From d2547cf59793168b564372d75620897416cbaf87 Mon Sep 17 00:00:00 2001 From: Vitaly Kuznetsov Date: Tue, 16 Mar 2021 15:37:33 +0100 Subject: KVM: x86: hyper-v: Limit guest to writing zero to HV_X64_MSR_TSC_EMULATION_STATUS HV_X64_MSR_TSC_EMULATION_STATUS indicates whether TSC accesses are emulated after migration (to accommodate for a different host TSC frequency when TSC scaling is not supported; we don't implement this in KVM). Guest can use the same MSR to stop TSC access emulation by writing zero. Writing anything else is forbidden. Signed-off-by: Vitaly Kuznetsov Message-Id: <20210316143736.964151-2-vkuznets@redhat.com> Signed-off-by: Paolo Bonzini --- arch/x86/kvm/hyperv.c | 3 +++ 1 file changed, 3 insertions(+) (limited to 'arch') diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c index 58fa8c029867..eefb85b86fe8 100644 --- a/arch/x86/kvm/hyperv.c +++ b/arch/x86/kvm/hyperv.c @@ -1229,6 +1229,9 @@ static int kvm_hv_set_msr_pw(struct kvm_vcpu *vcpu, u32 msr, u64 data, hv->hv_tsc_emulation_control = data; break; case HV_X64_MSR_TSC_EMULATION_STATUS: + if (data && !host) + return 1; + hv->hv_tsc_emulation_status = data; break; case HV_X64_MSR_TIME_REF_COUNT: -- cgit v1.2.3