diff options
authorGreg Kurz <groug@kaod.org>2021-04-09 18:03:39 +0200
committerEduardo Habkost <ehabkost@redhat.com>2021-04-09 16:05:16 -0400
commit0b47ec4b95ad1952e55e639711d442f8ec6e1345 (patch)
parentcdeaed27782835a875df7365d56d69dbe7250481 (diff)
cpu/core: Fix "help" of CPU core device types
Calling qdev_get_machine() from a QOM instance_init function is fragile because we can't be sure the machine object actually exists. And this happens to break when passing ",help" on the command line to get the list of properties for a CPU core device types : $ ./qemu-system-ppc64 -device power8_v2.0-spapr-cpu-core,help qemu-system-ppc64: ../../hw/core/machine.c:1290: qdev_get_machine: Assertion `machine != NULL' failed. Aborted (core dumped) This used to work before QEMU 5.0, but commit 3df261b6676b unwillingly introduced a subtle regression : the above command line needs to create an instance but the instance_init function of the base class calls qdev_get_machine() before qemu_create_machine() has been called, which is a programming bug. Use current_machine instead. It is okay to skip the setting of nr_thread in this case since only its type is displayed. Fixes: 3df261b6676b ("softmmu/vl.c: Handle '-cpu help' and '-device help' before 'no default machine'") Reported-by: Thomas Huth <thuth@redhat.com> Signed-off-by: Greg Kurz <groug@kaod.org> Cc: peter.maydell@linaro.org Message-Id: <20210409160339.500167-3-groug@kaod.org> Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
1 files changed, 8 insertions, 2 deletions
diff --git a/hw/cpu/core.c b/hw/cpu/core.c
index 92d3b2fbad..9876075155 100644
--- a/hw/cpu/core.c
+++ b/hw/cpu/core.c
@@ -66,10 +66,16 @@ static void core_prop_set_nr_threads(Object *obj, Visitor *v, const char *name,
static void cpu_core_instance_init(Object *obj)
- MachineState *ms = MACHINE(qdev_get_machine());
CPUCore *core = CPU_CORE(obj);
- core->nr_threads = ms->smp.threads;
+ /*
+ * Only '-device something-cpu-core,help' can get us there before
+ * the machine has been created. We don't care to set nr_threads
+ * in this case since it isn't used afterwards.
+ */
+ if (current_machine) {
+ core->nr_threads = current_machine->smp.threads;
+ }
static void cpu_core_class_init(ObjectClass *oc, void *data)