Re: [RFC PATCH 07/11] target/riscv: Update CSR xtvt in CLIC mode

[Frank Chang <frank.chang@sifive.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 xtvt WARL XLEN-bit CSR holds the base address of the trap vector table,
> aligned on a 64-byte or greater power-of-two boundary.
>
> Signed-off-by: LIU Zhiwei <zhiwei_liu@c-sky.com>
> ---
>  target/riscv/cpu.h      |  2 ++
>  target/riscv/cpu_bits.h |  2 ++
>  target/riscv/csr.c      | 28 ++++++++++++++++++++++++++++
>  3 files changed, 32 insertions(+)
>
> diff --git a/target/riscv/cpu.h b/target/riscv/cpu.h
> index 9e389d7bbf..b5fd796f98 100644
> --- a/target/riscv/cpu.h
> +++ b/target/riscv/cpu.h
> @@ -173,11 +173,13 @@ struct CPURISCVState {
>      target_ulong medeleg;
>
>      target_ulong stvec;
> +    target_ulong stvt; /* clic-spec */
>      target_ulong sepc;
>      target_ulong scause;
>      target_ulong sintthresh; /* clic-spec */
>
>      target_ulong mtvec;
> +    target_ulong mtvt; /* clic-spec */
>      target_ulong mepc;
>      target_ulong mcause;
>      target_ulong mtval;  /* since: priv-1.10.0 */
> diff --git a/target/riscv/cpu_bits.h b/target/riscv/cpu_bits.h
> index 9447801d22..7922097776 100644
> --- a/target/riscv/cpu_bits.h
> +++ b/target/riscv/cpu_bits.h
> @@ -149,6 +149,7 @@
>  #define CSR_MIE             0x304
>  #define CSR_MTVEC           0x305
>  #define CSR_MCOUNTEREN      0x306
> +#define CSR_MTVT            0x307 /* clic-spec-draft */
>
>  /* 32-bit only */
>  #define CSR_MSTATUSH        0x310
> @@ -178,6 +179,7 @@
>  #define CSR_SIE             0x104
>  #define CSR_STVEC           0x105
>  #define CSR_SCOUNTEREN      0x106
> +#define CSR_STVT            0x107 /* clic-spec-draft */
>
>  /* Supervisor Trap Handling */
>  #define CSR_SSCRATCH        0x140
> diff --git a/target/riscv/csr.c b/target/riscv/csr.c
> index 39ff72041a..e12222b77f 100644
> --- a/target/riscv/csr.c
> +++ b/target/riscv/csr.c
> @@ -667,6 +667,18 @@ static int write_mcounteren(CPURISCVState *env, int
> csrno, target_ulong val)
>      return 0;
>  }
>
> +static int read_mtvt(CPURISCVState *env, int csrno, target_ulong *val)
> +{
> +    *val = env->mtvt;
> +    return 0;
> +}
> +
> +static int write_mtvt(CPURISCVState *env, int csrno, target_ulong val)
> +{
> +    env->mtvt = val & ~((1ULL << 6) - 1);
>

mtvt CSR has additional minimum alignment restriction in v0.8 CLIC spec[1]:
  2^ceiling(log2(N)) x 4 bytes, where N is the maximum number of interrupt
sources.


> +    return 0;
> +}
> +
>  /* This regiser is replaced with CSR_MCOUNTINHIBIT in 1.11.0 */
>  static int read_mscounteren(CPURISCVState *env, int csrno, target_ulong
> *val)
>  {
> @@ -876,6 +888,18 @@ static int write_scounteren(CPURISCVState *env, int
> csrno, target_ulong val)
>      return 0;
>  }
>
> +static int read_stvt(CPURISCVState *env, int csrno, target_ulong *val)


stvt CSR seems not to exist in v0.8 CLIC spec[1].

[1] https://github.com/riscv/riscv-fast-interrupt/blob/74f86c3858/clic.adoc

Regards,
Frank Chang


>

+{
> +    *val = env->stvt;
> +    return 0;
> +}
> +
> +static int write_stvt(CPURISCVState *env, int csrno, target_ulong val)
> +{
> +    env->stvt = val & ~((1ULL << 6) - 1);
> +    return 0;
> +}
> +
>  /* Supervisor Trap Handling */
>  static int read_sscratch(CPURISCVState *env, int csrno, target_ulong *val)
>  {
> @@ -1730,6 +1754,7 @@ riscv_csr_operations csr_ops[CSR_TABLE_SIZE] = {
>      [CSR_MHPMCOUNTER31H] = { "mhpmcounter31h", any32,  read_zero },
>
>      /* Machine Mode Core Level Interrupt Controller */
> +    [CSR_MTVT] = { "mtvt", clic,  read_mtvt,  write_mtvt      },
>      [CSR_MINTSTATUS] = { "mintstatus", clic,  read_mintstatus },
>      [CSR_MINTTHRESH] = { "mintthresh", clic,  read_mintthresh,
>                           write_mintthresh },
> @@ -1739,5 +1764,8 @@ riscv_csr_operations csr_ops[CSR_TABLE_SIZE] = {
>      [CSR_SINTTHRESH] = { "sintthresh", clic,  read_sintthresh,
>                           write_sintthresh },
>
> +    /* Supervisor Mode Core Level Interrupt Controller */
> +    [CSR_STVT] = { "stvt", clic,  read_stvt, write_stvt       },
> +
>  #endif /* !CONFIG_USER_ONLY */
>  };
> --
> 2.25.1
>
>
>

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