Re: [ RFC 2/6] target/riscv: Implement mcountinhibit CSR

[Alistair Francis]

On Fri, Mar 19, 2021 at 3:46 PM Atish Patra <atish.patra@wdc.com> wrote:
>
> As per the privilege specification v1.11, mcountinhibit allows to start/stop
> a pmu counter selectively.
>
> Signed-off-by: Atish Patra <atish.patra@wdc.com>
> ---
>  target/riscv/cpu.h      |  2 ++
>  target/riscv/cpu_bits.h |  4 ++++
>  target/riscv/csr.c      | 23 +++++++++++++++++++++++
>  target/riscv/machine.c  |  1 +
>  4 files changed, 30 insertions(+)
>
> diff --git a/target/riscv/cpu.h b/target/riscv/cpu.h
> index 7bee351f3c99..ef2a7fdc3980 100644
> --- a/target/riscv/cpu.h
> +++ b/target/riscv/cpu.h
> @@ -214,6 +214,8 @@ struct CPURISCVState {
>      target_ulong scounteren;
>      target_ulong mcounteren;
>
> +    target_ulong mcountinhibit;
> +
>      target_ulong sscratch;
>      target_ulong mscratch;
>
> diff --git a/target/riscv/cpu_bits.h b/target/riscv/cpu_bits.h
> index b42dd4f8d8b1..7514d611cd0b 100644
> --- a/target/riscv/cpu_bits.h
> +++ b/target/riscv/cpu_bits.h
> @@ -283,6 +283,10 @@
>  #define CSR_MHPMCOUNTER29   0xb1d
>  #define CSR_MHPMCOUNTER30   0xb1e
>  #define CSR_MHPMCOUNTER31   0xb1f
> +
> +/* Machine counter-inhibit register */
> +#define CSR_MCOUNTINHIBIT   0x320
> +
>  #define CSR_MHPMEVENT3      0x323
>  #define CSR_MHPMEVENT4      0x324
>  #define CSR_MHPMEVENT5      0x325
> diff --git a/target/riscv/csr.c b/target/riscv/csr.c
> index 7166f8d710a8..b9d795389532 100644
> --- a/target/riscv/csr.c
> +++ b/target/riscv/csr.c
> @@ -631,6 +631,26 @@ static int write_mtvec(CPURISCVState *env, int csrno, 
> target_ulong val)
>      return 0;
>  }
>
> +static int read_mcountinhibit(CPURISCVState *env, int csrno, target_ulong 
> *val)
> +{
> +    if (env->priv_ver < PRIV_VERSION_1_11_0) {
> +        return -RISCV_EXCP_ILLEGAL_INST;
> +    }
> +
> +    *val = env->mcountinhibit;
> +    return 0;
> +}
> +
> +static int write_mcountinhibit(CPURISCVState *env, int csrno, target_ulong 
> val)
> +{
> +    if (env->priv_ver < PRIV_VERSION_1_11_0) {
> +        return -RISCV_EXCP_ILLEGAL_INST;
> +    }
> +
> +    env->mcountinhibit = val;
> +    return 0;
> +}

This will probably need a rebase as a large change to CSR access
functions is in the works.

> +
>  static int read_mcounteren(CPURISCVState *env, int csrno, target_ulong *val)
>  {
>      *val = env->mcounteren;
> @@ -1533,6 +1553,9 @@ riscv_csr_operations csr_ops[CSR_TABLE_SIZE] = {
>      [CSR_MHPMCOUNTER30]  = { "mhpmcounter30",  any,    read_zero },
>      [CSR_MHPMCOUNTER31]  = { "mhpmcounter31",  any,    read_zero },
>
> +    [CSR_MCOUNTINHIBIT]  = { "mcountinhibi",   any,    read_mcountinhibit,
> +                                                       write_mcountinhibit },
> +
>      [CSR_MHPMEVENT3]     = { "mhpmevent3",     any,    read_zero },
>      [CSR_MHPMEVENT4]     = { "mhpmevent4",     any,    read_zero },
>      [CSR_MHPMEVENT5]     = { "mhpmevent5",     any,    read_zero },
> diff --git a/target/riscv/machine.c b/target/riscv/machine.c
> index 27fcc770aa4b..cb7ec8a4c656 100644
> --- a/target/riscv/machine.c
> +++ b/target/riscv/machine.c
> @@ -177,6 +177,7 @@ const VMStateDescription vmstate_riscv_cpu = {
>          VMSTATE_UINTTL(env.mtval, RISCVCPU),
>          VMSTATE_UINTTL(env.scounteren, RISCVCPU),
>          VMSTATE_UINTTL(env.mcounteren, RISCVCPU),
> +        VMSTATE_UINTTL(env.mcountinhibit, RISCVCPU),
>          VMSTATE_UINTTL(env.sscratch, RISCVCPU),
>          VMSTATE_UINTTL(env.mscratch, RISCVCPU),
>          VMSTATE_UINT64(env.mfromhost, RISCVCPU),

A bump will be required here.

Otherwise:

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

Alistair

> --
> 2.25.1
>
>