RISC-V: KVM: Implement SBI HSM suspend call

The SBI v0.3 specification extends SBI HSM extension by adding SBI HSM
suspend call and related HART states. This patch extends the KVM RISC-V
HSM implementation to provide KVM guest a minimal SBI HSM suspend call
which is equivalent to a WFI instruction.

Signed-off-by: Anup Patel <apatel@ventanamicro.com>
Reviewed-by: Atish Patra <atishp@rivosinc.com>
Signed-off-by: Anup Patel <anup@brainfault.org>

arch/riscv/kvm/vcpu_sbi_hsm.c

@@ -61,6 +61,8 @@ static int kvm_sbi_hsm_vcpu_get_status(struct kvm_vcpu *vcpu)
 		return -EINVAL;
 	if (!target_vcpu->arch.power_off)
 		return SBI_HSM_STATE_STARTED;
+	else if (vcpu->stat.generic.blocking)
+		return SBI_HSM_STATE_SUSPENDED;
 	else
 		return SBI_HSM_STATE_STOPPED;
 }
@@ -91,6 +93,18 @@ static int kvm_sbi_ext_hsm_handler(struct kvm_vcpu *vcpu, struct kvm_run *run,
 			ret = 0;
 		}
 		break;
+	case SBI_EXT_HSM_HART_SUSPEND:
+		switch (cp->a0) {
+		case SBI_HSM_SUSPEND_RET_DEFAULT:
+			kvm_riscv_vcpu_wfi(vcpu);
+			break;
+		case SBI_HSM_SUSPEND_NON_RET_DEFAULT:
+			ret = -EOPNOTSUPP;
+			break;
+		default:
+			ret = -EINVAL;
+		}
+		break;
 	default:
 		ret = -EOPNOTSUPP;
 	}