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Message-ID: <1c385a47-0a01-4be4-a34b-51a2f168e62d@linux.dev>
Date: Thu, 8 May 2025 17:18:51 -0700
From: Atish Patra <atish.patra@...ux.dev>
To: Clément Léger <cleger@...osinc.com>,
Paul Walmsley <paul.walmsley@...ive.com>, Palmer Dabbelt
<palmer@...belt.com>, Anup Patel <anup@...infault.org>,
Atish Patra <atishp@...shpatra.org>, Shuah Khan <shuah@...nel.org>,
Jonathan Corbet <corbet@....net>, linux-riscv@...ts.infradead.org,
linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
kvm@...r.kernel.org, kvm-riscv@...ts.infradead.org,
linux-kselftest@...r.kernel.org
Cc: Samuel Holland <samuel.holland@...ive.com>,
Andrew Jones <ajones@...tanamicro.com>, Deepak Gupta <debug@...osinc.com>
Subject: Re: [PATCH v6 04/14] riscv: sbi: add FWFT extension interface
On 4/24/25 10:31 AM, Clément Léger wrote:
> This SBI extensions enables supervisor mode to control feature that are
> under M-mode control (For instance, Svadu menvcfg ADUE bit, Ssdbltrp
> DTE, etc). Add an interface to set local features for a specific cpu
> mask as well as for the online cpu mask.
>
> Signed-off-by: Clément Léger <cleger@...osinc.com>
> Reviewed-by: Andrew Jones <ajones@...tanamicro.com>
> ---
> arch/riscv/include/asm/sbi.h | 17 +++++++++++
> arch/riscv/kernel/sbi.c | 57 ++++++++++++++++++++++++++++++++++++
> 2 files changed, 74 insertions(+)
>
> diff --git a/arch/riscv/include/asm/sbi.h b/arch/riscv/include/asm/sbi.h
> index 7ec249fea880..3bbef56bcefc 100644
> --- a/arch/riscv/include/asm/sbi.h
> +++ b/arch/riscv/include/asm/sbi.h
> @@ -503,6 +503,23 @@ int sbi_remote_hfence_vvma_asid(const struct cpumask *cpu_mask,
> unsigned long asid);
> long sbi_probe_extension(int ext);
>
> +int sbi_fwft_set(u32 feature, unsigned long value, unsigned long flags);
> +int sbi_fwft_set_cpumask(const cpumask_t *mask, u32 feature,
> + unsigned long value, unsigned long flags);
> +/**
> + * sbi_fwft_set_online_cpus() - Set a feature on all online cpus
> + * @feature: The feature to be set
> + * @value: The feature value to be set
> + * @flags: FWFT feature set flags
> + *
> + * Return: 0 on success, appropriate linux error code otherwise.
> + */
> +static inline int sbi_fwft_set_online_cpus(u32 feature, unsigned long value,
> + unsigned long flags)
> +{
> + return sbi_fwft_set_cpumask(cpu_online_mask, feature, value, flags);
> +}
> +
> /* Check if current SBI specification version is 0.1 or not */
> static inline int sbi_spec_is_0_1(void)
> {
> diff --git a/arch/riscv/kernel/sbi.c b/arch/riscv/kernel/sbi.c
> index 1d44c35305a9..d57e4dae7dac 100644
> --- a/arch/riscv/kernel/sbi.c
> +++ b/arch/riscv/kernel/sbi.c
> @@ -299,6 +299,63 @@ static int __sbi_rfence_v02(int fid, const struct cpumask *cpu_mask,
> return 0;
> }
>
> +/**
> + * sbi_fwft_set() - Set a feature on the local hart
> + * @feature: The feature ID to be set
> + * @value: The feature value to be set
> + * @flags: FWFT feature set flags
> + *
> + * Return: 0 on success, appropriate linux error code otherwise.
> + */
> +int sbi_fwft_set(u32 feature, unsigned long value, unsigned long flags)
> +{
> + return -EOPNOTSUPP;
> +}
> +
> +struct fwft_set_req {
> + u32 feature;
> + unsigned long value;
> + unsigned long flags;
> + atomic_t error;
> +};
> +
> +static void cpu_sbi_fwft_set(void *arg)
> +{
> + struct fwft_set_req *req = arg;
> + int ret;
> +
> + ret = sbi_fwft_set(req->feature, req->value, req->flags);
> + if (ret)
> + atomic_set(&req->error, ret);
What happens when cpuX executed first reported an error but cpuY
executed this function later and report success.
The error will be masked in that case.
> +}
> +
> +/**
> + * sbi_fwft_set_cpumask() - Set a feature for the specified cpumask
> + * @mask: CPU mask of cpus that need the feature to be set
> + * @feature: The feature ID to be set
> + * @value: The feature value to be set
> + * @flags: FWFT feature set flags
> + *
> + * Return: 0 on success, appropriate linux error code otherwise.
> + */
> +int sbi_fwft_set_cpumask(const cpumask_t *mask, u32 feature,
> + unsigned long value, unsigned long flags)
> +{
> + struct fwft_set_req req = {
> + .feature = feature,
> + .value = value,
> + .flags = flags,
> + .error = ATOMIC_INIT(0),
> + };
> +
> + if (feature & SBI_FWFT_GLOBAL_FEATURE_BIT)
> + return -EINVAL;
> +
> + on_each_cpu_mask(mask, cpu_sbi_fwft_set, &req, 1);
> +
> + return atomic_read(&req.error);
> +}
> +
> /**
> * sbi_set_timer() - Program the timer for next timer event.
> * @stime_value: The value after which next timer event should fire.
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