KVM: x86: hyper-v: Honor HV_STIMER_DIRECT_MODE_AVAILABLE privilege bit

Synthetic timers can only be configured in 'direct' mode when
HV_STIMER_DIRECT_MODE_AVAILABLE bit was exposed.
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20210521095204.2161214-20-vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/hyperv.c

@@ -631,11 +631,17 @@ static int stimer_set_config(struct kvm_vcpu_hv_stimer *stimer, u64 config,
 	union hv_stimer_config new_config = {.as_uint64 = config},
 		old_config = {.as_uint64 = stimer->config.as_uint64};
 	struct kvm_vcpu *vcpu = hv_stimer_to_vcpu(stimer);
+	struct kvm_vcpu_hv *hv_vcpu = to_hv_vcpu(vcpu);
 	struct kvm_vcpu_hv_synic *synic = to_hv_synic(vcpu);
 
 	if (!synic->active && !host)
 		return 1;
 
+	if (unlikely(!host && hv_vcpu->enforce_cpuid && new_config.direct_mode &&
+		     !(hv_vcpu->cpuid_cache.features_edx &
+		       HV_STIMER_DIRECT_MODE_AVAILABLE)))
+		return 1;
+
 	trace_kvm_hv_stimer_set_config(hv_stimer_to_vcpu(stimer)->vcpu_id,
 				       stimer->index, config, host);