[Qemu-discuss] Guests don't start with qemu 2.1.0: smbios_get_tables: Assertion `smbios_smp_sockets >= 1' failed

[Brian Rak]

I've been testing 2.1.0, and qemu will no longer start up with our CPU 
configuration.  I get the error:

qemu-kvm: /root/qemu/src/hw/i386/smbios.c:825: smbios_get_tables: 
Assertion `smbios_smp_sockets >= 1' failed.

The relevant parts of my command line:

-smp 4,sockets=2,cores=12,threads=2

This is ultimately coming from my libvirt config of:

  <vcpu placement='static'>4</vcpu>
  <cpu mode='custom' match='exact'>
    <topology sockets='2' cores='12' threads='2'/>
  </cpu>


Is this configuration no longer supported?  Up until 2.1.0, this was 
handled well.. for any CPU count < 12, I got one socket with the correct 
number of cores.  For anything over 12 vcpus, I got two sockets.  This 
makes Windows licensing happy.

I took a look at the code, and it seems like it should just cap the 
minimum number of sockets at 1, rather then this assert.

--- ../src_clean/hw/i386/smbios.c       2014-08-01 10:12:17.000000000 -0400
+++ hw/i386/smbios.c    2014-08-12 14:39:40.560485901 -0400
@@ -822,7 +822,7 @@
         smbios_build_type_3_table();

         smbios_smp_sockets = smp_cpus / (smp_cores * smp_threads);
-        assert(smbios_smp_sockets >= 1);
+       if (smbios_smp_sockets < 1) smbios_smp_sockets = 1;

         for (i = 0; i < smbios_smp_sockets; i++) {
             smbios_build_type_4_table(i);

Is there a downside to this patch?