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

From: Vitaly Kuznetsov
Date: Fri Aug 07 2020 - 04:40:11 EST


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@xxxxxxxxxx>
---
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 af9cdb426dd2..4291943d1028 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