Re: [PATCH] ppc/spapr: fix default cpu for pre-10.0 machines.

[Daniel P . Berrangé]

On Wed, Mar 12, 2025 at 11:28:04AM +0530, Harsh Prateek Bora wrote:
> When POWER10 CPU was made as default, we missed keeping POWER9 as
> default for older pseries releases (pre-10.0) at that time.
> This caused breakge in default cpu evaluation for older pseries
> machines and hence this fix.
> 
> Fixes: 51113013f3 ("ppc/spapr: change pseries machine default to POWER10 CPU")
> Signed-off-by: Harsh Prateek Bora <harshpb@linux.ibm.com>
> ---
>  hw/ppc/spapr.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> index c15340a58d..b31a91e2e2 100644
> --- a/hw/ppc/spapr.c
> +++ b/hw/ppc/spapr.c
> @@ -4748,6 +4748,7 @@ static void 
> spapr_machine_9_2_class_options(MachineClass *mc)
>  {
>      spapr_machine_10_0_class_options(mc);
>      compat_props_add(mc->compat_props, hw_compat_9_2, hw_compat_9_2_len);
> +    mc->default_cpu_type = POWERPC_CPU_TYPE_NAME("power9_v2.2");
>  }

This doesn't make sense.

AFAICT, the commit 51113013f3 was introduced in the QEMU 9.0.0 release,
so it is correct that every machine from pseries-9.0 and newer had the
POWER10 CPU model.

What broke were the machines that already existed prior to the
9.0.0 release, whose default CPU got changed.  IOW, the pseries-8.2
and earlier machines.


With regards,
Daniel
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