Re: [Qemu-ppc] [RFC] powernv: CPU compatibility modes don't make sense for powernv

[Cédric Le Goater]

On 10/28/2016 04:05 AM, David Gibson wrote:
> powernv has some code (derived from the spapr equivalent) used in device
> tree generation which depends on the CPU's compatibility mode / logical
> PVR.  However, compatibility modes don't make sense on powernv - at least
> not as a property controlled by the host - because the guest in powernv
> has full hypervisor level access to the virtual system, and so owns the
> PCR (Processor Compatibility Register) which implements compatiblity modes.
> 
> Signed-off-by: David Gibson <address@hidden>
> ---
>  hw/ppc/pnv.c | 6 +-----
>  1 file changed, 1 insertion(+), 5 deletions(-)
> 
> Hi Cédric, I'd appreciate it if you can double check my reasoning
> here.  This patch gets powernv out of the way of a bunch of
> compatibility mode cleanups I have in the works.

It makes perfect sense. The "cpu-version" property is for PAPR, not for OPAL.
hostboot and skiboot put SPR_PVR in this property. 

I will be careful using 'CPU_CORE(pc)->nr_threads' in the ICP patches also. 

Reviewed-by: Cédric Le Goater <address@hidden>

Thanks,

C.


> 
> diff --git a/hw/ppc/pnv.c b/hw/ppc/pnv.c
> index 82276e0..6af3424 100644
> --- a/hw/ppc/pnv.c
> +++ b/hw/ppc/pnv.c
> @@ -110,7 +110,7 @@ static void powernv_create_core_node(PnvChip *chip, 
> PnvCore *pc, void *fdt)
>      CPUState *cs = CPU(DEVICE(pc->threads));
>      DeviceClass *dc = DEVICE_GET_CLASS(cs);
>      PowerPCCPU *cpu = POWERPC_CPU(cs);
> -    int smt_threads = ppc_get_compat_smt_threads(cpu);
> +    int smt_threads = CPU_CORE(pc)->nr_threads;
>      CPUPPCState *env = &cpu->env;
>      PowerPCCPUClass *pcc = POWERPC_CPU_GET_CLASS(cs);
>      uint32_t servers_prop[smt_threads];
> @@ -206,10 +206,6 @@ static void powernv_create_core_node(PnvChip *chip, 
> PnvCore *pc, void *fdt)
>      _FDT((fdt_setprop(fdt, offset, "ibm,pa-features",
>                         pa_features, sizeof(pa_features))));
>  
> -    if (cpu->cpu_version) {
> -        _FDT((fdt_setprop_cell(fdt, offset, "cpu-version", 
> cpu->cpu_version)));
> -    }
> -
>      /* Build interrupt servers properties */
>      for (i = 0; i < smt_threads; i++) {
>          servers_prop[i] = cpu_to_be32(pc->pir + i);
>