Re: [Qemu-devel] [PATCH v6 4/4] spapr: Implement H_JOIN

[Greg Kurz <groug@kaod.org>]

On Thu, 18 Jul 2019 13:42:14 +1000
Nicholas Piggin <npiggin@gmail.com> wrote:

> This has been useful to modify and test the Linux pseries suspend
> code but it requires modification to the guest to call it (due to
> being gated by other unimplemented features). It is not otherwise
> used by Linux yet, but work is slowly progressing there.
> 
> Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
> ---

Reviewed-by: Greg Kurz <groug@kaod.org>

> Changes since v5:
> - Fix prod bit semantics.
> - Factor out the h_confer_self common code
> 
> Changes since v4:
> - Style
> 
>  hw/ppc/spapr.c       |  1 +
>  hw/ppc/spapr_hcall.c | 74 ++++++++++++++++++++++++++++++++++++--------
>  2 files changed, 62 insertions(+), 13 deletions(-)
> 
> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> index 68341c128d..00f7735a31 100644
> --- a/hw/ppc/spapr.c
> +++ b/hw/ppc/spapr.c
> @@ -1066,6 +1066,7 @@ static void spapr_dt_rtas(SpaprMachineState *spapr, void *fdt)
>      add_str(hypertas, "hcall-tce");
>      add_str(hypertas, "hcall-vio");
>      add_str(hypertas, "hcall-splpar");
> +    add_str(hypertas, "hcall-join");
>      add_str(hypertas, "hcall-bulk");
>      add_str(hypertas, "hcall-set-mode");
>      add_str(hypertas, "hcall-sprg0");
> diff --git a/hw/ppc/spapr_hcall.c b/hw/ppc/spapr_hcall.c
> index 7c659dc75c..9b72ea8b68 100644
> --- a/hw/ppc/spapr_hcall.c
> +++ b/hw/ppc/spapr_hcall.c
> @@ -1069,6 +1069,62 @@ static target_ulong h_cede(PowerPCCPU *cpu, SpaprMachineState *spapr,
>      return H_SUCCESS;
>  }
>  
> +/*
> + * Confer to self, aka join. Cede could use the same pattern as well, if
> + * EXCP_HLT can be changed to ECXP_HALTED.
> + */
> +static target_ulong h_confer_self(PowerPCCPU *cpu)
> +{
> +    CPUState *cs = CPU(cpu);
> +    SpaprCpuState *spapr_cpu = spapr_cpu_state(cpu);
> +
> +    if (spapr_cpu->prod) {
> +        spapr_cpu->prod = false;
> +        return H_SUCCESS;
> +    }
> +    cs->halted = 1;
> +    cs->exception_index = EXCP_HALTED;
> +    cs->exit_request = 1;
> +
> +    return H_SUCCESS;
> +}
> +
> +static target_ulong h_join(PowerPCCPU *cpu, SpaprMachineState *spapr,
> +                           target_ulong opcode, target_ulong *args)
> +{
> +    CPUPPCState *env = &cpu->env;
> +    CPUState *cs;
> +    bool last_unjoined = true;
> +
> +    if (env->msr & (1ULL << MSR_EE)) {
> +        return H_BAD_MODE;
> +    }
> +
> +    /*
> +     * Must not join the last CPU running. Interestingly, no such restriction
> +     * for H_CONFER-to-self, but that is probably not intended to be used
> +     * when H_JOIN is available.
> +     */
> +    CPU_FOREACH(cs) {
> +        PowerPCCPU *c = POWERPC_CPU(cs);
> +        CPUPPCState *e = &c->env;
> +        if (c == cpu) {
> +            continue;
> +        }
> +
> +        /* Don't have a way to indicate joined, so use halted && MSR[EE]=0 */
> +        if (!cs->halted || (e->msr & (1ULL << MSR_EE))) {
> +            last_unjoined = false;
> +            break;
> +        }
> +    }
> +    if (last_unjoined) {
> +        return H_CONTINUE;
> +    }
> +
> +    return h_confer_self(cpu);
> +}
> +
>  static target_ulong h_confer(PowerPCCPU *cpu, SpaprMachineState *spapr,
>                             target_ulong opcode, target_ulong *args)
>  {
> @@ -1089,26 +1145,15 @@ static target_ulong h_confer(PowerPCCPU *cpu, SpaprMachineState *spapr,
>              return H_PARAMETER;
>          }
>  
> -        spapr_cpu = spapr_cpu_state(target_cpu);
> -
>          /*
>           * target == self is a special case, we wait until prodded, without
>           * dispatch counter check.
>           */
>          if (cpu == target_cpu) {
> -            if (spapr_cpu->prod) {
> -                spapr_cpu->prod = false;
> -
> -                return H_SUCCESS;
> -            }
> -
> -            cs->halted = 1;
> -            cs->exception_index = EXCP_HALTED;
> -            cs->exit_request = 1;
> -
> -            return H_SUCCESS;
> +            return h_confer_self(cpu);
>          }
>  
> +        spapr_cpu = spapr_cpu_state(target_cpu);
>          if (!spapr_cpu->vpa_addr || ((dispatch & 1) == 0)) {
>              return H_SUCCESS;
>          }
> @@ -1981,6 +2026,9 @@ static void hypercall_register_types(void)
>      spapr_register_hypercall(H_CONFER, h_confer);
>      spapr_register_hypercall(H_PROD, h_prod);
>  
> +    /* hcall-join */
> +    spapr_register_hypercall(H_JOIN, h_join);
> +
>      spapr_register_hypercall(H_SIGNAL_SYS_RESET, h_signal_sys_reset);
>  
>      /* processor register resource access h-calls */