[Qemu-devel] [PATCH 2/6] qapi: handle the riscv CpuInfoArch in query-cpus-fast

[Laszlo Ersek <lersek@redhat.com>]

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.

In theory, there are two ways to fix this:

(a) Fill in both the @arch field and the @CpuInfoRISCV sub-structure in
    qmp_query_cpus_fast(), by copying the logic from qmp_query_cpus().

(b) Assign @CpuInfoOther to the @riscv enum constant in @CpuInfoFast, and
    populate only the @arch field in qmp_query_cpus_fast().

Approach (b) seems more robust, because:

- clearly there has never been an attempt to get actual RISV CPU state
  from qmp_query_cpus_fast(), so its lack of RISCV support is not actually
  a problem,

- getting CPU state without interrupting KVM looks like an exceptional
  thing to do (only S390X does it currently).

Cc: Bastian Koppelmann <kbastian@mail.uni-paderborn.de>
Cc: Eric Blake <eblake@redhat.com>
Cc: Laurent Vivier <laurent@vivier.eu>
Cc: Markus Armbruster <armbru@redhat.com>
Cc: Michael Clark <mjc@sifive.com>
Cc: Palmer Dabbelt <palmer@sifive.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Peter Crosthwaite <crosthwaite.peter@gmail.com>
Cc: Richard Henderson <rth@twiddle.net>
Cc: Riku Voipio <riku.voipio@iki.fi>
Cc: Sagar Karandikar <sagark@eecs.berkeley.edu>
Cc: qemu-stable@nongnu.org
Fixes: 25fa194b7b11901561532e435beb83d046899f7a
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
---

Notes:
    PATCHv1:
    
    - new patch

 qapi/misc.json | 2 +-
 cpus.c         | 2 ++
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/qapi/misc.json b/qapi/misc.json
index 5636f4a14997..104d013adba6 100644
--- a/qapi/misc.json
+++ b/qapi/misc.json
@@ -565,23 +565,23 @@
 { 'union': 'CpuInfoFast',
   'base': {'cpu-index': 'int', 'qom-path': 'str',
            'thread-id': 'int', '*props': 'CpuInstanceProperties',
            'arch': 'CpuInfoArch' },
   'discriminator': 'arch',
   'data': { 'x86': 'CpuInfoOther',
             'sparc': 'CpuInfoOther',
             'ppc': 'CpuInfoOther',
             'mips': 'CpuInfoOther',
             'tricore': 'CpuInfoOther',
             's390': 'CpuInfoS390',
-            'riscv': 'CpuInfoRISCV',
+            'riscv': 'CpuInfoOther',
             'other': 'CpuInfoOther' } }
 
 ##
 # @query-cpus-fast:
 #
 # Returns information about all virtual CPUs. This command does not
 # incur a performance penalty and should be used in production
 # instead of query-cpus.
 #
 # Returns: list of @CpuInfoFast
 #
diff --git a/cpus.c b/cpus.c
index 1a9a2edee1f2..60563a6d54ec 100644
--- a/cpus.c
+++ b/cpus.c
@@ -2225,22 +2225,24 @@ CpuInfoFastList *qmp_query_cpus_fast(Error **errp)
 #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;
         } else {
             cur_item->next = info;
             cur_item = info;
         }
     }
 
-- 
2.14.1.3.gb7cf6e02401b