[PATCH v2 2/7] KVM: x86: hyper-v: disallow configuring SynIC timers with no SynIC

[Vitaly Kuznetsov]

Hyper-V Synthetic timers require SynIC but we don't seem to check that
upon HV_X64_MSR_STIMER[X]_CONFIG/HV_X64_MSR_STIMER0_COUNT writes. Make
the behavior match synic_set_msr().

Signed-off-by: Vitaly Kuznetsov <vkuzn...@redhat.com>
---
 arch/x86/kvm/hyperv.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index 814d3aee5cef..9527fa9685ad 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -633,6 +633,11 @@ 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 = stimer_to_vcpu(stimer);
+       struct kvm_vcpu_hv_synic *synic = vcpu_to_synic(vcpu);
+
+       if (!synic->active && !host)
+               return 1;
 
        trace_kvm_hv_stimer_set_config(stimer_to_vcpu(stimer)->vcpu_id,
                                       stimer->index, config, host);
@@ -652,6 +657,12 @@ static int stimer_set_config(struct kvm_vcpu_hv_stimer 
*stimer, u64 config,
 static int stimer_set_count(struct kvm_vcpu_hv_stimer *stimer, u64 count,
                            bool host)
 {
+       struct kvm_vcpu *vcpu = stimer_to_vcpu(stimer);
+       struct kvm_vcpu_hv_synic *synic = vcpu_to_synic(vcpu);
+
+       if (!synic->active && !host)
+               return 1;
+
        trace_kvm_hv_stimer_set_count(stimer_to_vcpu(stimer)->vcpu_id,
                                      stimer->index, count, host);
 
-- 
2.25.4