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KVM: x86: Forbid VMM to set SYNIC/STIMER MSRs when SynIC wasn't activated

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Setting non-zero values to SYNIC/STIMER MSRs activates certain features,
this should not happen when KVM_CAP_HYPERV_SYNIC{,2} was not activated.

Note, it would've been better to forbid writing anything to SYNIC/STIMER
MSRs, including zeroes, however, at least QEMU tries clearing
HV_X64_MSR_STIMER0_CONFIG without SynIC. HV_X64_MSR_EOM MSR is somewhat
'special' as writing zero there triggers an action, this also should not
happen when SynIC wasn't activated.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Message-Id: <20220325132140.25650-4-vkuznets@redhat.com>
Cc: stable@vger.kernel.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Vitaly Kuznetsov 2022-03-25 14:21:40 +01:00 committed by Paolo Bonzini
parent 00b5f37189
commit b1e34d3253
1 changed files with 6 additions and 3 deletions
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9
arch/x86/kvm/hyperv.c
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@ -239,7 +239,7 @@ static int synic_set_msr(struct kvm_vcpu_hv_synic *synic,
struct kvm_vcpu *vcpu = hv_synic_to_vcpu(synic); struct kvm_vcpu *vcpu = hv_synic_to_vcpu(synic);
int ret; int ret;
if (!synic->active && !host) if (!synic->active && (!host || data))
return 1; return 1;
trace_kvm_hv_synic_set_msr(vcpu->vcpu_id, msr, data, host); trace_kvm_hv_synic_set_msr(vcpu->vcpu_id, msr, data, host);
@ -285,6 +285,9 @@ static int synic_set_msr(struct kvm_vcpu_hv_synic *synic,
case HV_X64_MSR_EOM: { case HV_X64_MSR_EOM: {
int i; int i;
if (!synic->active)
break;
for (i = 0; i < ARRAY_SIZE(synic->sint); i++) for (i = 0; i < ARRAY_SIZE(synic->sint); i++)
kvm_hv_notify_acked_sint(vcpu, i); kvm_hv_notify_acked_sint(vcpu, i);
break; break;
@ -664,7 +667,7 @@ static int stimer_set_config(struct kvm_vcpu_hv_stimer *stimer, u64 config,
struct kvm_vcpu_hv *hv_vcpu = to_hv_vcpu(vcpu); struct kvm_vcpu_hv *hv_vcpu = to_hv_vcpu(vcpu);
struct kvm_vcpu_hv_synic *synic = to_hv_synic(vcpu); struct kvm_vcpu_hv_synic *synic = to_hv_synic(vcpu);
if (!synic->active && !host) if (!synic->active && (!host || config))
return 1; return 1;
if (unlikely(!host && hv_vcpu->enforce_cpuid && new_config.direct_mode && if (unlikely(!host && hv_vcpu->enforce_cpuid && new_config.direct_mode &&
@ -693,7 +696,7 @@ 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 *vcpu = hv_stimer_to_vcpu(stimer);
struct kvm_vcpu_hv_synic *synic = to_hv_synic(vcpu); struct kvm_vcpu_hv_synic *synic = to_hv_synic(vcpu);
if (!synic->active && !host) if (!synic->active && (!host || count))
return 1; return 1;
trace_kvm_hv_stimer_set_count(hv_stimer_to_vcpu(stimer)->vcpu_id, trace_kvm_hv_stimer_set_count(hv_stimer_to_vcpu(stimer)->vcpu_id,