Re: [PATCH v3] target/riscv: Set mstatus_hs.[SD|FS] bits if Clean and V=1 in mark_fs_dirty()

[Alistair Francis]

On Tue, Sep 21, 2021 at 12:03 PM <frank.chang@sifive.com> wrote:
>
> From: Frank Chang <frank.chang@sifive.com>
>
> When V=1, both vsstauts.FS and HS-level sstatus.FS are in effect.
> Modifying the floating-point state when V=1 causes both fields to
> be set to 3 (Dirty).
>
> However, it's possible that HS-level sstatus.FS is Clean and VS-level
> vsstatus.FS is Dirty at the time mark_fs_dirty() is called when V=1.
> We can't early return for this case because we still need to set
> sstatus.FS to Dirty according to spec.
>
> Signed-off-by: Frank Chang <frank.chang@sifive.com>
> Reviewed-by: Vincent Chen <vincent.chen@sifive.com>
> Tested-by: Vincent Chen <vincent.chen@sifive.com>
> Reviewed-by: Richard Henderson <richard.henderson@linaro.org>

Reviewed-by: Alistair Francis <alistair.francis@wdc.com>

Alistair

> ---
>  target/riscv/cpu.h       |  4 ++++
>  target/riscv/translate.c | 30 +++++++++++++++++-------------
>  2 files changed, 21 insertions(+), 13 deletions(-)
>
> diff --git a/target/riscv/cpu.h b/target/riscv/cpu.h
> index e735e53e26c..bef7c551646 100644
> --- a/target/riscv/cpu.h
> +++ b/target/riscv/cpu.h
> @@ -394,6 +394,7 @@ FIELD(TB_FLAGS, SEW, 5, 3)
>  FIELD(TB_FLAGS, VILL, 8, 1)
>  /* Is a Hypervisor instruction load/store allowed? */
>  FIELD(TB_FLAGS, HLSX, 9, 1)
> +FIELD(TB_FLAGS, MSTATUS_HS_FS, 10, 2)
>
>  bool riscv_cpu_is_32bit(CPURISCVState *env);
>
> @@ -450,6 +451,9 @@ static inline void cpu_get_tb_cpu_state(CPURISCVState 
> *env, target_ulong *pc,
>                  get_field(env->hstatus, HSTATUS_HU))) {
>              flags = FIELD_DP32(flags, TB_FLAGS, HLSX, 1);
>          }
> +
> +        flags = FIELD_DP32(flags, TB_FLAGS, MSTATUS_HS_FS,
> +                           get_field(env->mstatus_hs, MSTATUS_FS));
>      }
>  #endif
>
> diff --git a/target/riscv/translate.c b/target/riscv/translate.c
> index 74b33fa3c90..6be22347426 100644
> --- a/target/riscv/translate.c
> +++ b/target/riscv/translate.c
> @@ -58,6 +58,7 @@ typedef struct DisasContext {
>      target_ulong misa;
>      uint32_t opcode;
>      uint32_t mstatus_fs;
> +    uint32_t mstatus_hs_fs;
>      uint32_t mem_idx;
>      /* Remember the rounding mode encoded in the previous fp instruction,
>         which we have already installed into env->fp_status.  Or -1 for
> @@ -280,27 +281,29 @@ static void gen_jal(DisasContext *ctx, int rd, 
> target_ulong imm)
>  static void mark_fs_dirty(DisasContext *ctx)
>  {
>      TCGv tmp;
> -    target_ulong sd;
> +    target_ulong sd = is_32bit(ctx) ? MSTATUS32_SD : MSTATUS64_SD;
>
> -    if (ctx->mstatus_fs == MSTATUS_FS) {
> -        return;
> -    }
> -    /* Remember the state change for the rest of the TB.  */
> -    ctx->mstatus_fs = MSTATUS_FS;
> +    if (ctx->mstatus_fs != MSTATUS_FS) {
> +        /* Remember the state change for the rest of the TB. */
> +        ctx->mstatus_fs = MSTATUS_FS;
>
> -    tmp = tcg_temp_new();
> -    sd = is_32bit(ctx) ? MSTATUS32_SD : MSTATUS64_SD;
> +        tmp = tcg_temp_new();
> +        tcg_gen_ld_tl(tmp, cpu_env, offsetof(CPURISCVState, mstatus));
> +        tcg_gen_ori_tl(tmp, tmp, MSTATUS_FS | sd);
> +        tcg_gen_st_tl(tmp, cpu_env, offsetof(CPURISCVState, mstatus));
> +        tcg_temp_free(tmp);
> +    }
>
> -    tcg_gen_ld_tl(tmp, cpu_env, offsetof(CPURISCVState, mstatus));
> -    tcg_gen_ori_tl(tmp, tmp, MSTATUS_FS | sd);
> -    tcg_gen_st_tl(tmp, cpu_env, offsetof(CPURISCVState, mstatus));
> +    if (ctx->virt_enabled && ctx->mstatus_hs_fs != MSTATUS_FS) {
> +        /* Remember the stage change for the rest of the TB. */
> +        ctx->mstatus_hs_fs = MSTATUS_FS;
>
> -    if (ctx->virt_enabled) {
> +        tmp = tcg_temp_new();
>          tcg_gen_ld_tl(tmp, cpu_env, offsetof(CPURISCVState, mstatus_hs));
>          tcg_gen_ori_tl(tmp, tmp, MSTATUS_FS | sd);
>          tcg_gen_st_tl(tmp, cpu_env, offsetof(CPURISCVState, mstatus_hs));
> +        tcg_temp_free(tmp);
>      }
> -    tcg_temp_free(tmp);
>  }
>  #else
>  static inline void mark_fs_dirty(DisasContext *ctx) { }
> @@ -533,6 +536,7 @@ static void riscv_tr_init_disas_context(DisasContextBase 
> *dcbase, CPUState *cs)
>      ctx->frm = -1;  /* unknown rounding mode */
>      ctx->ext_ifencei = cpu->cfg.ext_ifencei;
>      ctx->vlen = cpu->cfg.vlen;
> +    ctx->mstatus_hs_fs = FIELD_EX32(tb_flags, TB_FLAGS, MSTATUS_HS_FS);
>      ctx->hlsx = FIELD_EX32(tb_flags, TB_FLAGS, HLSX);
>      ctx->vill = FIELD_EX32(tb_flags, TB_FLAGS, VILL);
>      ctx->sew = FIELD_EX32(tb_flags, TB_FLAGS, SEW);
> --
> 2.25.1
>
>