Re: [PATCH v4 14/22] target/riscv: Implement AIA xiselect and xireg CSRs

[Alistair Francis]

On Tue, Oct 26, 2021 at 6:08 PM Anup Patel <anup.patel@wdc.com> wrote:
>
> The AIA specification defines [m|s|vs]iselect and [m|s|vs]ireg CSRs
> which allow indirect access to interrupt priority arrays and per-HART
> IMSIC registers. This patch implements AIA xiselect and xireg CSRs.
>
> Signed-off-by: Anup Patel <anup.patel@wdc.com>
> ---
>  target/riscv/cpu.h     |   7 ++
>  target/riscv/csr.c     | 174 +++++++++++++++++++++++++++++++++++++++++
>  target/riscv/machine.c |   3 +
>  3 files changed, 184 insertions(+)
>
> diff --git a/target/riscv/cpu.h b/target/riscv/cpu.h
> index 21d9c536ef..bf688eb1ea 100644
> --- a/target/riscv/cpu.h
> +++ b/target/riscv/cpu.h
> @@ -183,6 +183,10 @@ struct CPURISCVState {
>      uint8_t miprio[64];
>      uint8_t siprio[64];
>
> +    /* AIA CSRs */
> +    target_ulong miselect;
> +    target_ulong siselect;
> +
>      /* Hypervisor CSRs */
>      target_ulong hstatus;
>      target_ulong hedeleg;
> @@ -212,6 +216,9 @@ struct CPURISCVState {
>      target_ulong vstval;
>      target_ulong vsatp;
>
> +    /* AIA VS-mode CSRs */
> +    target_ulong vsiselect;
> +
>      target_ulong mtval2;
>      target_ulong mtinst;
>
> diff --git a/target/riscv/csr.c b/target/riscv/csr.c
> index 69e857d1e5..e72220fd0f 100644
> --- a/target/riscv/csr.c
> +++ b/target/riscv/csr.c
> @@ -854,6 +854,168 @@ static int read_mtopi(CPURISCVState *env, int csrno, 
> target_ulong *val)
>      return RISCV_EXCP_NONE;
>  }
>
> +static int aia_xlate_vs_csrno(CPURISCVState *env, int csrno)
> +{
> +    if (!riscv_cpu_virt_enabled(env)) {
> +        return csrno;
> +    }
> +
> +    switch (csrno) {
> +    case CSR_SISELECT:
> +        return CSR_VSISELECT;
> +    case CSR_SIREG:
> +        return CSR_VSIREG;
> +    default:
> +        return csrno;
> +    };
> +}
> +
> +static int rmw_xiselect(CPURISCVState *env, int csrno, target_ulong *val,
> +                        target_ulong new_val, target_ulong wr_mask)
> +{
> +    target_ulong *iselect;
> +
> +    /* Translate CSR number for VS-mode */
> +    csrno = aia_xlate_vs_csrno(env, csrno);
> +
> +    /* Find the iselect CSR based on CSR number */
> +    switch (csrno) {
> +    case CSR_MISELECT:
> +        iselect = &env->miselect;
> +        break;
> +    case CSR_SISELECT:
> +        iselect = &env->siselect;
> +        break;
> +    case CSR_VSISELECT:
> +        iselect = &env->vsiselect;
> +        break;
> +    default:
> +         return RISCV_EXCP_ILLEGAL_INST;
> +    };
> +
> +    if (val) {
> +        *val = *iselect;
> +    }
> +
> +    wr_mask &= ISELECT_MASK;
> +    if (wr_mask) {
> +        *iselect = (*iselect & ~wr_mask) | (new_val & wr_mask);
> +    }
> +
> +    return RISCV_EXCP_NONE;
> +}
> +
> +static int rmw_iprio(target_ulong iselect, uint8_t *iprio,
> +                     target_ulong *val, target_ulong new_val,
> +                     target_ulong wr_mask, int ext_irq_no)
> +{
> +    int i, firq, nirqs;
> +    target_ulong old_val;
> +
> +    if (iselect < ISELECT_IPRIO0 || ISELECT_IPRIO15 < iselect) {
> +        return -EINVAL;
> +    }
> +#if TARGET_LONG_BITS == 64
> +    if (iselect & 0x1) {
> +        return -EINVAL;
> +    }
> +#endif
> +
> +    nirqs = 4 * (TARGET_LONG_BITS / 32);
> +    firq = ((iselect - ISELECT_IPRIO0) / (TARGET_LONG_BITS / 32)) * (nirqs);

Don't use TARGET_LONG_BITS, this should be checked at runtime instead

Alistair