Re: [Qemu-devel] [PATCH 10/19] target/ppc: Fix support for "STOP light" states on POWER9

[David Gibson]

On Mon, Jan 28, 2019 at 10:46:16AM +0100, Cédric Le Goater wrote:
> From: Benjamin Herrenschmidt <address@hidden>
> 
> STOP must act differently based on PSSCR:EC on POWER9. When set, it
> acts like the P7/P8 power management instructions and wake up at 0x100
> based on the wakeup conditions in LPCR.
> 
> When PSSCR:EC is clear however it will wakeup at the next instruction
> after STOP (if EE is clear) or take the corresponding interrupts (if
> EE is set).
> 
> Signed-off-by: Benjamin Herrenschmidt <address@hidden>
> Signed-off-by: Cédric Le Goater <address@hidden>

Reviewed-by: David Gibson <address@hidden>

> ---
>  target/ppc/cpu-qom.h            |  1 +
>  target/ppc/cpu.h                | 12 +++++++++---
>  target/ppc/excp_helper.c        |  8 ++++++--
>  target/ppc/translate.c          | 13 ++++++++++++-
>  target/ppc/translate_init.inc.c |  7 +++++++
>  5 files changed, 35 insertions(+), 6 deletions(-)
> 
> diff --git a/target/ppc/cpu-qom.h b/target/ppc/cpu-qom.h
> index 4ea67692e2a6..7c54093a7122 100644
> --- a/target/ppc/cpu-qom.h
> +++ b/target/ppc/cpu-qom.h
> @@ -122,6 +122,7 @@ typedef enum {
>      PPC_PM_NAP,
>      PPC_PM_SLEEP,
>      PPC_PM_RVWINKLE,
> +    PPC_PM_STOP,
>  } powerpc_pm_insn_t;
>  
>  
> /*****************************************************************************/
> diff --git a/target/ppc/cpu.h b/target/ppc/cpu.h
> index 2c22292e7f41..7ff65c804b57 100644
> --- a/target/ppc/cpu.h
> +++ b/target/ppc/cpu.h
> @@ -413,6 +413,10 @@ struct ppc_slb_t {
>  #define LPCR_HVICE        PPC_BIT(62) /* HV Virtualisation Int Enable */
>  #define LPCR_HDICE        PPC_BIT(63)
>  
> +/* PSSCR bits */
> +#define PSSCR_ESL         PPC_BIT(42) /* Enable State Loss */
> +#define PSSCR_EC          PPC_BIT(43) /* Exit Criterion */
> +
>  #define msr_sf   ((env->msr >> MSR_SF)   & 1)
>  #define msr_isf  ((env->msr >> MSR_ISF)  & 1)
>  #define msr_shv  ((env->msr >> MSR_SHV)  & 1)
> @@ -1109,9 +1113,11 @@ struct CPUPPCState {
>       * instructions and SPRs are diallowed if MSR:HV is 0
>       */
>      bool has_hv_mode;
> -    /* On P7/P8, set when in PM state, we need to handle resume
> -     * in a special way (such as routing some resume causes to
> -     * 0x100), so flag this here.
> +
> +    /*
> +     * On P7/P8/P9, set when in PM state, we need to handle resume in
> +     * a special way (such as routing some resume causes to 0x100), so
> +     * flag this here.
>       */
>      bool in_pm_state;
>  #endif
> diff --git a/target/ppc/excp_helper.c b/target/ppc/excp_helper.c
> index 7c7c8d1b9dc6..97503193ef43 100644
> --- a/target/ppc/excp_helper.c
> +++ b/target/ppc/excp_helper.c
> @@ -97,7 +97,10 @@ static inline void powerpc_excp(PowerPCCPU *cpu, int 
> excp_model, int excp)
>      asrr0 = -1;
>      asrr1 = -1;
>  
> -    /* check for special resume at 0x100 from doze/nap/sleep/winkle on P7/P8 
> */
> +    /*
> +     * check for special resume at 0x100 from doze/nap/sleep/winkle on
> +     * P7/P8/P9
> +     */
>      if (env->in_pm_state) {
>          env->in_pm_state = false;
>  
> @@ -960,7 +963,8 @@ void helper_pminsn(CPUPPCState *env, powerpc_pm_insn_t 
> insn)
>      env->pending_interrupts &= ~(1 << PPC_INTERRUPT_HDECR);
>  
>      /* Condition for waking up at 0x100 */
> -    env->in_pm_state = true;
> +    env->in_pm_state = (insn != PPC_PM_STOP) ||
> +        (env->spr[SPR_PSSCR] & PSSCR_EC);
>  }
>  #endif /* defined(TARGET_PPC64) */
>  
> diff --git a/target/ppc/translate.c b/target/ppc/translate.c
> index 55281a8975e0..07bedbb8f1ce 100644
> --- a/target/ppc/translate.c
> +++ b/target/ppc/translate.c
> @@ -3594,7 +3594,18 @@ static void gen_nap(DisasContext *ctx)
>  
>  static void gen_stop(DisasContext *ctx)
>  {
> -    gen_nap(ctx);
> +#if defined(CONFIG_USER_ONLY)
> +    GEN_PRIV;
> +#else
> +    TCGv_i32 t;
> +
> +    CHK_HV;
> +    t = tcg_const_i32(PPC_PM_STOP);
> +    gen_helper_pminsn(cpu_env, t);
> +    tcg_temp_free_i32(t);
> +    /* Stop translation, as the CPU is supposed to sleep from now */
> +    gen_exception_nip(ctx, EXCP_HLT, ctx->base.pc_next);
> +#endif /* defined(CONFIG_USER_ONLY) */
>  }
>  
>  static void gen_sleep(DisasContext *ctx)
> diff --git a/target/ppc/translate_init.inc.c b/target/ppc/translate_init.inc.c
> index 59e0b8676236..076d94f45755 100644
> --- a/target/ppc/translate_init.inc.c
> +++ b/target/ppc/translate_init.inc.c
> @@ -8801,9 +8801,16 @@ static bool cpu_has_work_POWER9(CPUState *cs)
>      CPUPPCState *env = &cpu->env;
>  
>      if (cs->halted) {
> +        uint64_t psscr = env->spr[SPR_PSSCR];
> +
>          if (!(cs->interrupt_request & CPU_INTERRUPT_HARD)) {
>              return false;
>          }
> +
> +        /* If EC is clear, just return true on any pending interrupt */
> +        if (!(psscr & PSSCR_EC)) {
> +            return true;
> +        }
>          /* External Exception */
>          if ((env->pending_interrupts & (1u << PPC_INTERRUPT_EXT)) &&
>              (env->spr[SPR_LPCR] & LPCR_EEE)) {

-- 
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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