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Date: Tue, 12 Sep 2017 14:43:30 +0200
From: Igor Mammedov <imammedo@redhat.com>
Message-ID: <20170912144330.3f07b30b@nial.brq.redhat.com>
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	<20170911152150.12535-12-david@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH v4 11/21] s390x: allow only 1 CPU with TCG
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To: David Hildenbrand <david@redhat.com>
Cc: qemu-devel@nongnu.org, Matthew Rosato <mjrosato@linux.vnet.ibm.com>, thuth@redhat.com, Eduardo Habkost <ehabkost@redhat.com>, cohuck@redhat.com, Richard Henderson <richard.henderson@linaro.org>, Alexander Graf <agraf@suse.de>, Markus Armbruster <armbru@redhat.com>, borntraeger@de.ibm.com, Paolo Bonzini <pbonzini@redhat.com>

On Mon, 11 Sep 2017 17:21:40 +0200
David Hildenbrand <david@redhat.com> 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 is specified, so we don't raise people's
> hope. Make it a define, so we can easily bump it up later.
> 
> Tested-by: Matthew Rosato <mjrosato@linux.vnet.ibm.com>
> Signed-off-by: David Hildenbrand <david@redhat.com>
> ---
>  hw/s390x/s390-virtio-ccw.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/hw/s390x/s390-virtio-ccw.c b/hw/s390x/s390-virtio-ccw.c
> index f67b4b5d58..f1198b2745 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"
> @@ -47,6 +48,8 @@ S390CPU *s390_cpu_addr2state(uint16_t cpu_addr)
>      return cpu_states[cpu_addr];
>  }
>  
> +/* #define S390_TCG_SMP_SUPPORT */
I'd drop define and ifdef for something that doesn't exists

>  static void s390_init_cpus(MachineState *machine)
>  {
>      int i;
> @@ -55,6 +58,13 @@ static void s390_init_cpus(MachineState *machine)
>      if (machine->cpu_model == NULL) {
>          machine->cpu_model = s390_default_cpu_model_name();
>      }
> +#ifndef S390_TCG_SMP_SUPPORT
> +    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);
> +        exit(1);
> +    }
> +#endif
>  
>      cpu_states = g_new0(S390CPU *, max_cpus);
>