Re: [PATCH v2 13/13] target/riscv: Enable PMU related extensions to preferred rule

[Andrew Jones]

On Tue, Jul 23, 2024 at 04:30:10PM GMT, Atish Patra wrote:
> Counter delegation/configuration extension requires the following
> extensions to be enabled.
> 
> 1. Smcdeleg - To enable counter delegation from M to S
> 2. S[m|s]csrind - To enable indirect access CSRs
> 3. Smstateen - Indirect CSR extensions depend on it.
> 4. Sscofpmf - To enable counter overflow feature
> 5. S[m|s]aia - To enable counter overflow feature in virtualization
> 6. Smcntrpmf - To enable privilege mode filtering for cycle/instret
> 
> While first 3 are mandatory to enable the counter delegation,
> next 3 set of extension are preferred to enable all the PMU related
> features.

Just my 2 cents, but I think for the first three we can apply the concept
of extension bundles, which we need for other extensions as well. In those
cases we just auto enable all the dependencies. For the three preferred
extensions I think we can just leave them off for 'base', but we should
enable them by default for 'max' along with Ssccfg.

Thanks,
drew

> That's why, enable all of these if Ssccfg extension is
> enabled from the commandline.
> 
> Signed-off-by: Atish Patra <atishp@rivosinc.com>
> ---
>  target/riscv/cpu.c | 14 +++++++++++++-
>  1 file changed, 13 insertions(+), 1 deletion(-)
> 
> diff --git a/target/riscv/cpu.c b/target/riscv/cpu.c
> index 22ba43c7ff2a..abebfcc46dea 100644
> --- a/target/riscv/cpu.c
> +++ b/target/riscv/cpu.c
> @@ -2665,8 +2665,20 @@ RISCVCPUImpliedExtsRule 
> *riscv_multi_ext_implied_rules[] = {
>      NULL
>  };
>  
> +static RISCVCPUPreferredExtsRule SSCCFG_PREFERRED = {
> +    .ext = CPU_CFG_OFFSET(ext_ssccfg),
> +    .preferred_multi_exts = {
> +        CPU_CFG_OFFSET(ext_smcsrind), CPU_CFG_OFFSET(ext_sscsrind),
> +        CPU_CFG_OFFSET(ext_ssaia), CPU_CFG_OFFSET(ext_smaia),
> +        CPU_CFG_OFFSET(ext_smstateen), CPU_CFG_OFFSET(ext_sscofpmf),
> +        CPU_CFG_OFFSET(ext_smcntrpmf), CPU_CFG_OFFSET(ext_smcdeleg),
> +
> +        RISCV_PREFRRED_EXTS_RULE_END
> +    },
> +};
> +
>  RISCVCPUPreferredExtsRule *riscv_multi_ext_preferred_rules[] = {
> -    NULL
> +    &SSCCFG_PREFERRED, NULL
>  };
>  
>  static Property riscv_cpu_properties[] = {
> 
> -- 
> 2.34.1
> 
>