[Qemu-devel] [PATCH] vl: verify if combination of cpus, sockets, cores and threads is sane

[Peter Lieven <pl@kamp.de>]

Signed-off-by: Peter Lieven <pl@kamp.de>
---
 vl.c |   34 ++++++++++++++++++++--------------
 1 file changed, 20 insertions(+), 14 deletions(-)

diff --git a/vl.c b/vl.c
index 8d5d874..dc0b41a 100644
--- a/vl.c
+++ b/vl.c
@@ -1385,35 +1385,41 @@ static QemuOptsList qemu_smp_opts = {
 static void smp_parse(QemuOpts *opts)
 {
     if (opts) {
-
         unsigned cpus    = qemu_opt_get_number(opts, "cpus", 0);
         unsigned sockets = qemu_opt_get_number(opts, "sockets", 0);
         unsigned cores   = qemu_opt_get_number(opts, "cores", 0);
         unsigned threads = qemu_opt_get_number(opts, "threads", 0);
 
         /* compute missing values, prefer sockets over cores over threads */
-        if (cpus == 0 || sockets == 0) {
+        if (cpus == 0) {
             sockets = sockets > 0 ? sockets : 1;
             cores = cores > 0 ? cores : 1;
             threads = threads > 0 ? threads : 1;
-            if (cpus == 0) {
-                cpus = cores * threads * sockets;
-            }
+            cpus = cores * threads * sockets;
+        } else if (sockets == 0) {
+            cores = cores > 0 ? cores : 1;
+            threads = threads > 0 ? threads : 1;
+            sockets = cpus / (cores * threads);
+        } else if (cores == 0) {
+            threads = threads > 0 ? threads : 1;
+            cores = cpus / (sockets * threads);
         } else {
-            if (cores == 0) {
-                threads = threads > 0 ? threads : 1;
-                cores = cpus / (sockets * threads);
-            } else {
-                threads = cpus / (cores * sockets);
-            }
+            threads = cpus / (sockets * cores);
         }
 
-        max_cpus = qemu_opt_get_number(opts, "maxcpus", 0);
+        if (cpus != sockets * cores * threads) {
+            fprintf(stderr, "Illegal CPU layout: %d cpus with %d sockets,"
+                            " %d cores per socket and %d threads per core"
+                            " (cpus != sockets * cores * threads)\n",
+                            cpus, sockets, cores, threads);
+            exit(1);
+        }
 
         smp_cpus = cpus;
-        smp_cores = cores > 0 ? cores : 1;
-        smp_threads = threads > 0 ? threads : 1;
+        smp_cores = cores;
+        smp_threads = threads;
 
+        max_cpus = qemu_opt_get_number(opts, "maxcpus", 0);
     }
 
     if (max_cpus == 0) {
-- 
1.7.9.5