machine: Uniformly use maxcpus to calculate the omitted parameters

We are currently using maxcpus to calculate the omitted sockets
but using cpus to calculate the omitted cores/threads. This makes
cmdlines like:
  -smp cpus=8,maxcpus=16
  -smp cpus=8,cores=4,maxcpus=16
  -smp cpus=8,threads=2,maxcpus=16
work fine but the ones like:
  -smp cpus=8,sockets=2,maxcpus=16
  -smp cpus=8,sockets=2,cores=4,maxcpus=16
  -smp cpus=8,sockets=2,threads=2,maxcpus=16
break the sanity check.

Since we require for a valid config that the product of "sockets * cores
* threads" should equal to the maxcpus, we should uniformly use maxcpus
to calculate their omitted values.

Also the if-branch of "cpus == 0 || sockets == 0" was split into two
branches of "cpus == 0" and "sockets == 0" so that we can clearly read
that we are parsing the configuration with a preference on cpus over
sockets over cores over threads.

Note: change in this patch won't affect any existing working cmdlines
but improves consistency and allows more incomplete configs to be valid.

Signed-off-by: Yanan Wang <wangyanan55@huawei.com>
Reviewed-by: Andrew Jones <drjones@redhat.com>
Reviewed-by: Pankaj Gupta <pankaj.gupta@ionos.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Message-Id: <20210929025816.21076-5-wangyanan55@huawei.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 15 insertions, 15 deletions

diff --git a/hw/core/machine.c b/hw/core/machine.c
index 8e719e2932..596e758133 100644
--- a/hw/core/machine.c
+++ b/hw/core/machine.c
@@ -760,24 +760,26 @@ static void smp_parse(MachineState *ms, SMPConfiguration *config, Error **errp)
     }
 
     /* compute missing values, prefer sockets over cores over threads */
-    if (cpus == 0 || sockets == 0) {
+    maxcpus = maxcpus > 0 ? maxcpus : cpus;
+
+    if (cpus == 0) {
+        sockets = sockets > 0 ? sockets : 1;
         cores = cores > 0 ? cores : 1;
         threads = threads > 0 ? threads : 1;
-        if (cpus == 0) {
-            sockets = sockets > 0 ? sockets : 1;
-            cpus = cores * threads * sockets;
-        } else {
-            maxcpus = maxcpus > 0 ? maxcpus : cpus;
-            sockets = maxcpus / (cores * threads);
-        }
+        cpus = sockets * cores * threads;
+        maxcpus = maxcpus > 0 ? maxcpus : cpus;
+    } else if (sockets == 0) {
+        cores = cores > 0 ? cores : 1;
+        threads = threads > 0 ? threads : 1;
+        sockets = maxcpus / (cores * threads);
     } else if (cores == 0) {
         threads = threads > 0 ? threads : 1;
-        cores = cpus / (sockets * threads);
-        cores = cores > 0 ? cores : 1;
+        cores = maxcpus / (sockets * threads);
     } else if (threads == 0) {
-        threads = cpus / (cores * sockets);
-        threads = threads > 0 ? threads : 1;
-    } else if (sockets * cores * threads < cpus) {
+        threads = maxcpus / (sockets * cores);
+    }
+
+    if (sockets * cores * threads < cpus) {
         error_setg(errp, "cpu topology: "
                    "sockets (%u) * cores (%u) * threads (%u) < "
                    "smp_cpus (%u)",
@@ -785,8 +787,6 @@ static void smp_parse(MachineState *ms, SMPConfiguration *config, Error **errp)
         return;
     }
 
-    maxcpus = maxcpus > 0 ? maxcpus : cpus;
-
     if (maxcpus < cpus) {
         error_setg(errp, "maxcpus must be equal to or greater than smp");
         return;