On Wed, Jul 22, 2015 at 03:59:50PM +0200, Thomas Huth wrote:
> 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 <th...@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);
> + }
I am always afraid of breaking existing setups when we do that, because
there may be existing VMs running with these weird configurations, and
people won't be able to live-migrate them to a newer QEMU.
But I think we really have to start refusing to run obviously broken
configurations one day, or we will never fix this mess, so:
Reviewed-by: Eduardo Habkost <ehabk...@redhat.com>
I want to apply this through the x86 tree, but I would like to get some
Acked-by from other maintainers first.
--
Eduardo
