Re: [PATCH 02/13] RISC-V: KVM: Don't treat SBI HFENCE calls as NOPs

[Anup Patel]

On Thu, Jun 5, 2025 at 11:45 AM Anup Patel <apatel@xxxxxxxxxxxxxxxx> wrote:
>
> The SBI specification clearly states that SBI HFENCE calls should
> return SBI_ERR_NOT_SUPPORTED when one of the target hart doesn’t
> support hypervisor extension (aka nested virtualization in-case
> of KVM RISC-V).
>
> Fixes: c7fa3c48de86 ("RISC-V: KVM: Treat SBI HFENCE calls as NOPs")
> Signed-off-by: Anup Patel <apatel@xxxxxxxxxxxxxxxx>

Queued as a fix for Linux-6.16

Regards,
Anup

> ---
>  arch/riscv/kvm/vcpu_sbi_replace.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/arch/riscv/kvm/vcpu_sbi_replace.c b/arch/riscv/kvm/vcpu_sbi_replace.c
> index 9752d2ffff68..b17fad091bab 100644
> --- a/arch/riscv/kvm/vcpu_sbi_replace.c
> +++ b/arch/riscv/kvm/vcpu_sbi_replace.c
> @@ -127,9 +127,9 @@ static int kvm_sbi_ext_rfence_handler(struct kvm_vcpu *vcpu, struct kvm_run *run
>         case SBI_EXT_RFENCE_REMOTE_HFENCE_VVMA_ASID:
>                 /*
>                  * Until nested virtualization is implemented, the
> -                * SBI HFENCE calls should be treated as NOPs
> +                * SBI HFENCE calls should return not supported
> +                * hence fallthrough.
>                  */
> -               break;
>         default:
>                 retdata->err_val = SBI_ERR_NOT_SUPPORTED;
>         }
> --
> 2.43.0
>