Re: [qemu-s390x] [PATCH v2 for-2.12 08/10] s390x/tcg: implement extract-CPU-time facility

[Richard Henderson]

On 12/07/2017 08:53 AM, David Hildenbrand wrote:
> It only provides the EXTRACT CPU TIME instruction. We can reuse the stpt
> helper, which calculates the CPU timer value.
> 
> As the instruction is not privileged, but we don't have a CPU timer
> value in case of linux user, we simply fake the CPU timer to be 0.
> 
> Signed-off-by: David Hildenbrand <address@hidden>
> ---
>  target/s390x/cpu_models.c  |  1 +
>  target/s390x/insn-data.def |  2 ++
>  target/s390x/translate.c   | 36 ++++++++++++++++++++++++++++++++++++
>  3 files changed, 39 insertions(+)
> 
> diff --git a/target/s390x/cpu_models.c b/target/s390x/cpu_models.c
> index 94d24e423d..0be037eac1 100644
> --- a/target/s390x/cpu_models.c
> +++ b/target/s390x/cpu_models.c
> @@ -834,6 +834,7 @@ static void add_qemu_cpu_model_features(S390FeatBitmap 
> fbm)
>          S390_FEAT_STORE_CLOCK_FAST,
>          S390_FEAT_MOVE_WITH_OPTIONAL_SPEC,
>          S390_FEAT_ETF3_ENH,
> +        S390_FEAT_EXTRACT_CPU_TIME,
>          S390_FEAT_COMPARE_AND_SWAP_AND_STORE,
>          S390_FEAT_COMPARE_AND_SWAP_AND_STORE_2,
>          S390_FEAT_GENERAL_INSTRUCTIONS_EXT,
> diff --git a/target/s390x/insn-data.def b/target/s390x/insn-data.def
> index f7b66b0091..5e33bd27ff 100644
> --- a/target/s390x/insn-data.def
> +++ b/target/s390x/insn-data.def
> @@ -369,6 +369,8 @@
>      C(0xb24f, EAR,     RRE,   Z,   0, 0, new, r1_32, ear, 0)
>  /* EXTRACT CPU ATTRIBUTE */
>      C(0xeb4c, ECAG,    RSY_a, GIE, 0, a2, r1, 0, ecag, 0)
> +/* EXTRACT CPU TIME */
> +    C(0xc801, ECTG,    SSF,   ECT, 0, 0, 0, 0, ectg, 0)
>  /* EXTRACT FPC */
>      C(0xb38c, EFPC,    RRE,   Z,   0, 0, new, r1_32, efpc, 0)
>  /* EXTRACT PSW */
> diff --git a/target/s390x/translate.c b/target/s390x/translate.c
> index 1e4079464a..e0f55fc8e9 100644
> --- a/target/s390x/translate.c
> +++ b/target/s390x/translate.c
> @@ -3887,6 +3887,41 @@ static ExitStatus op_spm(DisasContext *s, DisasOps *o)
>      return NO_EXIT;
>  }
>  
> +static ExitStatus op_ectg(DisasContext *s, DisasOps *o)
> +{
> +    int b1 = get_field(s->fields, b1);
> +    int d1 = get_field(s->fields, d1);
> +    int b2 = get_field(s->fields, b2);
> +    int d2 = get_field(s->fields, d2);
> +    int r3 = get_field(s->fields, r3);
> +    TCGv_i64 tmp = tcg_temp_new_i64();
> +
> +    /* fetch all operands first */
> +    o->in1 = tcg_temp_new_i64();
> +    tcg_gen_addi_i64(o->in1, regs[b1], d1);
> +    o->in2 = tcg_temp_new_i64();
> +    tcg_gen_addi_i64(o->in2, regs[b2], d2);
> +    o->addr1 = get_address(s, 0, r3, 0);
> +
> +    /* load the third operand into r3 before modifying anything */
> +    tcg_gen_qemu_ld64(regs[r3], o->addr1, get_mem_index(s));
> +
> +#ifndef CONFIG_USER_ONLY
> +    /* subtract CPU timer from first operand and store in GR0 */
> +    gen_helper_stpt(tmp, cpu_env);
> +    tcg_gen_sub_i64(regs[0], o->in1, tmp);
> +#else
> +    /* we don't have a CPU timer, fake value 0 */
> +    tcg_gen_mov_i64(regs[0], o->in1);
> +#endif

It's easy enough to pass along cpu_get_host_ticks() for user-only.  Possibly
not quite right, but better than nothing.


r~