[libvirt] [Qemu-devel] [PATCH v5 2/2] vl:c: make sure that sockets are calculated correctly in '-smp X' case

[Igor Mammedov]

On Tue, 4 Sep 2018 22:40:49 -0300
Eduardo Habkost <ehabkost at redhat.com> wrote:

> On Tue, Sep 04, 2018 at 05:18:48PM +0200, Andrew Jones wrote:
> > On Tue, Sep 04, 2018 at 03:22:36PM +0200, Igor Mammedov wrote:
> > > commit
> > >   (5cdc9b76e3 vl.c: Remove dead assignment)
> > > removed sockets calculation when 'sockets' weren't provided on CLI
> > > since there wasn't any users for it back then. Exiting checks
> > > are neither reachable
> > >    } else if (sockets * cores * threads < cpus) {
> > > or nor triggable
> > >    if (sockets * cores * threads > max_cpus)
> > > so we weren't noticing wrong topology since then, since users
> > > recalculate sockets adhoc on their own.
> > > 
> > > However with deprecation check it becomes noticable, for example
> > >   -smp 2
> > > will start printing warning:
> > >   "warning: Invalid CPU topology deprecated: sockets (1) * cores (1) * threads (1) != maxcpus (2)"
> > > calculating sockets if they weren't specified.
> > > 
> > > Fix it by returning back sockets calculation if it's omited on CLI.
> > > 
> > > Signed-off-by: Igor Mammedov <imammedo at redhat.com>
> > > ---
> > >  vl.c | 5 ++++-
> > >  1 file changed, 4 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/vl.c b/vl.c
> > > index 7fd700e..333d638 100644
> > > --- a/vl.c
> > > +++ b/vl.c
> > > @@ -1210,11 +1210,14 @@ static void smp_parse(QemuOpts *opts)
> > >  
> > >          /* compute missing values, prefer sockets over cores over threads */
> > >          if (cpus == 0 || sockets == 0) {
> > > -            sockets = sockets > 0 ? sockets : 1;
> > >              cores = cores > 0 ? cores : 1;
> > >              threads = threads > 0 ? threads : 1;
> > >              if (cpus == 0) {
> > > +                sockets = sockets > 0 ? sockets : 1;
> > >                  cpus = cores * threads * sockets;
> > > +            } else {
> > > +                max_cpus = qemu_opt_get_number(opts, "maxcpus", cpus);
> > > +                sockets = !sockets ? max_cpus / (cores * threads) : sockets;
> 
> Why the !sockets check here?  If we have reached this statement
> we know that (cpus == 0 || sockets == 0) is true and
> (cpus == 0) is false, so sockets is guaranteed to be 0.
Indeed, thanks for spotting it
I'll fix it up and respin

> 
> Sorry for not spotting this earlier.
> 
> > >              }
> > >          } else if (cores == 0) {
> > >              threads = threads > 0 ? threads : 1;
> > > -- 
> > > 2.7.4
> > > 
> > >
> >  
> > Reviewed-by: Andrew Jones <drjones at redhat.com>
>