Re: [Qemu-devel] [PATCH 2/2] target/riscv: Mark MSTATUS_FS dirty

[Michael Clark]

On Wed, Mar 28, 2018 at 10:36 AM, Michael Clark <address@hidden> wrote:

>
>
> On Tue, Mar 27, 2018 at 7:22 PM, Richard Henderson <
> address@hidden> wrote:
>
>> Writes to the FP register file mark the register file as dirty.
>>
>> Signed-off-by: Richard Henderson <address@hidden>
>> ---
>>  target/riscv/op_helper.c | 25 +++++++++++++++++--------
>>  target/riscv/translate.c | 40 +++++++++++++++++++++++++++++++++++++++-
>>  2 files changed, 56 insertions(+), 9 deletions(-)
>>
>> diff --git a/target/riscv/op_helper.c b/target/riscv/op_helper.c
>> index e34715df4e..74eeef0be8 100644
>> --- a/target/riscv/op_helper.c
>> +++ b/target/riscv/op_helper.c
>> @@ -72,11 +72,20 @@ void helper_raise_exception(CPURISCVState *env,
>> uint32_t exception)
>>      do_raise_exception_err(env, exception, 0);
>>  }
>>
>> -static void validate_mstatus_fs(CPURISCVState *env, uintptr_t ra)
>> +static void validate_mstatus_fs(CPURISCVState *env, uintptr_t ra, bool
>> write)
>>  {
>>  #ifndef CONFIG_USER_ONLY
>> -    if (!(env->mstatus & MSTATUS_FS)) {
>> +    switch (get_field(env->mstatus, MSTATUS_FS)) {
>> +    case 0: /* disabled */
>>          do_raise_exception_err(env, RISCV_EXCP_ILLEGAL_INST, ra);
>> +        g_assert_not_reached();
>> +    case 1: /* initial */
>> +    case 2: /* clean */
>> +        if (write) {
>> +            /* Mark fp status as dirty.  */
>> +            env->mstatus = MSTATUS_FS;
>> +        }
>> +        break;
>>      }
>>  #endif
>>  }
>> @@ -96,15 +105,15 @@ void csr_write_helper(CPURISCVState *env,
>> target_ulong val_to_write,
>>
>>      switch (csrno) {
>>      case CSR_FFLAGS:
>> -        validate_mstatus_fs(env, GETPC());
>> +        validate_mstatus_fs(env, GETPC(), true);
>>          cpu_riscv_set_fflags(env, val_to_write & (FSR_AEXC >>
>> FSR_AEXC_SHIFT));
>>          break;
>>      case CSR_FRM:
>> -        validate_mstatus_fs(env, GETPC());
>> +        validate_mstatus_fs(env, GETPC(), true);
>>          env->frm = val_to_write & (FSR_RD >> FSR_RD_SHIFT);
>>          break;
>>      case CSR_FCSR:
>> -        validate_mstatus_fs(env, GETPC());
>> +        validate_mstatus_fs(env, GETPC(), true);
>>          env->frm = (val_to_write & FSR_RD) >> FSR_RD_SHIFT;
>>          cpu_riscv_set_fflags(env, (val_to_write & FSR_AEXC) >>
>> FSR_AEXC_SHIFT);
>>          break;
>> @@ -379,13 +388,13 @@ target_ulong csr_read_helper(CPURISCVState *env,
>> target_ulong csrno)
>>
>>      switch (csrno) {
>>      case CSR_FFLAGS:
>> -        validate_mstatus_fs(env, GETPC());
>> +        validate_mstatus_fs(env, GETPC(), false);
>>          return cpu_riscv_get_fflags(env);
>>      case CSR_FRM:
>> -        validate_mstatus_fs(env, GETPC());
>> +        validate_mstatus_fs(env, GETPC(), false);
>>          return env->frm;
>>      case CSR_FCSR:
>> -        validate_mstatus_fs(env, GETPC());
>> +        validate_mstatus_fs(env, GETPC(), false);
>>          return (cpu_riscv_get_fflags(env) << FSR_AEXC_SHIFT)
>>                  | (env->frm << FSR_RD_SHIFT);
>>      /* rdtime/rdtimeh is trapped and emulated by bbl in system mode */
>> diff --git a/target/riscv/translate.c b/target/riscv/translate.c
>> index a30724aa90..08fc42a679 100644
>> --- a/target/riscv/translate.c
>> +++ b/target/riscv/translate.c
>> @@ -660,6 +660,31 @@ static void gen_store(DisasContext *ctx, uint32_t
>> opc, int rs1, int rs2,
>>      tcg_temp_free(dat);
>>  }
>>
>> +#ifndef CONFIG_USER_ONLY
>> +/* The states of mstatus_fs are:
>> + * 0 = disabled, 1 = initial, 2 = clean, 3 = dirty
>> + * We will have already diagnosed disabled state,
>> + * and need to turn initial/clean into dirty.
>> + */
>> +static void mark_fs_dirty(DisasContext *ctx)
>> +{
>> +    TCGv tmp;
>> +    if (ctx->mstatus_fs == MSTATUS_FS) {
>> +        return;
>> +    }
>> +    /* Remember the state change for the rest of the TB.  */
>> +    ctx->mstatus_fs = MSTATUS_FS;
>> +
>> +    tmp = tcg_temp_new();
>> +    tcg_gen_ld_tl(tmp, cpu_env, offsetof(CPURISCVState, mstatus));
>> +    tcg_gen_ori_tl(tmp, tmp, MSTATUS_FS);
>> +    tcg_gen_st_tl(tmp, cpu_env, offsetof(CPURISCVState, mstatus));
>> +    tcg_temp_free(tmp);
>> +}
>> +#else
>> +static inline void mark_fs_dirty(DisasContext *ctx) { }
>> +#endif
>> +
>>  static void gen_fp_load(DisasContext *ctx, uint32_t opc, int rd,
>>          int rs1, target_long imm)
>>  {
>> @@ -688,6 +713,8 @@ static void gen_fp_load(DisasContext *ctx, uint32_t
>> opc, int rd,
>>          break;
>>      }
>>      tcg_temp_free(t0);
>> +
>> +    mark_fs_dirty(ctx);
>>  }
>>
>
> Don't we want the mark_fs_dirty(ctx) to be at the end of gen_fp_store
> instead of gen_fp_load?
>

Sorry I was thinking of storing to the fp register file vs storing to
memory. The code is of course correct.


>  static void gen_fp_store(DisasContext *ctx, uint32_t opc, int rs1,
>> @@ -985,6 +1012,7 @@ static void gen_fp_arith(DisasContext *ctx, uint32_t
>> opc, int rd,
>>                           int rs1, int rs2, int rm)
>>  {
>>      TCGv t0 = NULL;
>> +    bool fp_output = true;
>>
>>      if (ctx->mstatus_fs == 0) {
>>          goto do_illegal;
>> @@ -1047,6 +1075,7 @@ static void gen_fp_arith(DisasContext *ctx,
>> uint32_t opc, int rd,
>>          }
>>          gen_set_gpr(rd, t0);
>>          tcg_temp_free(t0);
>> +        fp_output = false;
>>          break;
>>
>>      case OPC_RISC_FCVT_W_S:
>> @@ -1076,6 +1105,7 @@ static void gen_fp_arith(DisasContext *ctx,
>> uint32_t opc, int rd,
>>          }
>>          gen_set_gpr(rd, t0);
>>          tcg_temp_free(t0);
>> +        fp_output = false;
>>          break;
>>
>>      case OPC_RISC_FCVT_S_W:
>> @@ -1126,6 +1156,7 @@ static void gen_fp_arith(DisasContext *ctx,
>> uint32_t opc, int rd,
>>          }
>>          gen_set_gpr(rd, t0);
>>          tcg_temp_free(t0);
>> +        fp_output = false;
>>          break;
>>
>>      case OPC_RISC_FMV_S_X:
>> @@ -1218,6 +1249,7 @@ static void gen_fp_arith(DisasContext *ctx,
>> uint32_t opc, int rd,
>>          }
>>          gen_set_gpr(rd, t0);
>>          tcg_temp_free(t0);
>> +        fp_output = false;
>>          break;
>>
>>      case OPC_RISC_FCVT_W_D:
>> @@ -1247,6 +1279,7 @@ static void gen_fp_arith(DisasContext *ctx,
>> uint32_t opc, int rd,
>>          }
>>          gen_set_gpr(rd, t0);
>>          tcg_temp_free(t0);
>> +        fp_output = false;
>>          break;
>>
>>      case OPC_RISC_FCVT_D_W:
>> @@ -1294,6 +1327,7 @@ static void gen_fp_arith(DisasContext *ctx,
>> uint32_t opc, int rd,
>>          default:
>>              goto do_illegal;
>>          }
>> +        fp_output = false;
>>          break;
>>
>>      case OPC_RISC_FMV_D_X:
>> @@ -1310,7 +1344,11 @@ static void gen_fp_arith(DisasContext *ctx,
>> uint32_t opc, int rd,
>>              tcg_temp_free(t0);
>>          }
>>          gen_exception_illegal(ctx);
>> -        break;
>> +        return;
>> +    }
>> +
>> +    if (fp_output) {
>> +        mark_fs_dirty(ctx);
>>      }
>>  }
>>
>> --
>> 2.14.3
>>
>>
>