qapi: fill in CpuInfoFast.arch in query-cpus-fast

* Commit ca230ff33f89 added the @arch field to @CpuInfoFast, but it failed
  to set the new field in qmp_query_cpus_fast(), when TARGET_S390X was not
  defined. The updated @query-cpus-fast example in "qapi-schema.json"
  showed "arch":"x86" only because qmp_query_cpus_fast() calls g_malloc0()
  to allocate @CpuInfoFast, and the CPU_INFO_ARCH_X86 enum constant is
  generated with value 0.

  All @arch values other than @s390 implied the @CpuInfoOther sub-struct
  for @CpuInfoFast -- at the time of writing the patch --, thus no fields
  other than @arch needed to be set when TARGET_S390X was not defined. Set
  @arch now, by copying the corresponding assignments from
  qmp_query_cpus().

* Commit 25fa194b7b11 added the @riscv enum constant to @CpuInfoArch (used
  in both @CpuInfo and @CpuInfoFast -- the return types of the @query-cpus
  and @query-cpus-fast commands, respectively), and assigned, in both
  return structures, the @CpuInfoRISCV sub-structure to the new enum
  value.

  However, qmp_query_cpus_fast() would not populate either the @arch field
  or the @CpuInfoRISCV sub-structure, when TARGET_RISCV was defined; only
  qmp_query_cpus() would.

  Assign @CpuInfoOther to the @riscv enum constant in @CpuInfoFast, and
  populate only the @arch field in qmp_query_cpus_fast(). Getting CPU
  state without interrupting KVM is an exceptional thing that only S390X
  does currently. Quoting Cornelia Huck <cohuck@redhat.com>, "s390x is
  exceptional in that it has state in QEMU that is actually interesting
  for upper layers and can be retrieved without performance penalty". See
  also
  <https://www.redhat.com/archives/libvir-list/2018-February/msg00121.html>.

Cc: Cornelia Huck <cohuck@redhat.com>
Cc: Eric Blake <eblake@redhat.com>
Cc: Markus Armbruster <armbru@redhat.com>
Cc: Viktor VM Mihajlovski <mihajlov@linux.vnet.ibm.com>
Cc: qemu-stable@nongnu.org
Fixes: ca230ff33f89bf7102cbfbc2328716da6750aaed
Fixes: 25fa194b7b11901561532e435beb83d046899f7a
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <20180427192852.15013-2-lersek@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
(cherry picked from commit 96054f56396eaa0b9b5c681fc3e42a0004b17ade)
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>

cpus.c

@@ -2218,11 +2218,25 @@ CpuInfoFastList *qmp_query_cpus_fast(Error **errp)
             info->value->props = props;
         }
 
-#if defined(TARGET_S390X)
+#if defined(TARGET_I386)
+        info->value->arch = CPU_INFO_ARCH_X86;
+#elif defined(TARGET_PPC)
+        info->value->arch = CPU_INFO_ARCH_PPC;
+#elif defined(TARGET_SPARC)
+        info->value->arch = CPU_INFO_ARCH_SPARC;
+#elif defined(TARGET_MIPS)
+        info->value->arch = CPU_INFO_ARCH_MIPS;
+#elif defined(TARGET_TRICORE)
+        info->value->arch = CPU_INFO_ARCH_TRICORE;
+#elif defined(TARGET_S390X)
         s390_cpu = S390_CPU(cpu);
         env = &s390_cpu->env;
         info->value->arch = CPU_INFO_ARCH_S390;
         info->value->u.s390.cpu_state = env->cpu_state;
+#elif defined(TARGET_RISCV)
+        info->value->arch = CPU_INFO_ARCH_RISCV;
+#else
+        info->value->arch = CPU_INFO_ARCH_OTHER;
 #endif
         if (!cur_item) {
             head = cur_item = info;

qapi/misc.json

@@ -573,7 +573,7 @@
             'mips': 'CpuInfoOther',
             'tricore': 'CpuInfoOther',
             's390': 'CpuInfoS390',
-            'riscv': 'CpuInfoRISCV',
+            'riscv': 'CpuInfoOther',
             'other': 'CpuInfoOther' } }
 
 ##