Re: [Qemu-devel] [PATCH 08/19] target/ppc: Fix nip on power management instructions

[David Gibson]

On Mon, Jan 28, 2019 at 10:46:14AM +0100, Cédric Le Goater wrote:
> From: Benjamin Herrenschmidt <address@hidden>
> 
> Those instructions currently raise an exception from within
> the helper. This tends to result in a bogus nip value in
> the env context (typically the beginning of the TB). Such
> a helper needs a gen_update_nip() first.
> 
> This fixes it with a different approach which is to throw
> the exception from translate.c instead of the helper using
> gen_exception_nip() which does the right thing.
> 
> Signed-off-by: Benjamin Herrenschmidt <address@hidden>
> Signed-off-by: Cédric Le Goater <address@hidden>
> ---
>  target/ppc/excp_helper.c |  1 -
>  target/ppc/translate.c   | 12 ++++++++----
>  2 files changed, 8 insertions(+), 5 deletions(-)
> 
> diff --git a/target/ppc/excp_helper.c b/target/ppc/excp_helper.c
> index 751d759fcc1d..8407e0ade938 100644
> --- a/target/ppc/excp_helper.c
> +++ b/target/ppc/excp_helper.c
> @@ -958,7 +958,6 @@ void helper_pminsn(CPUPPCState *env, powerpc_pm_insn_t 
> insn)
>       * but this doesn't seem to be a problem.
>       */
>      env->msr |= (1ull << MSR_EE);
> -    raise_exception(env, EXCP_HLT);
>  }
>  #endif /* defined(TARGET_PPC64) */
>  
> diff --git a/target/ppc/translate.c b/target/ppc/translate.c
> index 7d40a1fbe6bd..55281a8975e0 100644
> --- a/target/ppc/translate.c
> +++ b/target/ppc/translate.c
> @@ -3571,7 +3571,8 @@ static void gen_doze(DisasContext *ctx)
>      t = tcg_const_i32(PPC_PM_DOZE);
>      gen_helper_pminsn(cpu_env, t);
>      tcg_temp_free_i32(t);
> -    gen_stop_exception(ctx);
> +    /* Stop translation, as the CPU is supposed to sleep from now */
> +    gen_exception_nip(ctx, EXCP_HLT, ctx->base.pc_next);

IIUC this also changes from EXCP_STOP to EXCP_HLT, is that intentional?

>  #endif /* defined(CONFIG_USER_ONLY) */
>  }
>  
> @@ -3586,7 +3587,8 @@ static void gen_nap(DisasContext *ctx)
>      t = tcg_const_i32(PPC_PM_NAP);
>      gen_helper_pminsn(cpu_env, t);
>      tcg_temp_free_i32(t);
> -    gen_stop_exception(ctx);
> +    /* 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) */
>  }
>  
> @@ -3606,7 +3608,8 @@ static void gen_sleep(DisasContext *ctx)
>      t = tcg_const_i32(PPC_PM_SLEEP);
>      gen_helper_pminsn(cpu_env, t);
>      tcg_temp_free_i32(t);
> -    gen_stop_exception(ctx);
> +    /* 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) */
>  }
>  
> @@ -3621,7 +3624,8 @@ static void gen_rvwinkle(DisasContext *ctx)
>      t = tcg_const_i32(PPC_PM_RVWINKLE);
>      gen_helper_pminsn(cpu_env, t);
>      tcg_temp_free_i32(t);
> -    gen_stop_exception(ctx);
> +    /* 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) */
>  }
>  #endif /* #if defined(TARGET_PPC64) */

-- 
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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