KVM: x86: mark hyper-v vapic assist page as dirty

Signed-off-by: NVadim Rozenfeld <vrozenfe@redhat.com>
Reviewed-by: NMarcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/x86.c

@@ -1869,19 +1869,21 @@ static int set_msr_hyperv(struct kvm_vcpu *vcpu, u32 msr, u64 data)
 {
 	switch (msr) {
 	case HV_X64_MSR_APIC_ASSIST_PAGE: {
+		u64 gfn;
 		unsigned long addr;
 
 		if (!(data & HV_X64_MSR_APIC_ASSIST_PAGE_ENABLE)) {
 			vcpu->arch.hv_vapic = data;
 			break;
 		}
-		addr = gfn_to_hva(vcpu->kvm, data >>
-				  HV_X64_MSR_APIC_ASSIST_PAGE_ADDRESS_SHIFT);
+		gfn = data >> HV_X64_MSR_APIC_ASSIST_PAGE_ADDRESS_SHIFT;
+		addr = gfn_to_hva(vcpu->kvm, gfn);
 		if (kvm_is_error_hva(addr))
 			return 1;
 		if (__clear_user((void __user *)addr, PAGE_SIZE))
 			return 1;
 		vcpu->arch.hv_vapic = data;
+		mark_page_dirty(vcpu->kvm, gfn);
 		break;
 	}
 	case HV_X64_MSR_EOI: