[18/18] ppc/pnv: Add an LPAR per core machine option

Recent POWER CPUs can operate in "LPAR per core" or "LPAR per thread"
modes. In per-core mode, some SPRs and IPI doorbells are shared between
threads in a core. In per-thread mode, supervisor and user state is
not shared between threads.

OpenPOWER systems after POWER8 use LPAR per thread mode, and it is
required for KVM. Enterprise systems use LPAR per core mode, as they
partition the machine by core.

Implement a lpar-per-core machine option for powernv machines. This
is fixed true for POWER8 machines, and defaults off for P9 and P10.

With this change, powernv8 SMT now works sufficiently to run Linux,
including KVM.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
---
 include/hw/ppc/pnv.h      |  1 +
 include/hw/ppc/pnv_core.h |  1 +
 hw/ppc/pnv.c              | 29 +++++++++++++++++++++++++++++
 hw/ppc/pnv_core.c         |  8 ++++++++
 target/ppc/cpu_init.c     |  3 ++-
 5 files changed, 41 insertions(+), 1 deletion(-)

On 7/11/24 16:18, Nicholas Piggin wrote:
> Recent POWER CPUs can operate in "LPAR per core" or "LPAR per thread"
> modes. In per-core mode, some SPRs and IPI doorbells are shared between
> threads in a core. In per-thread mode, supervisor and user state is
> not shared between threads.
> 
> OpenPOWER systems after POWER8 use LPAR per thread mode, and it is
> required for KVM. Enterprise systems use LPAR per core mode, as they
> partition the machine by core.
> 
> Implement a lpar-per-core machine option for powernv machines. This
> is fixed true for POWER8 machines, and defaults off for P9 and P10.
> 
> With this change, powernv8 SMT now works sufficiently to run Linux,
> including KVM.
> 
> Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
> ---
>   include/hw/ppc/pnv.h      |  1 +
>   include/hw/ppc/pnv_core.h |  1 +
>   hw/ppc/pnv.c              | 29 +++++++++++++++++++++++++++++
>   hw/ppc/pnv_core.c         |  8 ++++++++
>   target/ppc/cpu_init.c     |  3 ++-
>   5 files changed, 41 insertions(+), 1 deletion(-)
> 
> diff --git a/include/hw/ppc/pnv.h b/include/hw/ppc/pnv.h
> index b7858d310d..73f0d72f55 100644
> --- a/include/hw/ppc/pnv.h
> +++ b/include/hw/ppc/pnv.h
> @@ -104,6 +104,7 @@ struct PnvMachineState {
>       hwaddr       fw_load_addr;
>   
>       bool         big_core;
> +    bool         lpar_per_core;
>   };
>   
>   PnvChip *pnv_get_chip(PnvMachineState *pnv, uint32_t chip_id);
> diff --git a/include/hw/ppc/pnv_core.h b/include/hw/ppc/pnv_core.h
> index 1de79a818e..d8afb4f95f 100644
> --- a/include/hw/ppc/pnv_core.h
> +++ b/include/hw/ppc/pnv_core.h
> @@ -57,6 +57,7 @@ struct PnvCore {
>       /*< public >*/
>       PowerPCCPU **threads;
>       bool big_core;
> +    bool lpar_per_core;
>       uint32_t pir;
>       uint32_t hwid;
>       uint64_t hrmor;
> diff --git a/hw/ppc/pnv.c b/hw/ppc/pnv.c
> index 71b2b3806c..f9a05fa0ff 100644
> --- a/hw/ppc/pnv.c
> +++ b/hw/ppc/pnv.c
> @@ -1026,6 +1026,11 @@ static void pnv_init(MachineState *machine)
>           exit(1);
>       }
>   
> +    if (!object_property_find(OBJECT(pnv), "lpar-per-core")) {
> +        /* POWER8 is always in lpar-per-core mode */
> +        pnv->lpar_per_core = true;
> +    }

yep.

A better alternative would be to introduce a PnvChipClass::lpar_per_core
attribute (set to true for POWER8) and OR PnvChipClass::lpar_per_core
with pnv->lpar_per_core to set the "lpar-per-core" property of PnvCore
in pnv_chip_core_realize().


Thanks,

C.



>       pnv->num_chips =
>           machine->smp.max_cpus / (machine->smp.cores * machine->smp.threads);
>   
> @@ -2589,6 +2594,18 @@ static void pnv_machine_set_big_core(Object *obj, bool value, Error **errp)
>       pnv->big_core = value;
>   }
>   
> +static bool pnv_machine_get_1lpar(Object *obj, Error **errp)
> +{
> +    PnvMachineState *pnv = PNV_MACHINE(obj);
> +    return pnv->lpar_per_core;
> +}
> +
> +static void pnv_machine_set_1lpar(Object *obj, bool value, Error **errp)
> +{
> +    PnvMachineState *pnv = PNV_MACHINE(obj);
> +    pnv->lpar_per_core = value;
> +}
> +
>   static bool pnv_machine_get_hb(Object *obj, Error **errp)
>   {
>       PnvMachineState *pnv = PNV_MACHINE(obj);
> @@ -2662,6 +2679,12 @@ static void pnv_machine_power9_class_init(ObjectClass *oc, void *data)
>                                      pnv_machine_set_big_core);
>       object_class_property_set_description(oc, "big-core",
>                                 "Use big-core (aka fused-core) mode");
> +
> +    object_class_property_add_bool(oc, "lpar-per-core",
> +                                   pnv_machine_get_1lpar,
> +                                   pnv_machine_set_1lpar);
> +    object_class_property_set_description(oc, "lpar-per-core",
> +                              "Use 1 LPAR per core mode");
>   }
>   
>   static void pnv_machine_p10_common_class_init(ObjectClass *oc, void *data)
> @@ -2709,6 +2732,12 @@ static void pnv_machine_power10_class_init(ObjectClass *oc, void *data)
>                                      pnv_machine_set_big_core);
>       object_class_property_set_description(oc, "big-core",
>                                 "Use big-core (aka fused-core) mode");
> +
> +    object_class_property_add_bool(oc, "lpar-per-core",
> +                                   pnv_machine_get_1lpar,
> +                                   pnv_machine_set_1lpar);
> +    object_class_property_set_description(oc, "lpar-per-core",
> +                              "Use 1 LPAR per core mode");
>   }
>   
>   static void pnv_machine_p10_rainier_class_init(ObjectClass *oc, void *data)
> diff --git a/hw/ppc/pnv_core.c b/hw/ppc/pnv_core.c
> index a685a5dc1b..5a6fcb6edc 100644
> --- a/hw/ppc/pnv_core.c
> +++ b/hw/ppc/pnv_core.c
> @@ -208,6 +208,9 @@ static uint64_t pnv_core_power10_xscom_read(void *opaque, hwaddr addr,
>                   val |= PPC_BIT(56 + i);
>               }
>           }
> +        if (pc->lpar_per_core) {
> +            val |= PPC_BIT(62);
> +        }
>           break;
>       case PNV10_XSCOM_EC_CORE_THREAD_INFO:
>           break;
> @@ -320,6 +323,10 @@ static void pnv_core_cpu_realize(PnvCore *pc, PowerPCCPU *cpu, Error **errp,
>           env->core_index = core_hwid;
>       }
>   
> +    if (pc->lpar_per_core) {
> +        cpu_ppc_set_1lpar(cpu);
> +    }
> +
>       /* Set time-base frequency to 512 MHz */
>       cpu_ppc_tb_init(env, PNV_TIMEBASE_FREQ);
>   }
> @@ -352,6 +359,7 @@ static void pnv_core_realize(DeviceState *dev, Error **errp)
>   
>       pc->big_core = pnv->big_core;
>       pc->tod_state.big_core_quirk = pmc->quirk_tb_big_core;
> +    pc->lpar_per_core = pc->chip->pnv_machine->lpar_per_core;
>   
>       pc->threads = g_new(PowerPCCPU *, cc->nr_threads);
>       for (i = 0; i < cc->nr_threads; i++) {
> diff --git a/target/ppc/cpu_init.c b/target/ppc/cpu_init.c
> index 9349001b76..0fc83d5cc2 100644
> --- a/target/ppc/cpu_init.c
> +++ b/target/ppc/cpu_init.c
> @@ -6785,7 +6785,8 @@ void cpu_ppc_set_1lpar(PowerPCCPU *cpu)
>   
>       /*
>        * pseries SMT means "LPAR per core" mode, e.g., msgsndp is usable
> -     * between threads.
> +     * between threads. powernv be in either mode, and it mostly affects
> +     * supervisor visible registers and instructions.
>        */
>       if (env->flags & POWERPC_FLAG_SMT) {
>           env->flags |= POWERPC_FLAG_SMT_1LPAR;