Re: [Qemu-devel] [PATCH] hw/ppc/spapr: Use POWER8 by default for the pseries-2.8 machine

[David Gibson <david@gibson.dropbear.id.au>]

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On Tue, Oct 04, 2016 at 02:55:44PM +0200, Thomas Huth wrote:
> A couple of distributors are compiling their distributions
> with "-mcpu=power8" for ppc64le these days, so the user sooner
> or later runs into a crash there when not explicitely specifying
> the "-cpu POWER8" option to QEMU. Due to this reason, the linux-user
> target already switched to POWER8 by default a while ago (see commit
> de3f1b98410e0d5b406a0df3a48547b559d18602). Since the softmmu target
> of course has the same problem, we should switch there to POWER8
> by default for the newer machine types, too.
> 
> Buglink: https://bugzilla.redhat.com/show_bug.cgi?id=1357808
> Signed-off-by: Thomas Huth <thuth@redhat.com>

Sounds good, one detail..

> ---
>  Note: This patch should be applied on top of David's ppc-for-2.8
>  tree, since the pseries-2.8 machine has just been added there
>  recently.
> 
>  hw/ppc/spapr.c         | 11 ++++++++++-
>  include/hw/ppc/spapr.h |  1 +
>  2 files changed, 11 insertions(+), 1 deletion(-)
> 
> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> index 63b6a0d..799bcff 100644
> --- a/hw/ppc/spapr.c
> +++ b/hw/ppc/spapr.c
> @@ -1775,7 +1775,13 @@ static void ppc_spapr_init(MachineState *machine)
>  
>      /* init CPUs */
>      if (machine->cpu_model == NULL) {
> -        machine->cpu_model = kvm_enabled() ? "host" : "POWER7";
> +        if (kvm_enabled()) {
> +            machine->cpu_model = "host";
> +        } else if (smc->tcg_default_cpu) {
> +            machine->cpu_model = smc->tcg_default_cpu;
> +        } else {
> +            machine->cpu_model = "POWER8";
> +        }

You can avoid the last if branch if you initialize tcg_default_cpu to
POWER8 in spapr_machine_class_init().

>      }
>  
>      ppc_cpu_parse_features(machine->cpu_model);
> @@ -2478,7 +2484,10 @@ static void spapr_machine_2_7_instance_options(MachineState *machine)
>  
>  static void spapr_machine_2_7_class_options(MachineClass *mc)
>  {
> +    sPAPRMachineClass *smc = SPAPR_MACHINE_CLASS(mc);
> +
>      spapr_machine_2_8_class_options(mc);
> +    smc->tcg_default_cpu = "POWER7";
>      SET_MACHINE_COMPAT(mc, SPAPR_COMPAT_2_7);
>  }
>  
> diff --git a/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h
> index 6289d50..39dadaa 100644
> --- a/include/hw/ppc/spapr.h
> +++ b/include/hw/ppc/spapr.h
> @@ -39,6 +39,7 @@ struct sPAPRMachineClass {
>      /*< public >*/
>      bool dr_lmb_enabled;       /* enable dynamic-reconfig/hotplug of LMBs */
>      bool use_ohci_by_default;  /* use USB-OHCI instead of XHCI */
> +    const char *tcg_default_cpu; /* which (TCG) CPU to simulate by default */
>  };
>  
>  /**

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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