machine: Deprecate "parameter=0" SMP configurations

In the SMP configuration, we should either provide a topology
parameter with a reasonable value (greater than zero) or just
omit it and QEMU will compute the missing value.

The users shouldn't provide a configuration with any parameter
of it specified as zero (e.g. -smp 8,sockets=0) which could
possibly cause unexpected results in the -smp parsing. So we
deprecate this kind of configurations since 6.2 by adding the
explicit sanity check.

Signed-off-by: Yanan Wang <wangyanan55@huawei.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Message-Id: <20210929025816.21076-3-wangyanan55@huawei.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 14 insertions, 0 deletions

diff --git a/hw/core/machine.c b/hw/core/machine.c
index 067f42b528..4e409261c9 100644
--- a/hw/core/machine.c
+++ b/hw/core/machine.c
@@ -835,6 +835,20 @@ static void machine_set_smp(Object *obj, Visitor *v, const char *name,
         return;
     }
 
+    /*
+     * Specified CPU topology parameters must be greater than zero,
+     * explicit configuration like "cpus=0" is not allowed.
+     */
+    if ((config->has_cpus && config->cpus == 0) ||
+        (config->has_sockets && config->sockets == 0) ||
+        (config->has_dies && config->dies == 0) ||
+        (config->has_cores && config->cores == 0) ||
+        (config->has_threads && config->threads == 0) ||
+        (config->has_maxcpus && config->maxcpus == 0)) {
+        warn_report("Deprecated CPU topology (considered invalid): "
+                    "CPU topology parameters must be greater than zero");
+    }
+
     mc->smp_parse(ms, config, errp);
     if (*errp) {
         goto out_free;