Re: [Qemu-devel] [PATCH v1 08/11] s390x: allow only 1 CPU with TCG

[Cornelia Huck]

On Thu, 31 Aug 2017 17:03:21 +0200
David Hildenbrand <address@hidden> wrote:

> On 31.08.2017 16:41, Cornelia Huck wrote:
> > On Wed, 30 Aug 2017 19:05:58 +0200
> > David Hildenbrand <address@hidden> wrote:
> >   
> >> Specifying more than 1 CPU (e.g. -smp 5) leads to SIGP errors (the
> >> guest tries to bring these CPUs up but fails), because we don't support
> >> multiple CPUs on s390x under TCG.
> >>
> >> Let's bail out if more than 1 are specified, so we don't raise people's
> >> hope.
> >>
> >> Signed-off-by: David Hildenbrand <address@hidden>
> >> ---
> >>  hw/s390x/s390-virtio-ccw.c | 6 ++++++
> >>  1 file changed, 6 insertions(+)
> >>
> >> diff --git a/hw/s390x/s390-virtio-ccw.c b/hw/s390x/s390-virtio-ccw.c
> >> index 7754e3eaf9..eff96808c4 100644
> >> --- a/hw/s390x/s390-virtio-ccw.c
> >> +++ b/hw/s390x/s390-virtio-ccw.c
> >> @@ -23,6 +23,7 @@
> >>  #include "hw/s390x/css.h"
> >>  #include "virtio-ccw.h"
> >>  #include "qemu/config-file.h"
> >> +#include "qemu/error-report.h"
> >>  #include "s390-pci-bus.h"
> >>  #include "hw/s390x/storage-keys.h"
> >>  #include "hw/s390x/storage-attributes.h"
> >> @@ -56,6 +57,11 @@ static void s390_init_cpus(MachineState *machine)
> >>      if (machine->cpu_model == NULL) {
> >>          machine->cpu_model = s390_default_cpu_model_name();
> >>      }
> >> +    if (tcg_enabled() && max_cpus > 1) {
> >> +        error_report("Number of SMP CPUs requested (%d) exceeds max CPUs "
> >> +                     "supported by TCG (1) on s390x", max_cpus);  
> > 
> > Make this a #define, so we can just flip the switch when smp support is
> > ready?  
> 
> As an alternative: yield a warning?

If we know that this can't work, it makes sense to stop immediately, no?

> 
> >   
> >> +        exit(1);
> >> +    }
> >>  
> >>      ms->cpus = g_new0(S390CPU *, max_cpus);
> >>    
> >   
> 
>