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

[Brian Rak]

On 8/13/2014 7:33 AM, Jakob Bohm wrote:
> On 8/12/2014 8:40 PM, Brian Rak wrote:
> > 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?
>
> Have you checked why the variable is 0 and not 1 (or 2), maybe there is
> a deeper bug which leaves it at 0, even when it should be 2 (or more).
>
> Remember, the place that reports an error is rarely the cause of the
> problem.
>
> Enjoy
>
> Jakob

My command line is this:

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

Which means, we get:

smbios_smp_sockets = 4 / (12 * 2) = 0.1666

Which means the assert is correct.  This has been a valid configuration 
of CPUs/cores up until 2.1.0.  I'd have to go update the config on all 
of our instances if I wanted to upgrade without this patch :/