Re: [PATCH v4 10/17] target/ppc: Create helper_scv

[David Gibson]

On Mon, Mar 15, 2021 at 12:46:08PM -0600, Richard Henderson wrote:
> Perform the test against FSCR_SCV at runtime, in the helper.
> 
> This means we can remove the incorrect set against SCV in
> ppc_tr_init_disas_context and do not need to add an HFLAGS bit.
> 
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---
>  target/ppc/helper.h      |  1 +
>  target/ppc/excp_helper.c |  9 +++++++++
>  target/ppc/translate.c   | 20 +++++++-------------
>  3 files changed, 17 insertions(+), 13 deletions(-)
> 
> diff --git a/target/ppc/helper.h b/target/ppc/helper.h
> index 6a4dccf70c..513066d54d 100644
> --- a/target/ppc/helper.h
> +++ b/target/ppc/helper.h
> @@ -13,6 +13,7 @@ DEF_HELPER_1(rfci, void, env)
>  DEF_HELPER_1(rfdi, void, env)
>  DEF_HELPER_1(rfmci, void, env)
>  #if defined(TARGET_PPC64)
> +DEF_HELPER_2(scv, noreturn, env, i32)
>  DEF_HELPER_2(pminsn, void, env, i32)
>  DEF_HELPER_1(rfid, void, env)
>  DEF_HELPER_1(rfscv, void, env)
> diff --git a/target/ppc/excp_helper.c b/target/ppc/excp_helper.c
> index 85de7e6c90..5c95e0c103 100644
> --- a/target/ppc/excp_helper.c
> +++ b/target/ppc/excp_helper.c
> @@ -1130,6 +1130,15 @@ void helper_store_msr(CPUPPCState *env, target_ulong 
> val)
>  }
>  
>  #if defined(TARGET_PPC64)
> +void helper_scv(CPUPPCState *env, uint32_t lev)
> +{
> +    if (env->spr[SPR_FSCR] & (1ull << FSCR_SCV)) {
> +        raise_exception_err(env, POWERPC_EXCP_SYSCALL_VECTORED, lev);
> +    } else {
> +        raise_exception_err(env, POWERPC_EXCP_FU, FSCR_IC_SCV);
> +    }
> +}
> +
>  void helper_pminsn(CPUPPCState *env, powerpc_pm_insn_t insn)
>  {
>      CPUState *cs;
> diff --git a/target/ppc/translate.c b/target/ppc/translate.c
> index 7912495f28..d48c554290 100644
> --- a/target/ppc/translate.c
> +++ b/target/ppc/translate.c
> @@ -173,7 +173,6 @@ struct DisasContext {
>      bool vsx_enabled;
>      bool spe_enabled;
>      bool tm_enabled;
> -    bool scv_enabled;
>      bool gtse;
>      ppc_spr_t *spr_cb; /* Needed to check rights for mfspr/mtspr */
>      int singlestep_enabled;
> @@ -4081,15 +4080,16 @@ static void gen_sc(DisasContext *ctx)
>  #if !defined(CONFIG_USER_ONLY)
>  static void gen_scv(DisasContext *ctx)
>  {
> -    uint32_t lev;
> +    uint32_t lev = (ctx->opcode >> 5) & 0x7F;
>  
> -    if (unlikely(!ctx->scv_enabled)) {
> -        gen_exception_err(ctx, POWERPC_EXCP_FU, FSCR_IC_SCV);
> -        return;
> +    /* Set the PC back to the faulting instruction. */
> +    if (ctx->exception == POWERPC_EXCP_NONE) {
> +        gen_update_nip(ctx, ctx->base.pc_next - 4);
>      }

I don't quite understand this.  Don't we need the NIP to be on the scv
instruction itself for the case where we get a facility unavailable
exception, but on the next instruction if we actually take the system
call?  This appears to be unconditional.

> +    gen_helper_scv(cpu_env, tcg_constant_i32(lev));
>  
> -    lev = (ctx->opcode >> 5) & 0x7F;
> -    gen_exception_err(ctx, POWERPC_SYSCALL_VECTORED, lev);
> +    /* This need not be exact, just not POWERPC_EXCP_NONE */
> +    ctx->exception = POWERPC_SYSCALL_VECTORED;
>  }
>  #endif
>  #endif
> @@ -7907,12 +7907,6 @@ static void ppc_tr_init_disas_context(DisasContextBase 
> *dcbase, CPUState *cs)
>      ctx->spe_enabled = (hflags >> HFLAGS_SPE) & 1;
>      ctx->altivec_enabled = (hflags >> HFLAGS_VR) & 1;
>      ctx->vsx_enabled = (hflags >> HFLAGS_VSX) & 1;
> -    if ((env->flags & POWERPC_FLAG_SCV)
> -        && (env->spr[SPR_FSCR] & (1ull << FSCR_SCV))) {
> -        ctx->scv_enabled = true;
> -    } else {
> -        ctx->scv_enabled = false;
> -    }
>      ctx->tm_enabled = (hflags >> HFLAGS_TM) & 1;
>      ctx->gtse = !!(env->spr[SPR_LPCR] & LPCR_GTSE);
>  

-- 
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

signature.asc
Description: PGP signature