The patch below does not apply to the 4.9-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From b1e34d325397a33d97d845e312d7cf2a8b646b44 Mon Sep 17 00:00:00 2001 From: Vitaly Kuznetsov vkuznets@redhat.com Date: Fri, 25 Mar 2022 14:21:40 +0100 Subject: [PATCH] KVM: x86: Forbid VMM to set SYNIC/STIMER MSRs when SynIC wasn't activated
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
diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c index f715b5a2b0e4..4177c17a26bf 100644 --- a/arch/x86/kvm/hyperv.c +++ b/arch/x86/kvm/hyperv.c @@ -239,7 +239,7 @@ static int synic_set_msr(struct kvm_vcpu_hv_synic *synic, struct kvm_vcpu *vcpu = hv_synic_to_vcpu(synic); int ret;
- if (!synic->active && !host) + if (!synic->active && (!host || data)) return 1;
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: { int i;
+ if (!synic->active) + break; + for (i = 0; i < ARRAY_SIZE(synic->sint); i++) kvm_hv_notify_acked_sint(vcpu, i); 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_synic *synic = to_hv_synic(vcpu);
- if (!synic->active && !host) + if (!synic->active && (!host || config)) return 1;
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_hv_synic *synic = to_hv_synic(vcpu);
- if (!synic->active && !host) + if (!synic->active && (!host || count)) return 1;
trace_kvm_hv_stimer_set_count(hv_stimer_to_vcpu(stimer)->vcpu_id,