KVM: x86: hyper-v: disallow configuring SynIC timers with no SynIC

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 <vkuznets@redhat.com>
Message-Id: <20200924145757.1035782-3-vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index 1d330564eed8ca2bf5995f587dc2f9d4a2caf2d4..67a4f60a89b58bce7cf993818be1e8ac82fab2c6 100644 (file)
--- 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);