Re: [PATCH 3/6] target/riscv: Add pointer masking tb flags

[Alexey Baturo]

Hi Richard,

Thanks for the suggestion.

If it's ok to consume another bit(3 bits total) for Pointer Masking flags, I'll do it.

>so that the translator can see the true width of the address

I guess I'll need a helper to calculate the exact number of bits to shift(0, 7 or 16) based on those 2 extracted bits. Is it ok with you?

Thanks

пт, 22 дек. 2023 г. в 01:49, Richard Henderson <richard.henderson@linaro.org>:

On 12/21/23 21:40, Alexey Baturo wrote:
> From: Alexey Baturo <baturo.alexey@gmail.com>
>
> Signed-off-by: Alexey Baturo <baturo.alexey@gmail.com>
> ---
>   target/riscv/cpu.h        | 19 +++++++++++++------
>   target/riscv/cpu_helper.c |  4 ++++
>   target/riscv/translate.c  | 10 ++++++++++
>   3 files changed, 27 insertions(+), 6 deletions(-)
>
> diff --git a/target/riscv/cpu.h b/target/riscv/cpu.h
> index f49d4aa52c..2099168950 100644
> --- a/target/riscv/cpu.h
> +++ b/target/riscv/cpu.h
> @@ -390,6 +390,10 @@ struct CPUArchState {
>       target_ulong senvcfg;
>       uint64_t henvcfg;
>   #endif
> +    /* current number of masked top bits by pointer masking */
> +    target_ulong pm_pmlen;
> +    /* if pointer masking should do sign extension */
> +    bool pm_signext;
>   
>       /* Fields from here on are preserved across CPU reset. */
>       QEMUTimer *stimer; /* Internal timer for S-mode interrupt */
> @@ -538,14 +542,17 @@ FIELD(TB_FLAGS, VILL, 14, 1)
>   FIELD(TB_FLAGS, VSTART_EQ_ZERO, 15, 1)
>   /* The combination of MXL/SXL/UXL that applies to the current cpu mode. */
>   FIELD(TB_FLAGS, XL, 16, 2)
> -FIELD(TB_FLAGS, VTA, 18, 1)
> -FIELD(TB_FLAGS, VMA, 19, 1)
> +/* If pointer masking should be applied and address sign extended */
> +FIELD(TB_FLAGS, PM_ENABLED, 18, 1)

I think it would be better add the entire two bit field here, so that the translator can
see the true width of the address.  You can then use tcg_gen_{s}extract_tl to perform the
truncation.  At which point the 'target_ulong pm_pmlen' is not required.


r~

> +FIELD(TB_FLAGS, PM_SIGNEXTEND, 19, 1)
> +FIELD(TB_FLAGS, VTA, 20, 1)
> +FIELD(TB_FLAGS, VMA, 21, 1)
>   /* Native debug itrigger */
> -FIELD(TB_FLAGS, ITRIGGER, 20, 1)
> +FIELD(TB_FLAGS, ITRIGGER, 22, 1)
>   /* Virtual mode enabled */
> -FIELD(TB_FLAGS, VIRT_ENABLED, 21, 1)
> -FIELD(TB_FLAGS, PRIV, 22, 2)
> -FIELD(TB_FLAGS, AXL, 24, 2)
> +FIELD(TB_FLAGS, VIRT_ENABLED, 23, 1)
> +FIELD(TB_FLAGS, PRIV, 24, 2)
> +FIELD(TB_FLAGS, AXL, 25, 2)
>   
>   #ifdef TARGET_RISCV32
>   #define riscv_cpu_mxl(env)  ((void)(env), MXL_RV32)
> diff --git a/target/riscv/cpu_helper.c b/target/riscv/cpu_helper.c
> index a3d477d226..79cddbd930 100644
> --- a/target/riscv/cpu_helper.c
> +++ b/target/riscv/cpu_helper.c
> @@ -135,6 +135,10 @@ void cpu_get_tb_cpu_state(CPURISCVState *env, vaddr *pc,
>       flags = FIELD_DP32(flags, TB_FLAGS, VS, vs);
>       flags = FIELD_DP32(flags, TB_FLAGS, XL, env->xl);
>       flags = FIELD_DP32(flags, TB_FLAGS, AXL, cpu_address_xl(env));
> +    if (env->pm_pmlen != 0) {
> +        flags = FIELD_DP32(flags, TB_FLAGS, PM_ENABLED, 1);
> +    }
> +    flags = FIELD_DP32(flags, TB_FLAGS, PM_SIGNEXTEND, env->pm_signext);
>   
>       *pflags = flags;
>   }
> diff --git a/target/riscv/translate.c b/target/riscv/translate.c
> index 6b4b9a671c..4c0d526b58 100644
> --- a/target/riscv/translate.c
> +++ b/target/riscv/translate.c
> @@ -42,6 +42,8 @@ static TCGv cpu_gpr[32], cpu_gprh[32], cpu_pc, cpu_vl, cpu_vstart;
>   static TCGv_i64 cpu_fpr[32]; /* assume F and D extensions */
>   static TCGv load_res;
>   static TCGv load_val;
> +/* number of top masked address bits by pointer masking extension */
> +static TCGv pm_pmlen;
>   
>   /*
>    * If an operation is being performed on less than TARGET_LONG_BITS,
> @@ -103,6 +105,9 @@ typedef struct DisasContext {
>       bool vl_eq_vlmax;
>       CPUState *cs;
>       TCGv zero;
> +    /* pointer masking extension */
> +    bool pm_enabled;
> +    bool pm_signext;
>       /* Use icount trigger for native debug */
>       bool itrigger;
>       /* FRM is known to contain a valid value. */
> @@ -1176,6 +1181,8 @@ static void riscv_tr_init_disas_context(DisasContextBase *dcbase, CPUState *cs)
>       ctx->xl = FIELD_EX32(tb_flags, TB_FLAGS, XL);
>       ctx->address_xl = FIELD_EX32(tb_flags, TB_FLAGS, AXL);
>       ctx->cs = cs;
> +    ctx->pm_enabled = FIELD_EX32(tb_flags, TB_FLAGS, PM_ENABLED);
> +    ctx->pm_signext = FIELD_EX32(tb_flags, TB_FLAGS, PM_SIGNEXTEND);
>       ctx->itrigger = FIELD_EX32(tb_flags, TB_FLAGS, ITRIGGER);
>       ctx->zero = tcg_constant_tl(0);
>       ctx->virt_inst_excp = false;
> @@ -1307,4 +1314,7 @@ void riscv_translate_init(void)
>                                "load_res");
>       load_val = tcg_global_mem_new(tcg_env, offsetof(CPURISCVState, load_val),
>                                "load_val");
> +    /* Assign var with number of pointer masking masked bits to tcg global */
> +    pm_pmlen = tcg_global_mem_new(tcg_env, offsetof(CPURISCVState, pm_pmlen),
> +                                   "pmlen");
>   }