[PATCH v2 1/3] RISC-V: KVM: Add SBI extension validate callback

[Anup Patel]

On Mon, Jul 6, 2026 at 7:42 AM Inochi Amaoto <inochiama at gmail.com> wrote:
>
> When user disable FWFT extension after setting any value of the
> FWFT feature, the state of vCPU will be broken since the value
> of disable FWFT feature is still functional.
>
> Add the generic SBI extension validate callback so the FWFT
> extension can fix its parameters before the first run.
>
> Signed-off-by: Inochi Amaoto <inochiama at gmail.com>

LGTM.

Reviewed-by: Anup Patel <anup at brainfault.org>

Thanks,
Anup

> ---
>  arch/riscv/include/asm/kvm_vcpu_sbi.h |  4 ++++
>  arch/riscv/kvm/vcpu_config.c          |  2 ++
>  arch/riscv/kvm/vcpu_sbi.c             | 23 +++++++++++++++++++++++
>  3 files changed, 29 insertions(+)
>
> diff --git a/arch/riscv/include/asm/kvm_vcpu_sbi.h b/arch/riscv/include/asm/kvm_vcpu_sbi.h
> index c1a7e3b40d9c..f01a2860c751 100644
> --- a/arch/riscv/include/asm/kvm_vcpu_sbi.h
> +++ b/arch/riscv/include/asm/kvm_vcpu_sbi.h
> @@ -60,6 +60,9 @@ struct kvm_vcpu_sbi_extension {
>
>         void (*reset)(struct kvm_vcpu *vcpu);
>
> +       /* Allow the extension to correct its parameters before the first run */
> +       void (*validate)(struct kvm_vcpu *vcpu);
> +
>         unsigned long state_reg_subtype;
>         unsigned long (*get_state_reg_count)(struct kvm_vcpu *vcpu);
>         int (*get_state_reg_id)(struct kvm_vcpu *vcpu, int index, u64 *reg_id);
> @@ -93,6 +96,7 @@ int kvm_riscv_vcpu_sbi_ecall(struct kvm_vcpu *vcpu, struct kvm_run *run);
>  void kvm_riscv_vcpu_sbi_init(struct kvm_vcpu *vcpu);
>  void kvm_riscv_vcpu_sbi_deinit(struct kvm_vcpu *vcpu);
>  void kvm_riscv_vcpu_sbi_reset(struct kvm_vcpu *vcpu);
> +void kvm_riscv_vcpu_sbi_validate(struct kvm_vcpu *vcpu);
>
>  #ifdef CONFIG_RISCV_SBI_V01
>  extern const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_v01;
> diff --git a/arch/riscv/kvm/vcpu_config.c b/arch/riscv/kvm/vcpu_config.c
> index 238418fed2b9..b68aa830aaf5 100644
> --- a/arch/riscv/kvm/vcpu_config.c
> +++ b/arch/riscv/kvm/vcpu_config.c
> @@ -69,6 +69,8 @@ void kvm_riscv_vcpu_config_ran_once(struct kvm_vcpu *vcpu)
>
>         if (vcpu->guest_debug)
>                 cfg->hedeleg &= ~BIT(EXC_BREAKPOINT);
> +
> +       kvm_riscv_vcpu_sbi_validate(vcpu);
>  }
>
>  void kvm_riscv_vcpu_config_load(struct kvm_vcpu *vcpu)
> diff --git a/arch/riscv/kvm/vcpu_sbi.c b/arch/riscv/kvm/vcpu_sbi.c
> index 46ab7b989432..b737e9a7a12a 100644
> --- a/arch/riscv/kvm/vcpu_sbi.c
> +++ b/arch/riscv/kvm/vcpu_sbi.c
> @@ -723,3 +723,26 @@ void kvm_riscv_vcpu_sbi_reset(struct kvm_vcpu *vcpu)
>                 ext->reset(vcpu);
>         }
>  }
> +
> +void kvm_riscv_vcpu_sbi_validate(struct kvm_vcpu *vcpu)
> +{
> +       struct kvm_vcpu_sbi_context *scontext = &vcpu->arch.sbi_context;
> +       const struct kvm_riscv_sbi_extension_entry *entry;
> +       const struct kvm_vcpu_sbi_extension *ext;
> +       int idx, i;
> +
> +       for (i = 0; i < ARRAY_SIZE(sbi_ext); i++) {
> +               entry = &sbi_ext[i];
> +               ext = entry->ext_ptr;
> +               idx = entry->ext_idx;
> +
> +               if (idx < 0 || idx >= ARRAY_SIZE(scontext->ext_status))
> +                       continue;
> +
> +               if (scontext->ext_status[idx] != KVM_RISCV_SBI_EXT_STATUS_ENABLED ||
> +                   !ext->validate)
> +                       continue;
> +
> +               ext->validate(vcpu);
> +       }
> +}
> --
> 2.55.0
>