[Qemu-devel] [PATCH] Add another sanity check to smp_parse() function

[Thomas Huth <thuth@redhat.com>]

The code in smp_parse already checks the topology information for
sockets * cores * threads < cpus and bails out with an error in
that case. However, it is still possible to supply a bad configuration
the other way round, e.g. with:

 qemu-system-xxx -smp 4,sockets=1,cores=4,threads=2

QEMU then still starts the guest, with topology configuration that
is rather incomprehensible and likely not what the user wanted.
So let's add another check to refuse such wrong configurations.

Signed-off-by: Thomas Huth <thuth@redhat.com>
---
 vl.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/vl.c b/vl.c
index 5856396..c8d24b1 100644
--- a/vl.c
+++ b/vl.c
@@ -1224,7 +1224,13 @@ static void smp_parse(QemuOpts *opts)
             exit(1);
         }
 
-        max_cpus = qemu_opt_get_number(opts, "maxcpus", 0);
+        max_cpus = qemu_opt_get_number(opts, "maxcpus", cpus);
+        if (sockets * cores * threads > max_cpus) {
+            fprintf(stderr, "cpu topology: error: "
+                    "sockets (%u) * cores (%u) * threads (%u) > maxcpus (%u)\n",
+                    sockets, cores, threads, max_cpus);
+            exit(1);
+        }
 
         smp_cpus = cpus;
         smp_cores = cores > 0 ? cores : 1;
-- 
1.8.3.1