Re: [PATCH v5 04/13] riscv: sbi: add SBI FWFT extension calls

Andrew Jones
2025-04-24T12:54:41Z

On Thu, Apr 17, 2025 at 02:19:51PM +0200, Clément Léger wrote:
> Add FWFT extension calls. This will be ratified in SBI V3.0 hence, it is
> provided as a separate commit that can be left out if needed.
>
> Signed-off-by: Clément Léger <cleger@rivosinc.com>
> ---
> arch/riscv/kernel/sbi.c | 20 +++++++++++++++++++-
> 1 file changed, 19 insertions(+), 1 deletion(-)
>
> diff --git a/arch/riscv/kernel/sbi.c b/arch/riscv/kernel/sbi.c
> index 379981c2bb21..7b062189b184 100644
> --- a/arch/riscv/kernel/sbi.c
> +++ b/arch/riscv/kernel/sbi.c
> @@ -299,6 +299,8 @@ static int __sbi_rfence_v02(int fid, const struct cpumask *cpu_mask,
> return 0;
> }
>
> +static bool sbi_fwft_supported;

At some point we may want an SBI extension bitmap, but this is only the
second SBI extension supported boolean that I'm aware of, so I guess we're
still OK for now.

> +
> /**
> * sbi_fwft_set() - Set a feature on the local hart
> * @feature: The feature ID to be set
> @@ -309,7 +311,15 @@ static int __sbi_rfence_v02(int fid, const struct cpumask *cpu_mask,
> */
> int sbi_fwft_set(u32 feature, unsigned long value, unsigned long flags)
> {
> - return -EOPNOTSUPP;
> + struct sbiret ret;
> +
> + if (!sbi_fwft_supported)
> + return -EOPNOTSUPP;
> +
> + ret = sbi_ecall(SBI_EXT_FWFT, SBI_EXT_FWFT_SET,
> + feature, value, flags, 0, 0, 0);
> +
> + return sbi_err_map_linux_errno(ret.error);
> }
>
> struct fwft_set_req {
> @@ -348,6 +358,9 @@ int sbi_fwft_local_set_cpumask(const cpumask_t *mask, u32 feature,
> .error = ATOMIC_INIT(0),
> };
>
> + if (!sbi_fwft_supported)
> + return -EOPNOTSUPP;
> +
> if (feature & SBI_FWFT_GLOBAL_FEATURE_BIT)
> return -EINVAL;
>
> @@ -679,6 +692,11 @@ void __init sbi_init(void)
> pr_info("SBI DBCN extension detected\n");
> sbi_debug_console_available = true;
> }
> + if ((sbi_spec_version >= sbi_mk_version(3, 0)) &&
> + (sbi_probe_extension(SBI_EXT_FWFT) > 0)) {

Unnecessary (), but I see it's consistent with the expressions above.

> + pr_info("SBI FWFT extension detected\n");
> + sbi_fwft_supported = true;
> + }
> } else {
> __sbi_set_timer = __sbi_set_timer_v01;
> __sbi_send_ipi = __sbi_send_ipi_v01;
> --
> 2.49.0
>

Besides the () nit