Re: [RFC PATCH 08/11] target/riscv: Update CSR xnxti in CLIC mode

[Frank Chang <0xc0de0125@gmail.com>]

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LIU Zhiwei <zhiwei_liu@c-sky.com> 於 2021年4月9日 週五 下午3:52寫道：

> The CSR can be used by software to service the next horizontal interrupt
> when it has greater level than the saved interrupt context
> (held in xcause`.pil`) and greater level than the interrupt threshold of
> the corresponding privilege mode,
>
> Signed-off-by: LIU Zhiwei <zhiwei_liu@c-sky.com>
> ---
>  target/riscv/cpu_bits.h |  16 ++++++
>  target/riscv/csr.c      | 114 ++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 130 insertions(+)
>
> diff --git a/target/riscv/cpu_bits.h b/target/riscv/cpu_bits.h
> index 7922097776..494e41edc9 100644
> --- a/target/riscv/cpu_bits.h
> +++ b/target/riscv/cpu_bits.h
> @@ -166,6 +166,7 @@
>  #define CSR_MCAUSE          0x342
>  #define CSR_MTVAL           0x343
>  #define CSR_MIP             0x344
> +#define CSR_MNXTI           0x345 /* clic-spec-draft */
>  #define CSR_MINTSTATUS      0x346 /* clic-spec-draft */
>  #define CSR_MINTTHRESH      0x347 /* clic-spec-draft */
>
> @@ -187,6 +188,7 @@
>  #define CSR_SCAUSE          0x142
>  #define CSR_STVAL           0x143
>  #define CSR_SIP             0x144
> +#define CSR_SNXTI           0x145 /* clic-spec-draft */
>  #define CSR_SINTSTATUS      0x146 /* clic-spec-draft */
>  #define CSR_SINTTHRESH      0x147 /* clic-spec-draft */
>
> @@ -596,10 +598,24 @@
>  #define MINTSTATUS_SIL                     0x0000ff00 /* sil[7:0] */
>  #define MINTSTATUS_UIL                     0x000000ff /* uil[7:0] */
>
> +/* mcause */
> +#define MCAUSE_MINHV                       0x40000000 /* minhv */
> +#define MCAUSE_MPP                         0x30000000 /* mpp[1:0] */
> +#define MCAUSE_MPIE                        0x08000000 /* mpie */
> +#define MCAUSE_MPIL                        0x00ff0000 /* mpil[7:0] */
> +#define MCAUSE_EXCCODE                     0x00000fff /* exccode[11:0] */
> +
>  /* sintstatus */
>  #define SINTSTATUS_SIL                     0x0000ff00 /* sil[7:0] */
>  #define SINTSTATUS_UIL                     0x000000ff /* uil[7:0] */
>
> +/* scause */
> +#define SCAUSE_SINHV                       0x40000000 /* sinhv */
> +#define SCAUSE_SPP                         0x10000000 /* spp */
> +#define SCAUSE_SPIE                        0x08000000 /* spie */
> +#define SCAUSE_SPIL                        0x00ff0000 /* spil[7:0] */
> +#define SCAUSE_EXCCODE                     0x00000fff /* exccode[11:0] */
> +
>  /* MIE masks */
>  #define MIE_SEIE                           (1 << IRQ_S_EXT)
>  #define MIE_UEIE                           (1 << IRQ_U_EXT)
> diff --git a/target/riscv/csr.c b/target/riscv/csr.c
> index e12222b77f..72cba080bf 100644
> --- a/target/riscv/csr.c
> +++ b/target/riscv/csr.c
> @@ -774,6 +774,80 @@ static int rmw_mip(CPURISCVState *env, int csrno,
> target_ulong *ret_value,
>      return 0;
>  }
>
> +static bool get_xnxti_status(CPURISCVState *env)
> +{
> +    CPUState *cs = env_cpu(env);
> +    int clic_irq, clic_priv, clic_il, pil;
> +
> +    if (!env->exccode) { /* No interrupt */
> +        return false;
> +    }
> +    /* The system is not in a CLIC mode */
> +    if (!riscv_clic_is_clic_mode(env)) {
> +        return false;
> +    } else {
> +        riscv_clic_decode_exccode(env->exccode, &clic_priv, &clic_il,
> +                                  &clic_irq);
> +
> +        if (env->priv == PRV_M) {
> +            pil = MAX(get_field(env->mcause, MCAUSE_MPIL),
> env->mintthresh);
> +        } else if (env->priv == PRV_S) {
> +            pil = MAX(get_field(env->scause, SCAUSE_SPIL),
> env->sintthresh);
> +        } else {
> +            qemu_log_mask(LOG_GUEST_ERROR,
> +                          "CSR: rmw xnxti with unsupported mode\n");
> +            exit(1);
> +        }
> +
> +        if ((clic_priv != env->priv) || /* No horizontal interrupt */
> +            (clic_il <= pil) || /* No higher level interrupt */
> +            (riscv_clic_shv_interrupt(env->clic, clic_priv, cs->cpu_index,
> +                                      clic_irq))) { /* CLIC vector mode */
> +            return false;
> +        } else {
> +            return true;
> +        }
> +    }
> +}
> +
> +static int rmw_mnxti(CPURISCVState *env, int csrno, target_ulong
> *ret_value,
> +                     target_ulong new_value, target_ulong write_mask)
> +{
> +    int clic_priv, clic_il, clic_irq;
> +    bool ready;
> +    CPUState *cs = env_cpu(env);
> +    if (write_mask) {
> +        env->mstatus |= new_value & (write_mask & 0b11111);
> +    }
> +
> +    qemu_mutex_lock_iothread();
>

Hi Zhiwei,

May I ask what's the purpose to request the BQL here with
*qemu_mutex_lock_iothread()*?
Is there any critical data we need to protect in *rmw_mnxti()*?
As far I see, *rmw_mnxti()* won't call *cpu_interrupt()* which need BQL to
be held before calling.
Am I missing anything?

Regard,
Frank Chang


> +    ready = get_xnxti_status(env);
> +    if (ready) {
> +        riscv_clic_decode_exccode(env->exccode, &clic_priv, &clic_il,
> +                                  &clic_irq);
> +        if (write_mask) {
> +            bool edge = riscv_clic_edge_triggered(env->clic, clic_priv,
> +                                                  cs->cpu_index,
> clic_irq);
> +            if (edge) {
> +                riscv_clic_clean_pending(env->clic, clic_priv,
> +                                         cs->cpu_index, clic_irq);
> +            }
> +            env->mintstatus = set_field(env->mintstatus,
> +                                        MINTSTATUS_MIL, clic_il);
> +            env->mcause = set_field(env->mcause, MCAUSE_EXCCODE,
> clic_irq);
> +        }
> +        if (ret_value) {
> +            *ret_value = (env->mtvt & ~0x3f) + sizeof(target_ulong) *
> clic_irq;
> +        }
> +    } else {
> +        if (ret_value) {
> +            *ret_value = 0;
> +        }
> +    }
> +    qemu_mutex_unlock_iothread();
> +    return 0;
> +}
> +
>  static int read_mintstatus(CPURISCVState *env, int csrno, target_ulong
> *val)
>  {
>      *val = env->mintstatus;
> @@ -982,6 +1056,44 @@ static int rmw_sip(CPURISCVState *env, int csrno,
> target_ulong *ret_value,
>      return ret;
>  }
>
> +static int rmw_snxti(CPURISCVState *env, int csrno, target_ulong
> *ret_value,
> +                     target_ulong new_value, target_ulong write_mask)
> +{
> +    int clic_priv, clic_il, clic_irq;
> +    bool ready;
> +    CPUState *cs = env_cpu(env);
> +    if (write_mask) {
> +        env->mstatus |= new_value & (write_mask & 0b11111);
> +    }
> +
> +    qemu_mutex_lock_iothread();
> +    ready = get_xnxti_status(env);
> +    if (ready) {
> +        riscv_clic_decode_exccode(env->exccode, &clic_priv, &clic_il,
> +                                  &clic_irq);
> +        if (write_mask) {
> +            bool edge = riscv_clic_edge_triggered(env->clic, clic_priv,
> +                                                  cs->cpu_index,
> clic_irq);
> +            if (edge) {
> +                riscv_clic_clean_pending(env->clic, clic_priv,
> +                                         cs->cpu_index, clic_irq);
> +            }
> +            env->mintstatus = set_field(env->mintstatus,
> +                                        MINTSTATUS_SIL, clic_il);
> +            env->scause = set_field(env->scause, SCAUSE_EXCCODE,
> clic_irq);
> +        }
> +        if (ret_value) {
> +            *ret_value = (env->stvt & ~0x3f) + sizeof(target_ulong) *
> clic_irq;
> +        }
> +    } else {
> +        if (ret_value) {
> +            *ret_value = 0;
> +        }
> +    }
> +    qemu_mutex_unlock_iothread();
> +    return 0;
> +}
> +
>  static int read_sintstatus(CPURISCVState *env, int csrno, target_ulong
> *val)
>  {
>      target_ulong mask = SINTSTATUS_SIL | SINTSTATUS_UIL;
> @@ -1755,6 +1867,7 @@ riscv_csr_operations csr_ops[CSR_TABLE_SIZE] = {
>
>      /* Machine Mode Core Level Interrupt Controller */
>      [CSR_MTVT] = { "mtvt", clic,  read_mtvt,  write_mtvt      },
> +    [CSR_MNXTI] = { "mnxti", clic,  NULL,  NULL,  rmw_mnxti   },
>      [CSR_MINTSTATUS] = { "mintstatus", clic,  read_mintstatus },
>      [CSR_MINTTHRESH] = { "mintthresh", clic,  read_mintthresh,
>                           write_mintthresh },
> @@ -1766,6 +1879,7 @@ riscv_csr_operations csr_ops[CSR_TABLE_SIZE] = {
>
>      /* Supervisor Mode Core Level Interrupt Controller */
>      [CSR_STVT] = { "stvt", clic,  read_stvt, write_stvt       },
> +    [CSR_SNXTI] = { "snxti", clic,  NULL,  NULL,  rmw_snxti   },
>
>  #endif /* !CONFIG_USER_ONLY */
>  };
> --
> 2.25.1
>
>
>

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