RISC-V: KVM: Don't treat SBI HFENCE calls as NOPs

[ Upstream commit 2e7be162996640bbe3b6da694cc064c511b8a5d9 ]

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")
Reviewed-by: Atish Patra <atishp@rivosinc.com>
Signed-off-by: Anup Patel <apatel@ventanamicro.com>
Link: https://lore.kernel.org/r/20250605061458.196003-3-apatel@ventanamicro.com
Signed-off-by: Anup Patel <anup@brainfault.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/arch/riscv/kvm/vcpu_sbi_replace.c b/arch/riscv/kvm/vcpu_sbi_replace.c
index 304d29383e6c0e487b3ec34330e29c0b3b06d7a8..1b8b3fa5f74ab533c9d0a76f7797bee0a9b34266 100644 (file)
--- a/arch/riscv/kvm/vcpu_sbi_replace.c
+++ b/arch/riscv/kvm/vcpu_sbi_replace.c
@@ -113,9 +113,9 @@ 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:
                ret = -EOPNOTSUPP;
        }