[PATCH v5 03/13] riscv: sbi: add FWFT extension interface

Clément Léger
2025-04-17T12:36:12Z

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@rivosinc.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.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..c8eab315c80e 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_local_set_cpumask(const cpumask_t *mask, u32 feature,
+ unsigned long value, unsigned long flags);
+/**
+ * sbi_fwft_local_set() - 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_local_set(u32 feature, unsigned long value,
+ unsigned long flags)
+{
+ return sbi_fwft_local_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 1989b8cade1b..379981c2bb21 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);
+}
+
+/**
+ * sbi_fwft_local_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_local_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.