpu) {
+        cpu = S390_CPU(cs);
+        if (cpu->env.cpu_num == monitor_get_cpu_index()) {
+            if (s390_cpu_restart(S390_CPU(cs)) == -1) {
+                error_set(errp, QERR_UNSUPPORTED);
+                return;
+            }
+            break;
+        }
+    }
 #else
     error_set(errp, QERR_UNSUPPORTED);
 #endif

hmp-commands.hx

@@ -822,7 +822,7 @@ 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)
+#if defined(TARGET_I386) || defined(TARGET_S390X)
     {
         .name       = "nmi",
         .args_type  = "",
@@ -834,7 +834,7 @@ ETEXI
 STEXI
 @item nmi @var{cpu}
 @findex nmi
-Inject an NMI on the given CPU (x86 only).
+Inject an NMI (x86) or RESTART (s390x) on the given CPU.
 
 ETEXI
 

qmp-commands.hx

@@ -487,7 +487,7 @@ Example:
 <- { "return": {} }
 
 Note: inject-nmi fails when the guest doesn't support injecting.
-      Currently, only x86 guests do.
+      Currently, only x86 (NMI) and s390x (RESTART) guests do.
 
 EQMP
 

target-s390x/cpu.h

@@ -1069,6 +1069,7 @@ void kvm_s390_enable_css_support(S390CPU *cpu);
 int kvm_s390_get_registers_partial(CPUState *cpu);
 int kvm_s390_assign_subch_ioeventfd(EventNotifier *notifier, uint32_t sch,
                                     int vq, bool assign);
+int kvm_s390_cpu_restart(S390CPU *cpu);
 #else
 static inline void kvm_s390_io_interrupt(S390CPU *cpu,
                                         uint16_t subchannel_id,
@@ -1093,8 +1094,20 @@ static inline int kvm_s390_assign_subch_ioeventfd(EventNotifier *notifier,
 {
     return -ENOSYS;
 }
+static inline int kvm_s390_cpu_restart(S390CPU *cpu)
+{
+    return -ENOSYS;
+}
 #endif
 
+static inline int s390_cpu_restart(S390CPU *cpu)
+{
+    if (kvm_enabled()) {
+        return kvm_s390_cpu_restart(cpu);
+    }
+    return -ENOSYS;
+}
+
 static inline void s390_io_interrupt(S390CPU *cpu,
                                      uint16_t subchannel_id,
                                      uint16_t subchannel_nr,

target-s390x/kvm.c

@@ -612,12 +612,12 @@ static int handle_diag(S390CPU *cpu, struct kvm_run *run, int ipb_code)
     return r;
 }
 
-static int s390_cpu_restart(S390CPU *cpu)
+int kvm_s390_cpu_restart(S390CPU *cpu)
 {
     kvm_s390_interrupt(cpu, KVM_S390_RESTART, 0);
     s390_add_running_cpu(cpu);
     qemu_cpu_kick(CPU(cpu));
-    DPRINTF("DONE: SIGP cpu restart: %p\n", &cpu->env);
+    DPRINTF("DONE: KVM cpu restart: %p\n", &cpu->env);
     return 0;
 }
 
@@ -686,7 +686,7 @@ static int handle_sigp(S390CPU *cpu, struct kvm_run *run, uint8_t ipa1)
 
     switch (order_code) {
         case SIGP_RESTART:
-            r = s390_cpu_restart(target_cpu);
+            r = kvm_s390_cpu_restart(target_cpu);
             break;
         case SIGP_STORE_STATUS_ADDR:
             r = s390_store_status(target_env, parameter);