Synthetic timers MSRs (HV_X64_MSR_STIMER[0-3]_CONFIG,
HV_X64_MSR_STIMER[0-3]_COUNT) are only available to guest when
HV_MSR_SYNTIMER_AVAILABLE bit is exposed.

While on it, complement stimer_get_config()/stimer_get_count() with
the same '!synic->active' check we have in stimer_set_config()/
stimer_set_count().

Signed-off-by: Vitaly Kuznetsov <vkuzn...@redhat.com>
---
 arch/x86/kvm/hyperv.c | 34 ++++++++++++++++++++++++++++------
 1 file changed, 28 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index d85c441011c4..032305ad5615 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -637,7 +637,9 @@ static int stimer_set_config(struct kvm_vcpu_hv_stimer 
*stimer, u64 config,
        struct kvm_vcpu *vcpu = hv_stimer_to_vcpu(stimer);
        struct kvm_vcpu_hv_synic *synic = to_hv_synic(vcpu);
 
-       if (!synic->active && !host)
+       if (unlikely(!host && (!synic->active ||
+                              !(to_hv_vcpu(vcpu)->cpuid_cache.features_eax &
+                                HV_MSR_SYNTIMER_AVAILABLE))))
                return 1;
 
        trace_kvm_hv_stimer_set_config(hv_stimer_to_vcpu(stimer)->vcpu_id,
@@ -661,7 +663,9 @@ static int stimer_set_count(struct kvm_vcpu_hv_stimer 
*stimer, u64 count,
        struct kvm_vcpu *vcpu = hv_stimer_to_vcpu(stimer);
        struct kvm_vcpu_hv_synic *synic = to_hv_synic(vcpu);
 
-       if (!synic->active && !host)
+       if (unlikely(!host && (!synic->active ||
+                              !(to_hv_vcpu(vcpu)->cpuid_cache.features_eax &
+                                HV_MSR_SYNTIMER_AVAILABLE))))
                return 1;
 
        trace_kvm_hv_stimer_set_count(hv_stimer_to_vcpu(stimer)->vcpu_id,
@@ -680,14 +684,32 @@ static int stimer_set_count(struct kvm_vcpu_hv_stimer 
*stimer, u64 count,
        return 0;
 }
 
-static int stimer_get_config(struct kvm_vcpu_hv_stimer *stimer, u64 *pconfig)
+static int stimer_get_config(struct kvm_vcpu_hv_stimer *stimer, u64 *pconfig,
+                            bool host)
 {
+       struct kvm_vcpu *vcpu = hv_stimer_to_vcpu(stimer);
+       struct kvm_vcpu_hv_synic *synic = to_hv_synic(vcpu);
+
+       if (unlikely(!host && (!synic->active ||
+                              !(to_hv_vcpu(vcpu)->cpuid_cache.features_eax &
+                                HV_MSR_SYNTIMER_AVAILABLE))))
+               return 1;
+
        *pconfig = stimer->config.as_uint64;
        return 0;
 }
 
-static int stimer_get_count(struct kvm_vcpu_hv_stimer *stimer, u64 *pcount)
+static int stimer_get_count(struct kvm_vcpu_hv_stimer *stimer, u64 *pcount,
+                           bool host)
 {
+       struct kvm_vcpu *vcpu = hv_stimer_to_vcpu(stimer);
+       struct kvm_vcpu_hv_synic *synic = to_hv_synic(vcpu);
+
+       if (unlikely(!host && (!synic->active ||
+                              !(to_hv_vcpu(vcpu)->cpuid_cache.features_eax &
+                                HV_MSR_SYNTIMER_AVAILABLE))))
+               return 1;
+
        *pcount = stimer->count;
        return 0;
 }
@@ -1571,7 +1593,7 @@ static int kvm_hv_get_msr(struct kvm_vcpu *vcpu, u32 msr, 
u64 *pdata,
                int timer_index = (msr - HV_X64_MSR_STIMER0_CONFIG)/2;
 
                return stimer_get_config(to_hv_stimer(vcpu, timer_index),
-                                        pdata);
+                                        pdata, host);
        }
        case HV_X64_MSR_STIMER0_COUNT:
        case HV_X64_MSR_STIMER1_COUNT:
@@ -1580,7 +1602,7 @@ static int kvm_hv_get_msr(struct kvm_vcpu *vcpu, u32 msr, 
u64 *pdata,
                int timer_index = (msr - HV_X64_MSR_STIMER0_COUNT)/2;
 
                return stimer_get_count(to_hv_stimer(vcpu, timer_index),
-                                       pdata);
+                                       pdata, host);
        }
        case HV_X64_MSR_TSC_FREQUENCY:
                data = (u64)vcpu->arch.virtual_tsc_khz * 1000;
-- 
2.30.2

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