Re: [PATCH 3/4] target/riscv: Set [m|s]tval for both illegal and virtual instruction traps

[Alistair Francis]

On Fri, Apr 29, 2022 at 5:36 AM Anup Patel <apatel@ventanamicro.com> wrote:>
> Currently, the [m|s]tval CSRs are set with trapping instruction encoding
> only for illegal instruction traps taken at the time of instruction
> decoding.
>
> In RISC-V world, a valid instructions might also trap as illegal or
> virtual instruction based to trapping bits in various CSRs (such as
> mstatus.TVM or hstatus.VTVM).
>
> We improve setting of [m|s]tval CSRs for all types of illegal and
> virtual instruction traps.
>
> Signed-off-by: Anup Patel <apatel@ventanamicro.com>

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

Alistair

> ---
>  target/riscv/cpu.c        |  2 ++
>  target/riscv/cpu.h        |  8 +++++++-
>  target/riscv/cpu_helper.c |  1 +
>  target/riscv/translate.c  | 17 +++++++++++++----
>  4 files changed, 23 insertions(+), 5 deletions(-)
>
> diff --git a/target/riscv/cpu.c b/target/riscv/cpu.c
> index dff4606585..f0a702fee6 100644
> --- a/target/riscv/cpu.c
> +++ b/target/riscv/cpu.c
> @@ -406,6 +406,7 @@ void restore_state_to_opc(CPURISCVState *env, 
> TranslationBlock *tb,
>      } else {
>          env->pc = data[0];
>      }
> +    env->bins = data[1];
>  }
>
>  static void riscv_cpu_reset(DeviceState *dev)
> @@ -445,6 +446,7 @@ static void riscv_cpu_reset(DeviceState *dev)
>      env->mcause = 0;
>      env->miclaim = MIP_SGEIP;
>      env->pc = env->resetvec;
> +    env->bins = 0;
>      env->two_stage_lookup = false;
>
>      /* Initialized default priorities of local interrupts. */
> diff --git a/target/riscv/cpu.h b/target/riscv/cpu.h
> index fe6c9a2c92..a55c918274 100644
> --- a/target/riscv/cpu.h
> +++ b/target/riscv/cpu.h
> @@ -30,6 +30,12 @@
>
>  #define TCG_GUEST_DEFAULT_MO 0
>
> +/*
> + * RISC-V-specific extra insn start words:
> + * 1: Original instruction opcode
> + */
> +#define TARGET_INSN_START_EXTRA_WORDS 1
> +
>  #define TYPE_RISCV_CPU "riscv-cpu"
>
>  #define RISCV_CPU_TYPE_SUFFIX "-" TYPE_RISCV_CPU
> @@ -140,7 +146,7 @@ struct CPUArchState {
>      target_ulong frm;
>
>      target_ulong badaddr;
> -    uint32_t bins;
> +    target_ulong bins;
>
>      target_ulong guest_phys_fault_addr;
>
> diff --git a/target/riscv/cpu_helper.c b/target/riscv/cpu_helper.c
> index d83579accf..bba4fce777 100644
> --- a/target/riscv/cpu_helper.c
> +++ b/target/riscv/cpu_helper.c
> @@ -1371,6 +1371,7 @@ void riscv_cpu_do_interrupt(CPUState *cs)
>              tval = env->badaddr;
>              break;
>          case RISCV_EXCP_ILLEGAL_INST:
> +        case RISCV_EXCP_VIRT_INSTRUCTION_FAULT:
>              tval = env->bins;
>              break;
>          default:
> diff --git a/target/riscv/translate.c b/target/riscv/translate.c
> index 0cd1d9ee94..55a4713af2 100644
> --- a/target/riscv/translate.c
> +++ b/target/riscv/translate.c
> @@ -107,6 +107,8 @@ typedef struct DisasContext {
>      /* PointerMasking extension */
>      bool pm_mask_enabled;
>      bool pm_base_enabled;
> +    /* TCG of the current insn_start */
> +    TCGOp *insn_start;
>  } DisasContext;
>
>  static inline bool has_ext(DisasContext *ctx, uint32_t ext)
> @@ -236,9 +238,6 @@ static void generate_exception_mtval(DisasContext *ctx, 
> int excp)
>
>  static void gen_exception_illegal(DisasContext *ctx)
>  {
> -    tcg_gen_st_i32(tcg_constant_i32(ctx->opcode), cpu_env,
> -                   offsetof(CPURISCVState, bins));
> -
>      generate_exception(ctx, RISCV_EXCP_ILLEGAL_INST);
>  }
>
> @@ -1017,6 +1016,13 @@ static uint32_t opcode_at(DisasContextBase *dcbase, 
> target_ulong pc)
>  /* Include decoders for factored-out extensions */
>  #include "decode-XVentanaCondOps.c.inc"
>
> +static inline void decode_save_opc(DisasContext *ctx, target_ulong opc)
> +{
> +    assert(ctx->insn_start != NULL);
> +    tcg_set_insn_start_param(ctx->insn_start, 1, opc);
> +    ctx->insn_start = NULL;
> +}
> +
>  static void decode_opc(CPURISCVState *env, DisasContext *ctx, uint16_t 
> opcode)
>  {
>      /*
> @@ -1033,6 +1039,7 @@ static void decode_opc(CPURISCVState *env, DisasContext 
> *ctx, uint16_t opcode)
>
>      /* Check for compressed insn */
>      if (extract16(opcode, 0, 2) != 3) {
> +        decode_save_opc(ctx, opcode);
>          if (!has_ext(ctx, RVC)) {
>              gen_exception_illegal(ctx);
>          } else {
> @@ -1047,6 +1054,7 @@ static void decode_opc(CPURISCVState *env, DisasContext 
> *ctx, uint16_t opcode)
>          opcode32 = deposit32(opcode32, 16, 16,
>                               translator_lduw(env, &ctx->base,
>                                               ctx->base.pc_next + 2));
> +        decode_save_opc(ctx, opcode32);
>          ctx->opcode = opcode32;
>          ctx->pc_succ_insn = ctx->base.pc_next + 4;
>
> @@ -1113,7 +1121,8 @@ static void riscv_tr_insn_start(DisasContextBase 
> *dcbase, CPUState *cpu)
>  {
>      DisasContext *ctx = container_of(dcbase, DisasContext, base);
>
> -    tcg_gen_insn_start(ctx->base.pc_next);
> +    tcg_gen_insn_start(ctx->base.pc_next, 0);
> +    ctx->insn_start = tcg_last_op();
>  }
>
>  static void riscv_tr_translate_insn(DisasContextBase *dcbase, CPUState *cpu)
> --
> 2.34.1
>
>